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Testing of Materials and Elements in Civil Engineering (2nd Edition)

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Construction and Building Materials".

Deadline for manuscript submissions: closed (10 November 2022) | Viewed by 125225

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Krzysztof Schabowicz

E-Mail Website
Guest Editor
Faculty of Civil Engineering W2/Z1, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wrocław, Poland
Interests: nondestructive testing of building materials and elements; ultrasonic tomography in civil engineering; analysis of CT images obtained with ultrasound; computer knowledge representation of building materials and elements using nondestructive testing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Last year, we ran a successful Special Issue on “Testing of Materials and Elements in Civil Engineering”, with over 50 papers published. The field of materials testing in civil engineering is very wide and interesting from an engineering and scientific point of view. Therefore, we have decided make a second edition dedicated to this topic.

This new Issue is proposed and organized as a means to present recent developments in the field of materials testing in civil engineering. The articles highlighted in this Issue should relate to different aspects of the testing of different materials in civil engineering, from building materials and elements to building structures. The current trend in the development of materials testing in civil engineering is mainly concerned with the detection of flaws and defects in elements and structures using destructive, semidestructive, and nondestructive testing.

It is my pleasure to invite you to submit a manuscript for this Special Issue mainly focused on novel different testing approaches, the development of single and hybrid measurement techniques, and advanced signal analysis.

The topics of interest include but are not limited to:

  • Testing of materials and elements in civil engineering;
  • Testing of structures made of novel materials;
  • Condition assessment of civil materials and elements;
  • Detecting defects that are invisible on the surface;
  • Damage detection and damage imaging;
  • Diagnostics of cultural heritage monuments;
  • Structural health monitoring systems;
  • Modeling and numerical analyses;
  • Nondestructive testing methods;
  • Advanced signal processing for nondestructive testing.

Prof. Dr. Krzysztof Schabowicz
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • testing
  • diagnostics
  • building materials
  • elements
  • civil engineering

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Published Papers (61 papers)

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16 pages, 4195 KiB  
Article
Continuous Evaluation of Shear Wave Velocity from Bender Elements during Monotonic Triaxial Loading
by Ahmed Khalil, Zahid Khan, Mousa Attom, Kazi Fattah, Tarig Ali and Maruf Mortula
Materials 2023, 16(2), 766; https://doi.org/10.3390/ma16020766 - 12 Jan 2023
Cited by 2 | Viewed by 1220
Abstract
Few researchers have attempted to experimentally evaluate the low-strain shear wave velocity (Vs) of specimens undergoing large strain deformations. They report that the Vs is practically unaffected by the strains, and the reasons behind this behavior are not fully understood. This [...] Read more.
Few researchers have attempted to experimentally evaluate the low-strain shear wave velocity (Vs) of specimens undergoing large strain deformations. They report that the Vs is practically unaffected by the strains, and the reasons behind this behavior are not fully understood. This study presents the continuous measurement of low-strain Vs with bender elements (BE) during monotonic shearing of two sand specimens in a triaxial device. The results are analyzed using a micro-mechanical model based on contact theory. The results of this study confirm that the Vs values from BE measurements are unaffected by an increase in axial strains that are induced by a separate mechanism. The micro-mechanical model predictions of Vs agree well with the results of this study and with the results of previous studies. They show that the mean effective stress and increase in inter-particle stiffness controls the low-strain stiffness despite a global increase in strains during monotonic loading. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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27 pages, 7472 KiB  
Article
Statistical Quality Inspection Methodology in Production of Precast Concrete Elements
by Izabela Skrzypczak
Materials 2023, 16(1), 431; https://doi.org/10.3390/ma16010431 - 02 Jan 2023
Cited by 2 | Viewed by 2127
Abstract
Today, prefabricated concrete elements are used in many construction areas, including in industrial, public, and residential construction; this was confirmed via questionnaire research. In the article, the prospects for precast concrete development are presented, and the factors determining the use of this technology [...] Read more.
Today, prefabricated concrete elements are used in many construction areas, including in industrial, public, and residential construction; this was confirmed via questionnaire research. In the article, the prospects for precast concrete development are presented, and the factors determining the use of this technology are defined. Based on a review of the literature, it was shown that currently, higher-quality prefabricated elements are primarily created through the implementation of innovative materials and production technologies. For this reason, the lack of research regarding quality control in prefabricated elements based on statistical quality control is particularly noticeable. The quality control process is one of the most important distinguishing features in prefabrication due to the increasingly stringent expectations of customers; it helps to ensure that the desired durability of implemented constructions is achieved. Issues related to assessing the effectiveness of standard procedures presented in this paper were analyzed using statistical methods in the form of OC (operating characteristic) and AOQ (average outgoing quality) curves. Thus, a new approach was proposed because these methods have not been previously used in precast concrete. The shape of the curves obtained confirmed the significant dependence of the value of the acceptance probability on the defectiveness of production. In AQL control systems based on OC and AOQ curves, it is necessary to calculate the current average defectiveness, which should be treated as a basis for the decision to switch from one type of control (normal, tightened, or reduced) to another. In this respect, the standard requirements of quality control have been simplified, and it has not been considered necessary to determine the average defectiveness value in production processes. The examples included in this study, including the analysis of curb production data, clearly show the harmful effects of ignoring the actual process defectiveness. As a result of the calculations, it was found that the average actual defectiveness of the curbs produced could not be equated with batch defectiveness. The analyses carried out in this study prove that equating batch defectiveness with process defectiveness is not an appropriate approach, which was confirmed through the producer’s/customer’s risk analysis. The approach proposed in this study, the analysis of OC and AOQ curves, is an innovative solution in prefabrication and can be an effective tool for managing the quality of prefabricated products, taking into account economic boundary conditions. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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14 pages, 2528 KiB  
Article
Effects of Field Aging on Material Properties and Rutting Performance of Asphalt Pavement
by Haoyang Wang, Yu Zhu, Weiguang Zhang, Shihui Shen, Shenghua Wu, Louay N. Mohammad and Xuhui She
Materials 2023, 16(1), 225; https://doi.org/10.3390/ma16010225 - 26 Dec 2022
Cited by 3 | Viewed by 1351
Abstract
This study evaluates field asphalt aging based on material property changes in pavement with time, and investigates if such changes could have an impact on field rutting performance. Four projects from three different climate zones were monitored as part of the NCHRP 9–49A [...] Read more.
This study evaluates field asphalt aging based on material property changes in pavement with time, and investigates if such changes could have an impact on field rutting performance. Four projects from three different climate zones were monitored as part of the NCHRP 9–49A project at two stages: during pavement construction and two to three years after opening it to traffic. Construction information were collected, and field cores were drilled at both stages to evaluate the material properties of recovered asphalt binder and asphalt mixture. Field rut depth was also measured. In addition, pavement structure, climate and base/subgrade modulus information were also obtained. Results indicate that the asphalt mixture stiffening is caused in major part by asphalt aging. However, the effect of asphalt aging on pavement mixture property may not follow a proportional liner trend. The parameters that are most sensitive to field ageing are MSCR R3.2 and dynamic modulus. It is also found that the variables which showed a good ranking trend with the field rut depth are climate condition (relative humidity, high temperature hour, solar radiation), material properties (Hamburg rut depth, rutting resistance index, high temperature performance grade, MSCR, and dynamic modulus, base and subgrade moduli), as well as air voids. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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19 pages, 2497 KiB  
Article
An Efficient Method for Optimizing HPC-FRP Retrofit Systems of Flexural Strengthened One-Way Continuous Slabs Based on ACI 440.2R
by Huy Q. Nguyen, Kijae Yang and Jung J. Kim
Materials 2022, 15(23), 8430; https://doi.org/10.3390/ma15238430 - 26 Nov 2022
Cited by 1 | Viewed by 1121
Abstract
An innovative retrofit system consisting of fiber-reinforced polymers (FRP) and high-performance concrete (HPC) considering the difficulty of the accessibility and installation of FRP on the underside of reinforced concrete (RC) slabs was found to be efficient in the flexural strengthening of existing RC [...] Read more.
An innovative retrofit system consisting of fiber-reinforced polymers (FRP) and high-performance concrete (HPC) considering the difficulty of the accessibility and installation of FRP on the underside of reinforced concrete (RC) slabs was found to be efficient in the flexural strengthening of existing RC slabs. It is important to note that continuous slabs using the FRP-HPC retrofit systems are less effective in exploiting FRP tensile strength and can cause sudden failure once excessively enhanced flexural strength exceeds shear strength. A design method to ensure ductile failure mode was also proposed for strengthened continuous RC slabs in the previous literature. Thus, it is necessary to optimize retrofit systems in terms of mechanical performance aspects to improve the efficiency of retrofitted slabs in serviceability. This study proposes a design method for optimizing the strength of materials and inducing ductile failure of continuous slab retrofitting FRP-HPC systems. The proposed approach demonstrated its effectiveness for strengthening a continuous RC slab with various FRP-HPC retrofit systems through a case study. The results show that the design factored load in the serviceability limit state does not change appreciably from a decrease in carbon fiber-reinforced polymers (CFRP) of 38%; the design factored load decreased only by 9% and the ultimate failure load by 13% while reducing CFRP by 20% and HPC by 25%. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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21 pages, 9166 KiB  
Article
Application of Soft-Computing Methods to Evaluate the Compressive Strength of Self-Compacting Concrete
by Muhammad Nasir Amin, Mohammed Najeeb Al-Hashem, Ayaz Ahmad, Kaffayatullah Khan, Waqas Ahmad, Muhammad Ghulam Qadir, Muhammad Imran and Qasem M. S. Al-Ahmad
Materials 2022, 15(21), 7800; https://doi.org/10.3390/ma15217800 - 04 Nov 2022
Cited by 9 | Viewed by 1734
Abstract
This research examined machine learning (ML) techniques for predicting the compressive strength (CS) of self-compacting concrete (SCC). Multilayer perceptron (MLP), bagging regressor (BR), and support vector machine (SVM) were utilized for analysis. A total of 169 data points were retrieved from the various [...] Read more.
This research examined machine learning (ML) techniques for predicting the compressive strength (CS) of self-compacting concrete (SCC). Multilayer perceptron (MLP), bagging regressor (BR), and support vector machine (SVM) were utilized for analysis. A total of 169 data points were retrieved from the various published articles. The data set was based on 11 input parameters, such as cement, limestone, fly ash, ground granulated blast-furnace slag, silica fume, rice husk ash, coarse aggregate, fine aggregate, superplasticizers, water, viscosity modifying admixtures, and one output with compressive strength of SCC. In terms of properly predicting the CS of SCC, the BR technique outperformed both the SVM and MLP models, as determined by the research results. In contrast to SVM and MLP, the coefficient of determination (R2) for the BR model was 0.95, whereas for SVM and MLP, the R2 was 0.90 and 0.86, respectively. In addition, a k-fold cross-validation approach was adopted to check the accuracy of the employed models. The statistical measures mean absolute percent error, mean absolute error, and root mean square error ensure the validity of the model. Using sensitivity analysis, the influence of input factors on the intended CS of SCC was also explored. This analysis reveals that the highest contributing parameter towards the CS of SCC was cement with 16.2%, while rice husk ash contributed the least with 4.25% among all the input variables. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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19 pages, 5218 KiB  
Article
The Effects of Bond–Slip Laws on the Debonding Failure and Behavior of Flexural Strengthened RC Slabs in Hybrid FRP Retrofit Systems
by Huy Q. Nguyen, Tri N. M. Nguyen, Do Hyung Lee and Jung J. Kim
Materials 2022, 15(21), 7453; https://doi.org/10.3390/ma15217453 - 24 Oct 2022
Cited by 2 | Viewed by 1240
Abstract
The hybrid retrofit system using FRP and concrete overlay applied on the top of slabs has proven effective in strengthening and overcoming logistical constraints, compared with conventional strengthening techniques using externally bonded composite materials to the underside of the slabs. Nevertheless, the performance [...] Read more.
The hybrid retrofit system using FRP and concrete overlay applied on the top of slabs has proven effective in strengthening and overcoming logistical constraints, compared with conventional strengthening techniques using externally bonded composite materials to the underside of the slabs. Nevertheless, the performance of retrofitted slabs is governed by debonding failure due to the low bond strength between CFRP and concrete overlay. Thus, this study investigates the behavior of flexural strengthened slabs with FRP retrofit systems and the effect of bond–slip laws on debonding failure. Firstly, two full-scale RC slabs with and without a retrofit system were tested in a four-point bending setup as the control specimens. Then, the same retrofitted slab was simulated by utilizing the commercial program ABAQUS. A sensitivity analysis was conducted to consider the influence of bond–slip laws to predict the failure mechanism of the retrofitted slabs based on load–deflection relationships. The results showed that the strengthened slab enhanced the load-carrying capacity by 59%, stiffness by 111%, and toughness by 29%. The initial stiffness of 0.1K0 and maximum shear stress of 0.13τmax, compared with the corresponding values of Neubauer’s and Rostasy’s bond–slip law, can be used to simulate the global response of the retrofitted slab validated by experiment results. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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20 pages, 6770 KiB  
Article
The Experimental Investigation on Mechanics and Damage Characteristics of the Aeolian Sand Paste-like Backfill Materials Based on Acoustic Emission
by Xiaoping Shao, Chuang Tian, Chao Li, Zhiyu Fang, Bingchao Zhao, Baowa Xu, Jianbo Ning, Longqing Li and Renlong Tang
Materials 2022, 15(20), 7235; https://doi.org/10.3390/ma15207235 - 17 Oct 2022
Cited by 6 | Viewed by 1113
Abstract
With the wide application of the filling mining method, it is necessary to consider the influence of rock activity on the filling body, reflected in the laboratory, that is, the influence of loading rate. Therefore, to explore the response characteristics of loading rate [...] Read more.
With the wide application of the filling mining method, it is necessary to consider the influence of rock activity on the filling body, reflected in the laboratory, that is, the influence of loading rate. Therefore, to explore the response characteristics of loading rate on the mechanical and damage characteristics of aeolian sand paste filling body, DNS100 electronic universal testing machine and DS5-16B acoustic emission (AE) monitoring system were used to monitor the stress–strain changes and AE characteristic parameters changes of aeolian sand paste filling body during uniaxial compression, and the theoretical model of filling sample damage considering loading rate was established based on AE parameters. The experimental results show that: (1) With the increase in loading rate, the uniaxial compressive strength and elastic modulus of aeolian sand paste-like materials (ASPM) specimens are significantly improved. ASPM specimens have ductile failure characteristics, and the failure mode is unidirectional shear failure → tensile failure → bidirectional shear failure. (2) When the loading rate is low, the AE event points of ASPM specimens are more dispersed, and the large energy points are less. At high loading rates, the AE large energy events are more concentrated in the upper part, and the lower part is more distributed. (3) The proportion of the initial active stage is negatively correlated with the loading rate, and the proportion of the active stage is positively correlated with the loading rate. The total number of AE cumulative ringing decreases with the increase in loading rate. (4) Taking time as an intermediate variable, the coupling relationship between ASPM strain considering loading rate and the AE cumulative ringing count is constructed, and the damage and stress coupling model of ASPM specimen considering loading rate is further deduced. Comparing the theoretical model with the experimental results shows that the model can effectively reflect the damage evolution process of ASPM specimens during loading, especially at high loading rates. The research results have significant reference value for subsequent strength design of filling material, selection of laboratory loading rate and quality monitoring, and early warning of filling body in goaf. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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21 pages, 8966 KiB  
Article
Data-Driven Techniques for Evaluating the Mechanical Strength and Raw Material Effects of Steel Fiber-Reinforced Concrete
by Mohammed Najeeb Al-Hashem, Muhammad Nasir Amin, Waqas Ahmad, Kaffayatullah Khan, Ayaz Ahmad, Saqib Ehsan, Qasem M. S. Al-Ahmad and Muhammad Ghulam Qadir
Materials 2022, 15(19), 6928; https://doi.org/10.3390/ma15196928 - 06 Oct 2022
Cited by 3 | Viewed by 1836
Abstract
Estimating concrete properties using soft computing techniques has been shown to be a time and cost-efficient method in the construction industry. Thus, for the prediction of steel fiber-reinforced concrete (SFRC) strength under compressive and flexural loads, the current research employed advanced and effective [...] Read more.
Estimating concrete properties using soft computing techniques has been shown to be a time and cost-efficient method in the construction industry. Thus, for the prediction of steel fiber-reinforced concrete (SFRC) strength under compressive and flexural loads, the current research employed advanced and effective soft computing techniques. In the current study, a single machine learning method known as multiple-layer perceptron neural network (MLPNN) and ensembled machine learning models known as MLPNN-adaptive boosting and MLPNN-bagging are used for this purpose. Water; cement; fine aggregate (FA); coarse aggregate (CA); super-plasticizer (SP); silica fume; and steel fiber volume percent (Vf SF), length (mm), and diameter were the factors considered (mm). This study also employed statistical analysis such as determination coefficient (R2), root mean square error (RMSE), and mean absolute error (MAE) to assess the performance of the algorithms. It was determined that the MLPNN-AdaBoost method is suitable for forecasting SFRC compressive and flexural strengths. The MLPNN technique’s higher R2, i.e., 0.94 and 0.95 for flexural and compressive strength, respectively, and lower error values result in more precision than other methods with lower R2 values. SHAP analysis demonstrated that the volume of cement and steel fibers have the greatest feature values for SFRC’s compressive and flexural strengths, respectively. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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27 pages, 17941 KiB  
Article
A Decision-Making Algorithm for Concrete-Filled Steel Tubular Arch Bridge Maintenance Based on Structural Health Monitoring
by Chengzhong Gui, Weiwei Lin, Zuwei Huang, Guangtao Xin, Jun Xiao and Liuxin Yang
Materials 2022, 15(19), 6920; https://doi.org/10.3390/ma15196920 - 06 Oct 2022
Cited by 1 | Viewed by 2073
Abstract
This study focuses on establishing a novel heuristic algorithm for life-cycle performance evaluation. Special attention is given to decision-making algorithms for concrete-filled steel tubular (CFST) arch bridge maintenance. The main procedure is developed, including the ultimate loading-capacity modeling of CFST members, multi-parameter selection, [...] Read more.
This study focuses on establishing a novel heuristic algorithm for life-cycle performance evaluation. Special attention is given to decision-making algorithms for concrete-filled steel tubular (CFST) arch bridge maintenance. The main procedure is developed, including the ultimate loading-capacity modeling of CFST members, multi-parameter selection, ultimate thresholds presetting based on the finite element method, data processing, crucial parameters determination among sub-parameters, multi-parameter regression, ultimate state prediction, and system maintenance decision-making suggestions based on the multi-parameter performance evaluation. A degenerated ultimate loading-capacity model of CFST members is adopted in the finite element analysis and multi-parameter performance assessment. The multi-source heterogeneous data processing and temperature-effect elimination are performed for the data processing. The key sub-parameters were determined by the Principal Component Analysis method and the Entropy-weight method. The polynomial mathematical model is used in the multi-parameter regression, and the ±95% confidence bounds were verified. The system maintenance decision-making model combines the relative monitoring state, the relative ultimate state by the numerical analysis, and the relative residual life of degenerated members. The optimal system maintenance decision-making suggestions for the bridge maintenance system can be identified, including the most unfavorable maintenance time and parameter index. A case study on a CFST truss-arch bridge is conducted to the proposed algorithms. The obtained results demonstrated that the crack width deserves special attention in concrete bridge maintenance. Additionally, these technologies have enormous potential for the life-cycle performance assessment of the structural health monitoring system for existing concrete bridge structures. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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16 pages, 5254 KiB  
Article
Application of the Acoustic Emission Method and Artificial Neural Networks to Assess the Damaging Effect of High Temperature on the Structure of Fibre-Cement Boards
by Tomasz Gorzelańczyk, Krzysztof Schabowicz and Mateusz Szymków
Materials 2022, 15(18), 6460; https://doi.org/10.3390/ma15186460 - 17 Sep 2022
Cited by 1 | Viewed by 924
Abstract
This article shows the results of research into the damaging effect of high temperature on the structure of fibre-cement boards. Samples of fibre-cement boards were exposed to high temperatures over various lengths of time and then they were investigated under the three-point bending [...] Read more.
This article shows the results of research into the damaging effect of high temperature on the structure of fibre-cement boards. Samples of fibre-cement boards were exposed to high temperatures over various lengths of time and then they were investigated under the three-point bending and acoustic emission methods. In this way, the critical temperature and the duration of its influence on the structure of a fibre-cement board were determined. An artificial neural network was used to analyse the results obtained using the acoustic emission method. The investigations showed a marked fall in the number of registered AE events for the tested series of boards exposed to high temperature in comparison with the reference boards. Moreover, in the boards exposed to high temperature, a marked increase in the energy of AE events occurs during the bending test, whereby the registered events, by and large, come down to a single pulse induced by a brittle fracture. It is also demonstrated that the determination of the damaging effect of high temperature on the structure of fibre-cement boards solely on the basis of bending strength (MOR) is inadequate. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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18 pages, 6971 KiB  
Article
New SHapley Additive ExPlanations (SHAP) Approach to Evaluate the Raw Materials Interactions of Steel-Fiber-Reinforced Concrete
by Madiha Anjum, Kaffayatullah Khan, Waqas Ahmad, Ayaz Ahmad, Muhammad Nasir Amin and Afnan Nafees
Materials 2022, 15(18), 6261; https://doi.org/10.3390/ma15186261 - 09 Sep 2022
Cited by 9 | Viewed by 1906
Abstract
Recently, artificial intelligence (AI) approaches have gained the attention of researchers in the civil engineering field for estimating the mechanical characteristics of concrete to save the effort, time, and cost of researchers. Consequently, the current research focuses on assessing steel-fiber-reinforced concrete (SFRC) in [...] Read more.
Recently, artificial intelligence (AI) approaches have gained the attention of researchers in the civil engineering field for estimating the mechanical characteristics of concrete to save the effort, time, and cost of researchers. Consequently, the current research focuses on assessing steel-fiber-reinforced concrete (SFRC) in terms of flexural strength (FS) prediction by employing delicate AI techniques as well as to predict the raw material interaction that is still a research gap. In this study, the FS of SFRC is estimated by deploying supervised machine learning (ML) techniques, such as DT-Gradient Boosting, DT-XG Boost, DT-AdaBoost, and DT-Bagging. In addition to that, the performance model is also evaluated by using R2, root mean square error (RMSE), and mean absolute error (MAE). Furthermore, the k-fold cross-validation method is also applied to validate the model’s performance. It is observed that DT-Bagging with an R2 value of 0.95 is superior to DT-XG Boost, DT-Gradient Boosting, and DT-AdaBoost. Lesser error MAE and RMSE and higher R2 values for the DT-Bagging model show the enhanced performance of the model compared to the other ensembled approaches. Considerable conservation of time, effort, and cost can be made by applying ML techniques to predict concrete properties. The evaluation of the outcome depicts that the estimated results of DT-Bagging are closer to the experimental results, indicating the accurate estimation of SFRC flexural strength. It is further revealed from the SHapley Additive exPlanations (SHAP) study that the volumetric content of steel fiber highly and positively influences the FS of SFRC. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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28 pages, 8686 KiB  
Article
Design Solutions for Slender Bars with Variable Cross-Sections to Increase the Critical Buckling Force
by Marius Florin Botis and Camelia Cerbu
Materials 2022, 15(17), 6094; https://doi.org/10.3390/ma15176094 - 02 Sep 2022
Cited by 1 | Viewed by 1205
Abstract
In large metal civil constructions (stadium roofs, bridges), slender bars can lose their stability under compression loading. There is a lack in the literature regarding design solutions and methods for increasing the critical buckling force of bars with variable cross-sections. The aim of [...] Read more.
In large metal civil constructions (stadium roofs, bridges), slender bars can lose their stability under compression loading. There is a lack in the literature regarding design solutions and methods for increasing the critical buckling force of bars with variable cross-sections. The aim of this research is to present a numerical model with finite elements used for a comparative analysis of increasing the critical force of stability loss in cases of (i) bars with stepwise variation in the cross-sections and (ii) bars with continuous variation in the moment of inertia along the bar axis (parabolic, sinusoidal, triangular, and trapezoidal variation). Considering the large-scale applications in civil engineering, bars that were pin-connected at one end and simple-supported at the other end were analyzed. Firstly, the analytical model was described to compute the critical buckling force for bars with stepwise variation in the cross-sections. Then, a finite element model for a slender bar and the assumptions considered were presented. The results were computed using the MATLAB program based on the numerical model proposed and were validated with the analytical model for stepwise variable cross-sections of the bars. The numerical model was adapted for bars with continuous variation in the moment of inertia along the bar axis. It was shown that, by trapezoidal variation in the second moment of inertia along the axis of a bar, i.e., as buckling occurred in the elastic field, the critical buckling force could be increased by 3.556 times compared to a bar with a constant section. It was shown that there was certain bar with stepwise variation in the cross-section for which the critical buckling force was approximately equal to the one obtained for the bar with sinusoidal variation in the moment of inertia (increased by 3.427 times compared to a bar with a constant section). Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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14 pages, 2857 KiB  
Article
The Impact of Microwave Drying on the Structure of Exemplary Soils—Insights Using X-ray Microtomography
by Łukasz Kaczmarek, Małgorzata Jastrzębska and Tomasz Wejrzanowski
Materials 2022, 15(17), 5891; https://doi.org/10.3390/ma15175891 - 26 Aug 2022
Cited by 1 | Viewed by 1385
Abstract
In the field of soil drying methods, rapid microwave heating is progressively replacing conventional techniques. Due to the specific heat transport caused by microwaves, the drying process can significantly modify soil structure, which, in turn, can influence mechanical and filtration characteristics. In this [...] Read more.
In the field of soil drying methods, rapid microwave heating is progressively replacing conventional techniques. Due to the specific heat transport caused by microwaves, the drying process can significantly modify soil structure, which, in turn, can influence mechanical and filtration characteristics. In this study, we compared structural changes of exemplary non-cohesive (medium quartz sand (MSa)) and cohesive soil (silty clay mainly composed of kaolinite (siCl)). The sample materials were subjected to three different drying methods: air-drying, conventional oven (CO) drying, and microwave oven (MO) drying (MO). Soil structure was studied using X-ray microtomography (XµCT) and described in detail by image analysis methods. The study showed that the analyzed types of heating had a negligible effect on the structure of the sands, but a significant impact in the case of silty clay. Such a phenomenon is discussed and explained in this paper. The study advances the testing of soils microwave drying in a geotechnical laboratory. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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20 pages, 6739 KiB  
Article
Predicting the Durability of Solid Fired Bricks Using NDT Electroacoustic Methods
by Vojtěch Bartoň, Richard Dvořák, Petr Cikrle and Jaroslav Šnédar
Materials 2022, 15(17), 5882; https://doi.org/10.3390/ma15175882 - 25 Aug 2022
Cited by 4 | Viewed by 1439
Abstract
Historical buildings and monuments are largely made of brickwork. These buildings form the historical and artistic character of cities, and how we look after them is a reflection of our society. When assessing ceramic products, great emphasis is placed on their mechanical properties, [...] Read more.
Historical buildings and monuments are largely made of brickwork. These buildings form the historical and artistic character of cities, and how we look after them is a reflection of our society. When assessing ceramic products, great emphasis is placed on their mechanical properties, whilst their durability is often neglected. However, the durability or resistance to weathering of masonry elements is just as important as their mechanical properties. Therefore, this work deals with predicting the durability of solid-fired bricks before they are used when reconstructing monuments and historical buildings. Durability prediction is assessed by identifying defects in the material’s internal structure. These faults may not be visible on the element’s surface and are difficult to detect. For this purpose, non-destructive electroacoustic methods, such as the resonant pulse method or the ultrasonic pulse method, were used. Based on an analysis of the initial and residual mechanical properties after freezing cycles, four durability classes of solid-fired bricks were determined. This work aimed to find a way to predict the durability (lifetime) of an anonymous solid-fired brick, expressed in terms of the number of freeze cycles the brick would last, based on non-destructive measurements. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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14 pages, 5639 KiB  
Article
Identification of Parameters and Fatigue Life Assessment of the Road Pavement Lower Construction Layers under Heavy Construction Traffic
by Piotr Mackiewicz and Bartłomiej Krawczyk
Materials 2022, 15(16), 5646; https://doi.org/10.3390/ma15165646 - 17 Aug 2022
Cited by 3 | Viewed by 979
Abstract
This article analyzes the results of testing the subgrade and the lower layers of the pavement structure with the light weight deflectometer at a load of 0.1 and 0.15 MPa. It is shown that, with layer systems with an equivalent layer modulus lower [...] Read more.
This article analyzes the results of testing the subgrade and the lower layers of the pavement structure with the light weight deflectometer at a load of 0.1 and 0.15 MPa. It is shown that, with layer systems with an equivalent layer modulus lower than 80 MPa, significant nonlinear phenomena occur at a load of 0.15 MPa. In this situation, the identification of a reliable replacement module, a commonly used test method, at a load of 0.1 MPa, is not appropriate—it significantly overestimates the value of the modules (even by 34%), which in turn translates into a significant overestimation of the fatigue life of the structure. In a situation where intensive exploitation of the lower layers of the pavement structure is planned before the final layer arrangement is made, it is required to apply test loads corresponding to the stress conditions occurring in these layers of the structure. Such a situation takes place under the influence of technological (construction) or temporary traffic (substitute, e.g., by-pass) during construction. In order to verify the above assumptions, numerical calculations (FEM) were carried out in the elastic model for layered structures with replacement modules determined in field tests. It was found that, especially in the case of low-bearing layer systems, it is necessary to use correction factors for modules determined with a dynamic plate at a load of 0.1 MPa. Taking into account the corrected values of the modules will allow to correctly determine the change in the durability of layers at the construction stage and in the subsequent operation of the final pavement structure. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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22 pages, 13939 KiB  
Article
An Experimental Investigation of the Mechanical Behavior and Particle Crushing Characteristic of Volcanic Soil
by Xiao-Yang Liu, Chang-Ming Wang, Hai-Liang Liu and Di Wu
Materials 2022, 15(15), 5423; https://doi.org/10.3390/ma15155423 - 06 Aug 2022
Cited by 2 | Viewed by 1799
Abstract
Volcanic soil is a special soil that is well-known for its distinctive texture, vesicular nature, and particle fragility. The fragility characteristic of volcanic soil is the main factor affecting the foundation stability in road engineering. This study focuses on the mechanical properties and [...] Read more.
Volcanic soil is a special soil that is well-known for its distinctive texture, vesicular nature, and particle fragility. The fragility characteristic of volcanic soil is the main factor affecting the foundation stability in road engineering. This study focuses on the mechanical properties and particle crushing characteristics of volcanic soil retrieved from Northeast China. A series of triaxial consolidation and drainage shear tests are performed on volcanic coarse-grained soil (5 mm > d > 0.075 mm) under different initial relative densities and effective confining pressures. Results show the peak friction angle of volcanic soil significantly decreases with the increase of confining pressure. The particle crushing degree of volcanic soil increases with the increase of confining pressure, particle size, and relative density. The relative breakage rate of the same particle size group has a good linear relationship with a fractal dimension. Moreover, for the same particle size, the relationship between plastic work and relative breakage rate can be fitted by a power function, which is not significantly affected by relative density or effective confining pressure. From an engineering view, in addition to increasing the compaction degree of volcanic soil, volcanic soil with fine particles used as a roadbed filler can significantly reduce the deformation of the roadbed and improve the bearing capacity of the foundation. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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13 pages, 3914 KiB  
Article
Predicting the Rheological Properties of Super-Plasticized Concrete Using Modeling Techniques
by Muhammad Nasir Amin, Ayaz Ahmad, Kaffayatullah Khan, Waqas Ahmad, Saqib Ehsan and Anas Abdulalim Alabdullah
Materials 2022, 15(15), 5208; https://doi.org/10.3390/ma15155208 - 27 Jul 2022
Cited by 6 | Viewed by 1361
Abstract
Interface yield stress (YS) and plastic viscosity (PV) have a significant impact on the pumpability of concrete mixes. This study is based on the application of predictive machine learning (PML) techniques to forecast the rheological properties of fresh concrete. The artificial neural network [...] Read more.
Interface yield stress (YS) and plastic viscosity (PV) have a significant impact on the pumpability of concrete mixes. This study is based on the application of predictive machine learning (PML) techniques to forecast the rheological properties of fresh concrete. The artificial neural network (NN) and random forest (R-F) PML approaches were introduced to anticipate the PV and YS of concrete. In comparison, the R-F model outperforms the NN model by giving the coefficient of determination (R2) values equal to 0.92 and 0.96 for PV and YS, respectively. In contrast, the model’s legitimacy was also verified by applying statistical checks and a k-fold cross validation approach. The mean absolute error, mean square error, and root mean square error values for R-F models by investigating the YS were noted as 30.36 Pa, 1141.76 Pa, and 33.79 Pa, respectively. Similarly, for the PV, these values were noted as 3.52 Pa·s, 16.48 Pa·s, and 4.06 Pa·s, respectively. However, by comparing these values with the NN’s model, they were found to be higher, which also gives confirmation of R-F’s high precision in terms of predicting the outcomes. A validation approach known as k-fold cross validation was also introduced to authenticate the precision of employed models. Moreover, the influence of the input parameters was also investigated with regard to predictions of PV and YS. The proposed study will be beneficial for the researchers and construction industries in terms of saving time, effort, and cost of a project. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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19 pages, 9054 KiB  
Article
Effect of the Looseness of the Beam End Connection Used for the Pallet Racking Storage Systems, on the Mechanical Behavior of the Bearing Beams
by Florin Dumbrava and Camelia Cerbu
Materials 2022, 15(14), 4728; https://doi.org/10.3390/ma15144728 - 06 Jul 2022
Viewed by 1411
Abstract
The worldwide use of pallet racking storage systems leads to the necessity for research regarding the effects of the clearance between the metallic tabs of the connector and upright slots (looseness effect) on the performance of load-bearing beams. Firstly, the looseness angle and [...] Read more.
The worldwide use of pallet racking storage systems leads to the necessity for research regarding the effects of the clearance between the metallic tabs of the connector and upright slots (looseness effect) on the performance of load-bearing beams. Firstly, the looseness angle and the rotational stiffness were experimentally obtained for three types of beam-to-upright connections. A theoretical approach is used to investigate the magnitude of the looseness effects that occurred on the performances of the bearing beam of the pallet storage systems in terms of the bending moment developed at the midpoint of the beam and maximum deflection. Calculation corrections were evaluated for the connections involved in the experimental part, for the case which considers the looseness effects with respect to the case which does not consider the looseness effect. In order to evaluate the effects of the parameters of the connections on calculus corrections, the theoretical model was used for other types of beam-to-upright connections. It is shown that the maximum corrections are 2.99% and 5.16% for the bending moment developed at the midpoint of the beam and for the maximum deflection, respectively. It is proved that the connector type affects the size of the correction. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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22 pages, 4963 KiB  
Article
Both Plasticizing and Air-Entraining Effect on Cement-Based Material Porosity and Durability
by Aigerim Tolegenova, Gintautas Skripkiunas, Lyudmyla Rishko and Kenzhebek Akmalaiuly
Materials 2022, 15(13), 4382; https://doi.org/10.3390/ma15134382 - 21 Jun 2022
Cited by 4 | Viewed by 1492
Abstract
The influence of a complex application of both plasticizing and air-entraining effects on concrete with polycarboxylate ether superplasticizer (PCE), air-entraining admixture (AIR), or an anti-foaming agent (AF) is analyzed in this paper with considerations for on the air content, workability, flexural and compressive [...] Read more.
The influence of a complex application of both plasticizing and air-entraining effects on concrete with polycarboxylate ether superplasticizer (PCE), air-entraining admixture (AIR), or an anti-foaming agent (AF) is analyzed in this paper with considerations for on the air content, workability, flexural and compressive strength, and freezing–thawing resistance of hardened cement mixtures. The effect of the complex behavior of PCE, AIR, and AF on the porosity of hardened cement mortar (HCM) and freezing–thawing resistance was investigated; freezing–thawing resistance prediction methodology for plasticized mortar was also evaluated. The results presented in the article demonstrate the beneficial influence of entrained air content on consistency and stability of cement mortar, closed porosity, and durability of concrete. Freezing–thawing factor KF depending on porosity parameters can be used for freezing–thawing resistance prediction. With both plasticizing (decrease in the water–cement ratio) and air-entraining effects (increase in the amount of entrained air content), the frost resistance of concrete increases, scaling decreases exponentially, and it is possible to obtain great frost resistance for cement-based material. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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17 pages, 3248 KiB  
Article
Creation of a Nanomodified Backfill Based on the Waste from Enrichment of Water-Soluble Ores
by Elena A. Ermolovich, Alexander L. Ivannikov, Marat M. Khayrutdinov, Cheynesh B. Kongar-Syuryun and Yulia S. Tyulyaeva
Materials 2022, 15(10), 3689; https://doi.org/10.3390/ma15103689 - 21 May 2022
Cited by 38 | Viewed by 1792
Abstract
The paper analyzes losses during the development of low-value water-soluble ore deposits. The importance of development systems with backfill is shown. The use of industrial wastes of water-soluble ores to replace specially produced inert components in the preparation of backfill seems to be [...] Read more.
The paper analyzes losses during the development of low-value water-soluble ore deposits. The importance of development systems with backfill is shown. The use of industrial wastes of water-soluble ores to replace specially produced inert components in the preparation of backfill seems to be a good way to utilize them. The aim of the work was to create a fill mass with improved strength properties based on industrial wastes of water-soluble ores activated with a nanomodifying material. The characteristics (chemical and granulometric compositions) of an aggregate of the backfill based on the waste from enrichment of water-soluble ores are given. The validation of the hardening mixture compositions for various mining systems was carried out considering: the specified strength, the time of the artificial mass erection, the time to achieve the required strength properties of the material, which determine the possible intensity of the mining operations; method of transporting the backfill. The expediency of using a multilayer fulleroid nanomodifier astralene as a nanomodifying additive has been proved. The effect of the backfill activation with a nanomodifying additive, astralene, on the structural changes of halite wastes from the halurgic enrichment of water-soluble ores (potash) was investigated. To study the strength properties of the fill mass, the comparative analytical method was used. The strength properties of the backfill were measured in standard test periods, taking into account the intensity of hardening of the backfill material (after 7, 14, 28, 60, 90 days). To obtain reliable results, 10 backfill samples were tested at each of the scheduled dates. The shape and chemical composition of crystalline new forms were studied. Studies were performed using X-ray phase analysis and scanning electron microscopy. As a result of uniaxial compression of hardening backfill samples, the dependence of the ultimate strength on the astralene content and the hardening time were established. It has been experimentally proved that the use of a nanomodifying additive, astralene, in the backfill allows an increase in the strength properties of the created artificial mass by 1.76–2.36 times while reducing binder consumption. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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17 pages, 5365 KiB  
Article
Determination of Prestress Losses in Existing Pre-Tensioned Structures Using Bayesian Approach
by Martin Moravčík and Jakub Kraľovanec
Materials 2022, 15(10), 3548; https://doi.org/10.3390/ma15103548 - 16 May 2022
Cited by 4 | Viewed by 1325
Abstract
Deterioration of materials and structures is an unavoidable fact, and prestressed concrete structures are not an exception. The evaluation of load-carrying capacity and remaining service life includes collecting various information. However, one type of information is essential and the most important, the state [...] Read more.
Deterioration of materials and structures is an unavoidable fact, and prestressed concrete structures are not an exception. The evaluation of load-carrying capacity and remaining service life includes collecting various information. However, one type of information is essential and the most important, the state of prestressing, which inevitably decreases over time. Currently, many possible methods for the evaluation of prestressing are available. These techniques are part of the structural assessment and provide residual prestressing force value which is later used in the evaluation process. Therefore, it is suitable to provide the value of prestressing force based on certain probabilistic backgrounds. This study addresses the determination of residual prestressing force in pre-tensioned railway sleepers one year after their production, using the so-called Bayesian approach. This technique is focused on the validation of results obtained from the application of the non-destructive indirect saw-cut method. The Bayesian approach considers analytic calculation as the primary method of prestressing determination. In this paper, Monte Carlo simulation was used to determine the total variability that defines all Bayesian systems of probability functions. Specifically, a total of 1000 simulations was applied, and the current random vector of prestressing force derived from the analytical calculation has been assumed as a normally distributed function. Finally, obtained results for different depths of saw-cuts are compared. The results of the experimental and statistical determination of residual prestressing force provide its value with a 95% confidence level. This study suggests that the implementation of the probability approach can be an effective tool for determining prestress losses. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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13 pages, 2461 KiB  
Article
Assessment of the Destruction of a Fibre Cement Board Subjected to Fire in a Large-Scale Study
by Krzysztof Schabowicz, Paweł Sulik, Tomasz Gorzelańczyk and Łukasz Zawiślak
Materials 2022, 15(8), 2929; https://doi.org/10.3390/ma15082929 - 17 Apr 2022
Cited by 2 | Viewed by 2204
Abstract
This article presents the results of a study involving the assessment of the structural destruction of fibre cement boards taken from a large-scale model subjected to fire. These were subjected to a three-point bending test using the acoustic emission method. The analysis of [...] Read more.
This article presents the results of a study involving the assessment of the structural destruction of fibre cement boards taken from a large-scale model subjected to fire. These were subjected to a three-point bending test using the acoustic emission method. The analysis of the obtained results took into account the course of bending stresses σm, the modulus of rupture (MOR), the number of acoustic emission events Nzd and the sum of EA events ∑Nzd. The conducted tests showed that the samples subjected to fire exhibited a clear decrease, up to 72%, in the recorded sum of EA events compared to a reference board (not subjected to fire). The analysis of the obtained modulus of rupture (MOR) values showed a similar trend—the reduction of the modulus of rupture for the degraded samples was in the range of 66–96%. In order to illustrate the changes taking place in the structure of the tested plates more precisely, analyses were carried out using the optical method and a digital microscope. This method may be sufficient for the final evaluation of degraded samples. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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25 pages, 6051 KiB  
Article
Machine Learning Prediction Models to Evaluate the Strength of Recycled Aggregate Concrete
by Xiongzhou Yuan, Yuze Tian, Waqas Ahmad, Ayaz Ahmad, Kseniia Iurevna Usanova, Abdeliazim Mustafa Mohamed and Rana Khallaf
Materials 2022, 15(8), 2823; https://doi.org/10.3390/ma15082823 - 12 Apr 2022
Cited by 53 | Viewed by 3413
Abstract
Compressive and flexural strength are the crucial properties of a material. The strength of recycled aggregate concrete (RAC) is comparatively lower than that of natural aggregate concrete. Several factors, including the recycled aggregate replacement ratio, parent concrete strength, water–cement ratio, water absorption, density [...] Read more.
Compressive and flexural strength are the crucial properties of a material. The strength of recycled aggregate concrete (RAC) is comparatively lower than that of natural aggregate concrete. Several factors, including the recycled aggregate replacement ratio, parent concrete strength, water–cement ratio, water absorption, density of the recycled aggregate, etc., affect the RAC’s strength. Several studies have been performed to study the impact of these factors individually. However, it is challenging to examine their combined impact on the strength of RAC through experimental investigations. Experimental studies involve casting, curing, and testing samples, for which substantial effort, price, and time are needed. For rapid and cost-effective research, it is critical to apply new methods to the stated purpose. In this research, the compressive and flexural strengths of RAC were predicted using ensemble machine learning methods, including gradient boosting and random forest. Twelve input factors were used in the dataset, and their influence on the strength of RAC was analyzed. The models were validated and compared using correlation coefficients (R2), variance between predicted and experimental results, statistical tests, and k-fold analysis. The random forest approach outperformed gradient boosting in anticipating the strength of RAC, with an R2 of 0.91 and 0.86 for compressive and flexural strength, respectively. The models’ decreased error values, such as mean absolute error (MAE) and root-mean-square error (RMSE), confirmed the higher precision of the random forest models. The MAE values for the random forest models were 4.19 MPa and 0.56 MPa, whereas the MAE values for the gradient boosting models were 4.78 MPa and 0.64 MPa, for compressive and flexural strengths, respectively. Machine learning technologies will benefit the construction sector by facilitating the evaluation of material properties in a quick and cost-effective manner. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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14 pages, 4063 KiB  
Article
Modelling of Longitudinal Elastic Wave Propagation in a Steel Rod Using the Discrete Element Method
by Magdalena Knak, Michał Nitka, Erwin Wojtczak and Magdalena Rucka
Materials 2022, 15(8), 2738; https://doi.org/10.3390/ma15082738 - 08 Apr 2022
Cited by 1 | Viewed by 1556
Abstract
The paper deals with the issue of modelling elastic wave propagation using the discrete element method (DEM). The case of a longitudinal wave in a rod with a circular cross-section was considered. A novel, complex algorithm consisting of the preparation of models and [...] Read more.
The paper deals with the issue of modelling elastic wave propagation using the discrete element method (DEM). The case of a longitudinal wave in a rod with a circular cross-section was considered. A novel, complex algorithm consisting of the preparation of models and simulation of elastic waves was developed. A series of DEM models were prepared for simulations, differing in discretisation and material parameters. Additional calculations with the finite element method (FEM) were performed. Numerical wave signals were obtained from each simulation and compared with experimental results to choose the best DEM model based on the correlation between the waveforms. Moreover, dispersion curves were prepared for each model to verify the agreement with the Pochhammer-Chree wave propagation theory. Both experimental and theoretical approaches indicated the same model as the most suitable. The analysis results allowed stating that DEM can be successfully used for modelling wave propagation in structural rods. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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18 pages, 3861 KiB  
Article
Change in the Torsional Stiffness of Rectangular Profiles under Bending Stress
by Krzysztof Macikowski, Bogdan Warda, Grzegorz Mitukiewicz, Zlatina Dimitrova and Damian Batory
Materials 2022, 15(7), 2567; https://doi.org/10.3390/ma15072567 - 31 Mar 2022
Viewed by 1559
Abstract
This article presents the results of research on the change in torsional stiffness of two rectangular profiles, arranged one on top of the other, which were permanently connected at their ends. The flat bars were expanded in the middle of their active length. [...] Read more.
This article presents the results of research on the change in torsional stiffness of two rectangular profiles, arranged one on top of the other, which were permanently connected at their ends. The flat bars were expanded in the middle of their active length. The test involved determining the increase in the stiffness of a twisted test set before and after expanding. The authors present an analysis of the structure load and compare the results of tests carried out using analytical (for selected cases), numerical and experimental methods, obtaining satisfactory compliance. The analytical calculations included the influence of limited deplanation in the areas of the profile’s restraint. The ANSYS package software was used for calculations with the Finite Element Method. A change in the stiffness increase index at torsion was determined. The obtained results showed that expanding the test sets in their middle causes an increase in torsional stiffness, which is strongly dependent on the design parameters such as bending deflection, torsion angle and dimensions of the cross-section of the flat bar in the package. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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15 pages, 4288 KiB  
Article
Application of X-ray Computed Tomography to Verify Bond Failures Mechanism of Fiber-Reinforced Fine-Grain Concrete
by Grzegorz Piotr Kaczmarczyk, Roman Kinasz, Vitaliy Bilozir and Ivanna Bidenko
Materials 2022, 15(6), 2193; https://doi.org/10.3390/ma15062193 - 16 Mar 2022
Cited by 5 | Viewed by 1856
Abstract
This paper proposes the use of X-ray computed tomography (µCT, xCT) measurements together with finite element method (FEM) numerical modelling to assess bond failures mechanism of fiber-reinforced fine-grain concrete. Fiber-reinforced concrete is becoming popular for application in civil engineering structures. A dynamically developing [...] Read more.
This paper proposes the use of X-ray computed tomography (µCT, xCT) measurements together with finite element method (FEM) numerical modelling to assess bond failures mechanism of fiber-reinforced fine-grain concrete. Fiber-reinforced concrete is becoming popular for application in civil engineering structures. A dynamically developing topic related to concretes is the determination of bond characteristics. Nowadays, modern technologies allow inspecting the inside of the element without the need to damage its structure. This paper discusses the application of computed tomography in order to identify damage occurring in the structure of fiber-reinforced fine-grain concrete during bond failure tests. The publication is part of a larger study to determine the bonding properties of Ukrainian steel fibers in fine-grain concrete. The authors focused on the visual evaluation of sections obtained from tomographic data. Separately, the results of volumetric analysis were presented to quantitatively assess the changes occurring in the matrix structure. Finite element analysis is an addition to the substantive part and allows us to compare real damage areas with theoretical stress concentration areas. The result of the work is the identification of a path that allows verification of the locations where matrix destruction occurs. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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19 pages, 4477 KiB  
Article
Reliability Assessment Approach for the Quality of Railroad Subgrade
by Janusz Vitalis Kozubal, Piotr Wyborski, Matylda Tankiewicz and Igor Gisterek
Materials 2022, 15(5), 1864; https://doi.org/10.3390/ma15051864 - 02 Mar 2022
Viewed by 2098
Abstract
The static load plate test is the standard subgrade acceptance test for new or modernised railway lines. Examinations are performed at regular spacings on the track section and a lack of acceptance for even a single test disqualifies a section, forcing remedial treatments [...] Read more.
The static load plate test is the standard subgrade acceptance test for new or modernised railway lines. Examinations are performed at regular spacings on the track section and a lack of acceptance for even a single test disqualifies a section, forcing remedial treatments on the whole section. In this paper, a nondeterministic description of stiffness related to the spatial characteristics of acceptance measurement results is proposed for a more rational assessment of substructure quality. The concept is based on geostatistical analysis and one-dimensional distributions of stiffness values. The paper also proposes a new concept of rail infrastructure acceptance based on a reliability index already codified in European standards. The functioning of the postulated criterion is presented on the example of an existing railway line and the actual test results. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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15 pages, 7474 KiB  
Article
Numerical Evaluation of the Hygrothermal Performance of a Capillary Active Internal Wall Insulation System under Different Internal Conditions
by Dobrosława Kaczorek
Materials 2022, 15(5), 1862; https://doi.org/10.3390/ma15051862 - 02 Mar 2022
Viewed by 1809
Abstract
In certain situations, internal insulation is the only possible renovation option. However, it is risky where there is high humidity in a building and ventilation is not working sufficiently. The internal insulation retrofit changes the original thermal and moisture balance of a wall, [...] Read more.
In certain situations, internal insulation is the only possible renovation option. However, it is risky where there is high humidity in a building and ventilation is not working sufficiently. The internal insulation retrofit changes the original thermal and moisture balance of a wall, therefore, it is necessary to carefully design it already at the initial stage. This paper analyses four interior insulation systems based on open diffusion capillary active materials: wood fibreboards (flex and rigid), perlite boards, and microporous calcium silicate. The hygrothermal performance under the climatic conditions of Central Europe (Poland) was assessed using the WUFI Plus software, taking into account the dynamic variation of indoor and outdoor conditions. The analysis included three insulation thicknesses with different ventilation rates and varying moisture loads. The results show that the hygrothermal properties of the wall change with the increase of insulation thickness and depend on the individual moisture properties of the material. In addition, both the reduction of moisture load and more intensive air exchange improve the hygrothermal properties at the interface between the insulation and the wall. Of all the solutions analysed, the system with perlite board and the system with wood fibreboard showed the worst hygric properties. Conversely, the highest risk of mould and interstitial condensation was recorded for the flex wood fibreboard solution. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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17 pages, 6966 KiB  
Article
Damage Identification Method for Medium- and Small-Span Bridges Based on Macro-Strain Data under Vehicle–Bridge Coupling
by Hao Zhang, Zhixin Zhong, Junmiao Duan, Jianke Yang, Zhichao Zheng and Guangxun Liu
Materials 2022, 15(3), 1097; https://doi.org/10.3390/ma15031097 - 30 Jan 2022
Cited by 5 | Viewed by 2164
Abstract
The damage identification method based on macro-strain modality has shown good results for large-span flexible bridges. However, medium- and small-span bridges have a high stiffness, and the axle system is embodied. The strong time-varying vibration characteristics, coupled with the non-stationary characteristics of vehicle [...] Read more.
The damage identification method based on macro-strain modality has shown good results for large-span flexible bridges. However, medium- and small-span bridges have a high stiffness, and the axle system is embodied. The strong time-varying vibration characteristics, coupled with the non-stationary characteristics of vehicle loads, make it difficult to accurately determine the stable strain modes of such bridges. To solve this problem, a damage localization index in the form of an amplitude vector matrix of the mutual energy density spectrum based on macro-strain was constructed using wavelet transform de-noising and reconstruction technology and cross-correlation function. The macro-static strain and macro-dynamic strain data obtained from a vehicle–bridge coupling experiment were reconstructed through wavelet transform, and the factors influencing the damage indices were analyzed. The results showed that the proposed indicators could help realize an accurate damage localization for medium- and small-span bridge systems with different damage degrees under the action of vehicle–bridge coupling. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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15 pages, 5410 KiB  
Article
Mechanism and Performance of Bituminous Mixture Using 100% Content RAP with Bio-Rejuvenated Additive (BRA)
by Anqi Chen, Yazhen Qiu, Xiangyu Wang, Yuanyuan Li, Shaopeng Wu, Quantao Liu, Fan Wu, Jianlin Feng and Zhuowei Lin
Materials 2022, 15(3), 723; https://doi.org/10.3390/ma15030723 - 18 Jan 2022
Cited by 14 | Viewed by 1743
Abstract
The low RAP content, hot mixing conditions, and the addition of a high ratio of new bitumen and aggregates result in low economic and environmental benefits for current regeneration technologies. A bio-rejuvenated additive (BRA) that can fully (100%) regenerate the RAP without heating [...] Read more.
The low RAP content, hot mixing conditions, and the addition of a high ratio of new bitumen and aggregates result in low economic and environmental benefits for current regeneration technologies. A bio-rejuvenated additive (BRA) that can fully (100%) regenerate the RAP without heating is proposed in this paper. To reveal the mechanisms of BRA-rejuvenated RAP, the effects of BRA on the chemical structure and molecular weight of the RAP were investigated using Fourier-transform infrared spectroscopy and gel permeation chromatography. The mechanical performance and water damage resistance of BRA-rejuvenated RAP were studied. Low contents of new bitumen or epoxy resin were suggested to increase the mechanical performance of 100% RAP. The results show that the 1.5% BRA-rejuvenated RAP had the best mechanical performance. The blending of BRA with recycled RAP is a completely physical process, without any chemical reactions. The molecular weight of BRA is lower than that of bitumen; it can substantially increase the content of light components in aged bitumen, and play the role of adjusting and restoring the balance of the components of aged bitumen. The mechanical performance of BRA-rejuvenated RAP is enhanced significantly by adding low dosages of new bitumen or epoxy resin. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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16 pages, 3670 KiB  
Article
Effects of Low-Temperature Construction Additives (LCAs) on the Performance of Asphalt Mixtures
by Yuanyuan Li, Jianlin Feng, Anqi Chen, Fan Wu, Shaopeng Wu, Quantao Liu and Ruifang Gong
Materials 2022, 15(2), 677; https://doi.org/10.3390/ma15020677 - 17 Jan 2022
Cited by 4 | Viewed by 1688
Abstract
Green production of asphalt materials is very important to promote energy savings and emission reduction during the construction and maintenance of asphalt pavement. A low-temperature construction additive (LCA) made from the waste plastic and waste rubber is proposed, which belongs to a class [...] Read more.
Green production of asphalt materials is very important to promote energy savings and emission reduction during the construction and maintenance of asphalt pavement. A low-temperature construction additive (LCA) made from the waste plastic and waste rubber is proposed, which belongs to a class of environmentally friendly additives for asphalt mixtures. Marshall stability was tested to evaluate the mechanical performance of LCA-modified asphalt mixtures (LCA-AMs). In order to determine the best preparation parameters of LCA-AMs, the influence of the content and LCA addition method on the strength of LCA-AMs was studied. In addition, the impact of epoxy resin (ER) on the mixtures’ performances was evaluated. The results show that the LCA can significantly reduce the formation temperature of asphalt mixtures, and the resulting asphalt mixtures have good workability in a lower temperature range (90–110 °C). The ER should be added to the LCA-AMs after 4 h of curing. All the volumetric properties satisfy the technical requirements. The low-temperature crack resistance and fatigue resistance of LCA-AMs were obviously improved with appropriate dosages of ER, which can effectively improve the mechanical performance of the asphalt mixtures. The ER can significantly increase the rutting resistance and water sensitivity of LCA-AMs, therefore making it feasible to improve the mixture performance by the enhancement provided by a low dosage of ER. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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19 pages, 19094 KiB  
Article
Research and TLS (LiDAR) Construction Diagnostics of Clay Brick Masonry Arched Stairs
by Rafał Nowak, Tomasz Kania, Radosław Rutkowski and Ewa Ekiert
Materials 2022, 15(2), 552; https://doi.org/10.3390/ma15020552 - 12 Jan 2022
Cited by 10 | Viewed by 2019
Abstract
The study presents the terrestrial laser scanning (TLS) diagnostic of the clay brick masonry arched staircase in a historic building. Based on the measurements of the existing arched stair flights, 1:1 scale experimental models with and without stair treads were made. Strength tests [...] Read more.
The study presents the terrestrial laser scanning (TLS) diagnostic of the clay brick masonry arched staircase in a historic building. Based on the measurements of the existing arched stair flights, 1:1 scale experimental models with and without stair treads were made. Strength tests of the models were carried out for different concentrated force locations in relation to the supporting structure. Force, deflections and reaction in the upper support of the run were measured during the tests. The influence of the masonry steps on the curved vault on the load capacity and stiffness of the run structure was analyzed. The conducted experimental investigations showed that the key element responsible for the actual load-bearing capacity and stiffness of this type of stair flights were the treads above the masonry arch. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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20 pages, 7596 KiB  
Article
Artificial Weathering Resistance Test Methods for Building Performance Assessment of Profiles Made of Natural Fibre-Reinforced Polymer Composites
by Ewa Sudoł, Ewelina Kozikowska and Ewa Szewczak
Materials 2022, 15(1), 296; https://doi.org/10.3390/ma15010296 - 31 Dec 2021
Cited by 2 | Viewed by 1944
Abstract
A growing popularity of profiles made of natural fibre-reinforced polymer composites in civil engineering encourages determining test methods relevant for building performance assessment. Weathering resistance is among the key aspects that condition the durability of building structures. The paper includes a comparative analysis [...] Read more.
A growing popularity of profiles made of natural fibre-reinforced polymer composites in civil engineering encourages determining test methods relevant for building performance assessment. Weathering resistance is among the key aspects that condition the durability of building structures. The paper includes a comparative analysis of two artificial weathering resistance test methods. Polyvinyl chloride and wood flour composite profiles were tested. They were subjected to UV and spraying (X-exposure) and UV, spraying and wetting by condensation (F-exposure), both at different exposure times. The influence of the applied weathering procedures on the composite’s microstructure and its mechanical characteristics were analysed. No changes in the microstructure of brittle fractures were observed. However, surface morphology changes were revealed, noticeably greater following X-exposure than F-exposure. F-exposure exerted significant influence on the mechanical properties of brushed profile, including, but not limited to, flexural modulus. Whereas X-exposure exerted more influence on the mechanical properties of non-brushed profile. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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14 pages, 7794 KiB  
Article
Interlaboratory Comparison as a Source of Information for the Product Evaluation Process. Case Study of Ceramic Tiles Adhesives
by Cristina Stancu and Jacek Michalak
Materials 2022, 15(1), 253; https://doi.org/10.3390/ma15010253 - 29 Dec 2021
Cited by 6 | Viewed by 1527
Abstract
In this study, the results obtained by 19 laboratories participating in 2 editions of the interlaboratory comparison (ILC) determining 2 properties of ceramic tiles adhesives (CTAs), i.e., initial tensile adhesion strength and tensile adhesion strength after water immersion following EN 12004, were analyzed. [...] Read more.
In this study, the results obtained by 19 laboratories participating in 2 editions of the interlaboratory comparison (ILC) determining 2 properties of ceramic tiles adhesives (CTAs), i.e., initial tensile adhesion strength and tensile adhesion strength after water immersion following EN 12004, were analyzed. The results show that participating laboratories maintain a constant quality of their work. The use of z-score analysis, under ISO 13528, allows for classifying 89.5% to 100% of laboratories as satisfactory, depending on the measurement’s kind and edition. The remaining laboratories are classified as questionable. The investigation of the predominant mode of failure of the CTA’s samples tested in the two editions shows significant differences. From the perspective of laboratories, the goal of the ILC has been achieved. From the standpoint of a manufacturer who evaluates a product’s properties when placing it on the market, the results indicate the necessity of a particular treatment of the product evaluation process because the variability of the obtained results is significant. It increases the possibility of the product failing to meet the assessment criteria verified by the construction market supervision authorities. The manufacturer must consider all possible variations in the risk analysis, including the ILC results, to improve the assessment process of CTAs. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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23 pages, 7025 KiB  
Article
Prediction of Bending, Buckling and Free-Vibration Behaviors of 3D Textile Composite Plates by Using VAM-Based Equivalent Model
by Senbiao Xi, Yifeng Zhong, Zheng Shi and Qingshan Yi
Materials 2022, 15(1), 134; https://doi.org/10.3390/ma15010134 - 24 Dec 2021
Cited by 2 | Viewed by 1887
Abstract
To solve the microstructure-related complexity of a three-dimensional textile composite, a novel equivalent model was established based on the variational asymptotic method. The constitutive modeling of 3D unit cell within the plate was performed to obtain the equivalent stiffness, which can be inputted [...] Read more.
To solve the microstructure-related complexity of a three-dimensional textile composite, a novel equivalent model was established based on the variational asymptotic method. The constitutive modeling of 3D unit cell within the plate was performed to obtain the equivalent stiffness, which can be inputted into the 2D equivalent model (2D-EPM) to perform the bending, free-vibration and buckling analysis. The correctness and effectiveness of the 2D-EPM was validated by comparing with the results from 3D FE model (3D-FEM) under various conditions. The influence of yarn width and spacing on the equivalent stiffness was also discussed. Finally, the effective performances of 3D textile composite plate and 2D plain-woven laminate with the same thickness and yarn content were compared. The results revealed that the bending, buckling and free-vibration behaviors predicted by 2D-EPM were in good agreement with 3D-FEM, and the local field distributions within the unit cell of 3D textile composite plate were well captured. Compared with the 2D plain-woven laminate, the displacement of 3D textile composite plate was relatively larger under the uniform load, which may due to the fact that the through-the-thickness constrains of the former are only dependent on the binder yarns, while the warp yarns and weft yarns of the latter are intertwined closely. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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27 pages, 6014 KiB  
Article
Non-Destructive Possibilities of Thermal Performance Evaluation of the External Walls
by Henryk Nowak and Łukasz Nowak
Materials 2021, 14(23), 7438; https://doi.org/10.3390/ma14237438 - 04 Dec 2021
Cited by 3 | Viewed by 1394
Abstract
Identification of the actual thermal properties of the partitions of building enclosures has a significant meaning in determining the actual energy consumption in buildings and in their thermal comfort parameters. In this context, the total thermal resistance of the exterior walls (and therefore [...] Read more.
Identification of the actual thermal properties of the partitions of building enclosures has a significant meaning in determining the actual energy consumption in buildings and in their thermal comfort parameters. In this context, the total thermal resistance of the exterior walls (and therefore their thermal transmittance) in the building is a major factor which influences its heat losses. There are many methods to determine the total thermal resistance of existing walls, including the quantitative thermography method (also used in this study). This paper presents a comparison of the calculated total thermal resistance values and the measured ones for three kinds of masonry walls without thermal insulation and the same walls insulated with expanded polystyrene boards. The measurements were carried out in quasi-stationary conditions in climate chambers. The following three test methods were used: the temperature-based method (TBM), the heat flow meter method (HFM) and the infrared thermography method (ITM). The measurement results have been found to be in good agreement with the theoretically calculated values: 61% of the measured values were within 10% difference from the mean value of total thermal resistance for a given external wall and 79% of the results were within 20% difference. All of the used measuring methods (TBM, HFM and ITM) have proven to be similarly approximate in obtained total thermal resistances, on average between 6% and 11% difference from the mean values. It has also been noted that, while performing measurements, close attention should be paid to certain aspects, because they can have a major influence on the quality of the result. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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18 pages, 3324 KiB  
Article
Study of the Interfacial Bond Behavior between CFRP Grid–PCM Reinforcing Layer and Concrete via a Simplified Mechanical Model
by Huijuan Dai, Bo Wang, Jiawei Zhang, Junlei Zhang and Kimitaka Uji
Materials 2021, 14(22), 7053; https://doi.org/10.3390/ma14227053 - 20 Nov 2021
Cited by 1 | Viewed by 1656
Abstract
This paper presents the results of pull-out tests conducted to investigate the interfacial bond behavior between a carbon-fiber-reinforced polymer (CFRP) grid–polymer cement mortar (PCM) reinforcing layer and existing concrete, and proposes a simplified mechanical model to further study the interface bond mechanism. Four [...] Read more.
This paper presents the results of pull-out tests conducted to investigate the interfacial bond behavior between a carbon-fiber-reinforced polymer (CFRP) grid–polymer cement mortar (PCM) reinforcing layer and existing concrete, and proposes a simplified mechanical model to further study the interface bond mechanism. Four specimens composed of a CFRP grid, PCM, and concrete were tested. The influence of the type of CFRP grid and the grid interval on the interface bond behavior was discussed. The failure patterns, maximum tensile loads, and CFRP grid strains were obtained. The change process of interface bond stress was investigated based on the grid strain analysis. In addition, the simplified mechanical model and finite element model (FEM) were emphatically established, and the adaptability of the simplified mechanical model was validated through the comparative analysis between the FEM results and the test results. The research results indicate that a CFRP grid with a larger cross-sectional area and smaller grid interval could effectively improve the interface bond behavior. The tensile stress was gradually transferred from the loaded edge to the free edge in the CFRP grid. The interface bond behavior was mainly dependent on the anchorage action of the CFRP grid in the PCM, and the bond action between the PCM and the concrete. The FEM results were consistent with the test results, and the simplified mechanical model with nonlinear springs could well describe the interface bond mechanism between the CFRP grid–PCM reinforcing layer and concrete. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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20 pages, 23881 KiB  
Article
Experimental Study on the Axial Compression Performance of an Underwater Concrete Pier Strengthened by Self-Stressed Anti-Washout Concrete and Segments
by Shaofeng Wu, Yijun Ge, Shaofei Jiang, Sheng Shen and Heng Zhang
Materials 2021, 14(21), 6567; https://doi.org/10.3390/ma14216567 - 01 Nov 2021
Cited by 2 | Viewed by 1283
Abstract
Compared with the conventional drainage strengthening techniques, the precast concrete segment assembly strengthening method (PCSAM) is regarded as a fast, more economical, and traffic-friendly underwater strengthening method for damaged bridge piers and piles, as the drainage procedure can be omitted. However, this method [...] Read more.
Compared with the conventional drainage strengthening techniques, the precast concrete segment assembly strengthening method (PCSAM) is regarded as a fast, more economical, and traffic-friendly underwater strengthening method for damaged bridge piers and piles, as the drainage procedure can be omitted. However, this method still has some disadvantages, such as strength loss of the filling material, debonding of the interface due to shrinkage of the filling material, poor connection effects, and poor durability of the segment sleeves. To solve these problems, the PCSAM is improved in this study by using self-stressed anti-washout concrete (SSAWC) as the filling material and by developing a lining concrete segment sleeve (LCSS) by referring to the design theory for shield lining segments. Six specimens are designed and prepared with consideration of the influential factors, such as the self-stress, thickness of the filled concrete, and concrete strength of the LCSS, then the monotonic axial compression test is carried out to investigate the improvements in the axial compression properties of the specimens. Accordingly, extended parametric analyses are performed based on the established numerical models. Finally, the calculation formula for the bearing capacity is proposed based on the analysis results. The results indicate that the SSAWC can provide initial confining compressive stress in the core region of the piers, in addition to increasing the bearing capacity and ductility of the specimens. The improved LCSS segment connection is more reliable and increases the strengthening efficiency. The influence of self-stress on the bearing capacity of the specimens is cubic and the influence of the filled concrete strength on the bearing capacity of the specimens is nonlinear. The calculation formula for predicting the bearing capacity of axially compressed columns possesses good applicability and can be used as a reference for practical engineering. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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18 pages, 6327 KiB  
Article
Strength Parameters of Clay Brick Walls with Various Directions of Force
by Rafał Nowak, Tomasz Kania, Valery Derkach, Romuald Orłowicz, Anton Halaliuk, Ewa Ekiert and Rafał Jaworski
Materials 2021, 14(21), 6461; https://doi.org/10.3390/ma14216461 - 28 Oct 2021
Cited by 5 | Viewed by 2172
Abstract
The study analyzes the anisotropy effect for ceramic masonry based on experimental tests of samples made of 25 × 12 × 6.5 cm3 solid brick elements with compressive strength fb = 44.1 MPa and cement mortar with compressive strength fm [...] Read more.
The study analyzes the anisotropy effect for ceramic masonry based on experimental tests of samples made of 25 × 12 × 6.5 cm3 solid brick elements with compressive strength fb = 44.1 MPa and cement mortar with compressive strength fm = 10.9 MPa. The samples were loaded in a single plane with a joint angle that varied from the horizontal plane. The load was applied in a vertical direction. The samples were loaded at angles of 90°, 67.5°, 45°, 22.5°, and 0° toward the bed joints. The most unfavourable cases were determined. It was observed that the anisotropy of the masonry significantly influences the load-bearing capacity of the walls depending on the angle of the compressive stresses trajectory. Approximation curves and equations for compressive strength, Young’s modulus, and Poisson’s coefficient were proposed. It was observed that Young’s modulus and Poisson’s ratio will also change depending on the trajectory of compressive stresses as a function of the joint angle. Experimental tests allowed to determine the failure mechanism in prepared specimens. The study allowed to estimate the masonry strength with the load acting at different angles toward the bed joints. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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15 pages, 4622 KiB  
Article
Effective Length Prediction and Pullout Design of Geosynthetic Strips Based on Pullout Resistance
by Jeongjun Park and Gigwon Hong
Materials 2021, 14(20), 6151; https://doi.org/10.3390/ma14206151 - 16 Oct 2021
Cited by 4 | Viewed by 1414
Abstract
In this study, pullout tests were conducted on geosynthetic strips which can be applied to a block-type front wall. Based on the test results, the effective length is predicted, and the pullout design results are presented. In other words, the pullout displacement–pullout load [...] Read more.
In this study, pullout tests were conducted on geosynthetic strips which can be applied to a block-type front wall. Based on the test results, the effective length is predicted, and the pullout design results are presented. In other words, the pullout displacement–pullout load relationship of all geosynthetic strips was analyzed using the pullout test results, and their effective lengths were predicted. It was found that the reinforcement width affected the pullout force for the geosynthetic strips at the same tensile strength. The pullout behavior was evidenced within a range of approximately 0.45 L of the total length of the reinforcement (L) and hardly occurred beyond a certain distance from the geosynthetic strips front regardless of the normal stress. Based on these pullout behavioral characteristics, a method is proposed for the prediction of the effective length (LE) and maximum effective length (LE(max)) of a geosynthetic strip. The pullout strength was compared using the total area and effective area methods in accordance with the proposed method. In the case of the total area method, GS50W (width: 50 mm) and GS70W (width: 70 mm) exhibited similar pullout strengths. The pullout strength by the effective area method, however, was found to be affected by the soil-reinforcement interface adhesion. The proposed method used for the prediction of the effective length of a geosynthetic strip was evaluated using a design case. It was confirmed that the method achieved an economical design in instances in which the pullout resistance by the effective length (LE) was applied compared with the existing method. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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17 pages, 30836 KiB  
Article
Analysis of the Frequency of Acoustic Emission Events in Terms of the Assessment of the Reduction of Mechanical Parameters of Cellulose–Cement Composites
by Anna Adamczak-Bugno, Aleksandra Krampikowska and Grzegorz Świt
Materials 2021, 14(19), 5882; https://doi.org/10.3390/ma14195882 - 08 Oct 2021
Cited by 2 | Viewed by 1586
Abstract
The article proposes the application of the acoustic emission method as a technique for the evaluation of mechanical parameters of cellulose–cement composites. The analysis focused on frequency values in a time series analysis of elements subject to three-point flexural stress. In the course [...] Read more.
The article proposes the application of the acoustic emission method as a technique for the evaluation of mechanical parameters of cellulose–cement composites. The analysis focused on frequency values in a time series analysis of elements subject to three-point flexural stress. In the course of a statistic analysis, it has been demonstrated that a significant reduction of the recorded frequency values is associated with a considerable reduction in strength. This allowed the authors to determine the range of frequencies related to the depreciation in the strength of an element. The tests were carried out on elements cut from a full-size cellulose–cement board. Samples exposed to potential operational factors (environmental and exceptional) were analysed. It was shown that the frequencies recorded before reaching the maximum load during bending of samples exposed to environmental factors (water and low temperature) were significantly different (were much lower) from the sounds emitted by elements subjected to exceptional factors (fire and high temperature). Considering the fact that the analysed frequencies of acoustic emission events occur before the maximum stresses in the material are reached and the elements are destroyed, this provides the basis for the use of the acoustic emission method to assess the condition of cellulose–cement composites in terms of lowering mechanical parameters by observing the frequency of events generated by the material during load action. It was found that generating by material frequencies above 300 kHz during bending does not result in a significant decrease in mechanical parameters. The emission of signals with frequencies ranging from 200 to 300 kHz indicate that there was a decline in strength exceeding 25% but less than 50%. The registration of signals with frequencies below 200 kHz indicates that the reduction in mechanical parameters was greater than 50%. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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13 pages, 2159 KiB  
Article
Fatigue Resistance and Cracking Mechanism of Semi-Flexible Pavement Mixture
by Shiqi Wang, Huanyun Zhou, Xianhua Chen, Minghui Gong, Jinxiang Hong and Xincheng Shi
Materials 2021, 14(18), 5277; https://doi.org/10.3390/ma14185277 - 14 Sep 2021
Cited by 16 | Viewed by 2229
Abstract
Semi-flexible pavement (SFP) is widely used in recent years because of its good rutting resistance, but it is easy to crack under traffic loads. A large number of studies are aimed at improving its crack resistance. However, the understanding of its fatigue resistance [...] Read more.
Semi-flexible pavement (SFP) is widely used in recent years because of its good rutting resistance, but it is easy to crack under traffic loads. A large number of studies are aimed at improving its crack resistance. However, the understanding of its fatigue resistance and fatigue-cracking mechanism is limited. Therefore, the semi-circular bending (SCB) fatigue test is used to evaluate the fatigue resistance of the SFP mixture. SCB fatigue tests under different temperature values and stress ratio were used to characterize the fatigue life of the SFP mixture, and its laboratory fatigue prediction model was established. The distribution of various phases of the SFP mixture in the fracture surface was analyzed by digital image processing technology, and its fatigue cracking mechanism was analyzed. The results show that the SFP mixture has better fatigue resistance under low temperature and low stress ratio, while its fatigue resistance under other environmental and load conditions is worse than that of asphalt mixture. The main reason for the poor fatigue resistance of the SFP mixture is the poor deformation capacity and low strength of grouting materials. Furthermore, the performance difference between grouting material and the asphalt binder is large, which leads to the difference of fatigue cracking mechanism of the SFP mixture under different conditions. Under the fatigue load, the weak position of the SFP mixture at a low temperature is asphalt binder and its interface with other materials, while at medium and high temperatures, the weak position of the SFP mixture is inside the grouting material. The research provides a basis for the calculation of the service life of the SFP structure, provides a reference for the improvement direction of the SFP mixture composition and internal structure. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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16 pages, 4291 KiB  
Article
Factors Influencing the Load-Bearing Capacity of Rock as Base Material for Post-Installed Anchors
by Stefan Lamplmair, Oliver Zeman and Klaus Voit
Materials 2021, 14(18), 5130; https://doi.org/10.3390/ma14185130 - 07 Sep 2021
Cited by 4 | Viewed by 1417
Abstract
In the case of fastenings on rock, as a result of the variability, it is quite difficult to make a preliminary assessment of the load-bearing capacity of rock as a base material. This paper therefore investigates which rock parameters next to an anchor [...] Read more.
In the case of fastenings on rock, as a result of the variability, it is quite difficult to make a preliminary assessment of the load-bearing capacity of rock as a base material. This paper therefore investigates which rock parameters next to an anchor position have an influence on the load-bearing capacity. For this purpose, tests are carried out on post-installed anchors in different lithologies in eastern Austria. It can be shown that the joint weathering has an influence on the load-bearing capacity of post-installed anchors and conclusions can be made about joint weathering by means of rebound hammer. Rebound values can therefore also be used to draw conclusions about the rock quality as a base material for post-installed anchors. Nevertheless, a combined optical assessment of the base material is recommended as an adequate method. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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19 pages, 16846 KiB  
Article
Imaging of Increasing Damage in Steel Plates Using Lamb Waves and Ultrasound Computed Tomography
by Monika Zielińska and Magdalena Rucka
Materials 2021, 14(17), 5114; https://doi.org/10.3390/ma14175114 - 06 Sep 2021
Cited by 9 | Viewed by 2156
Abstract
This paper concerns the inspection of steel plates, with particular emphasis on the assessment of increasing damage. Non-destructive tests were performed on four plates, one of which was undamaged, while the remaining three had defects in the form of circular holes with diameters [...] Read more.
This paper concerns the inspection of steel plates, with particular emphasis on the assessment of increasing damage. Non-destructive tests were performed on four plates, one of which was undamaged, while the remaining three had defects in the form of circular holes with diameters of 2, 5 and 10 cm. Guided Lamb waves were used in the research, and the image reconstruction was performed using ultrasound computed tomography. The damage size was estimated by tracking the real course of rays and densifying the pixel grid into which the object was divided. The results showed the great potential of ultrasound tomography in detecting defects in steel elements, together with the possibility of estimating damage size. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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21 pages, 5596 KiB  
Article
Estimating of the Static and Dynamic Behaviors of Orthogrid-Stiffened FRP Panel Using Reduced-Order Plate Model
by Peng Wang, Yifeng Zhong, Zheng Shi, Dan Luo and Qingshan Yi
Materials 2021, 14(17), 4908; https://doi.org/10.3390/ma14174908 - 28 Aug 2021
Cited by 2 | Viewed by 1585
Abstract
The orthogrid-stiffened FRP panel (OSFP) is a generic structural element in weight-sensitive structure applications. Based on the variational asymptotic method, a 2D reduced-order plate model (2D-RPM) of OSFP was constructed through matching the strain energy of the original panel for static and dynamic [...] Read more.
The orthogrid-stiffened FRP panel (OSFP) is a generic structural element in weight-sensitive structure applications. Based on the variational asymptotic method, a 2D reduced-order plate model (2D-RPM) of OSFP was constructed through matching the strain energy of the original panel for static and dynamic analyses. The local field distributions were recovered using the recovery relationship and global response. The relative influences of select parameters on the effective performance of the OSFP were revealed by parametric studies. The comparative results showed that the effective performance of the OSFP predicted by the 2D-RPM were consistent with those predicted by the 3D finite element model, but the computational efficiency was greatly improved. The stiffener height had the greatest influence on the natural frequency of the panel. The layup configurations of laminates had significant influences on the equivalent stiffness and buckling load of the OSFP but had little effect on the vibration modes, which could be varied by adjusting the stiffening forms. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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0 pages, 4943 KiB  
Article
Numerical Analysis of Steel Geodesic Dome under Seismic Excitations
by Dominika Bysiec and Tomasz Maleska
Materials 2021, 14(16), 4493; https://doi.org/10.3390/ma14164493 - 10 Aug 2021
Cited by 26 | Viewed by 5184 | Correction
Abstract
The paper presents the response of two geodesic domes under seismic excitations. The structures subjected to seismic analysis were created by two different methods of subdividing spherical triangles (the original octahedron face), as proposed by Fuliński. These structures are characterised by the similar [...] Read more.
The paper presents the response of two geodesic domes under seismic excitations. The structures subjected to seismic analysis were created by two different methods of subdividing spherical triangles (the original octahedron face), as proposed by Fuliński. These structures are characterised by the similar number of elements. The structures are made of steel, which is a material that undoubtedly gives lightness to structures and allows large spans. Designing steel domes is currently a challenge for constructors, as well as architects, who take into account their aesthetic considerations. The analysis was carried out using the finite element method of the numerical program. The two designed domes were analysed using four different seismic excitations. The analysis shows what influence particular earthquakes have on the geodesic dome structures by two different methods. The study analysed the maximum displacements, axial forces, velocities, and accelerations of the designed domes. In addition, the Time History method was used for the analysis, which enabled the analysis of the structure in the time domain. The study will be helpful in designing new structures in seismic areas and in assessing the strength of various geodesic dome structures under seismic excitation. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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16 pages, 7903 KiB  
Article
Interlaboratory Comparative Tests in Ready-Mixed Concrete Quality Assessment
by Izabela Skrzypczak, Agnieszka Leśniak, Piotr Ochab, Monika Górka, Wanda Kokoszka and Anna Sikora
Materials 2021, 14(13), 3475; https://doi.org/10.3390/ma14133475 - 22 Jun 2021
Cited by 10 | Viewed by 1991
Abstract
Proper quality assessment of ready-mixed concrete, which is currently the principal material for construction, land engineering and architecture, has an impact on the optimisation and verification of correct functioning of individual stages of the production process. According to the European Standard EN 206 [...] Read more.
Proper quality assessment of ready-mixed concrete, which is currently the principal material for construction, land engineering and architecture, has an impact on the optimisation and verification of correct functioning of individual stages of the production process. According to the European Standard EN 206 “Concrete–Specification, performance, production and conformity”, obligatory conformity control of concrete is carried out by the producer during its production. In order to verify the quality of concrete, investors generally commission independent laboratory units to perform quality assessment of both concrete mix and hardened concrete, which guarantees a high quality of construction works. One of the essential tools for ensuring the quality of test results is the participation of laboratories in the so-called proficiency testing (PT) or inter-laboratory comparisons (ILC). Participation in PT/ILC programmes is, on the one hand, a tool for demonstrating the laboratory’s performance, on the other hand an aid for maintaining the quality of available concrete tests and validating test methods. Positive evaluation is a confirmation of the laboratory’s capability for performing the tests. The paper presents the results of laboratory proficiency tests carried out by means of inter-laboratory comparisons, as shown in the example of quality assessment of ready-mixed concrete for nine participating laboratories. The tests were performed for concrete of the following parameters: strength class C30/37, consistency S3, frost resistance degree F150, and water resistance degree W8. This involved determining consistencies, air content and density of the concrete mix, and compressive strength of hardened concrete. For the evaluation of laboratory performance results, z-score, ζ-score and En-score were applied. The innovation of the proposed study lies in employing both classical and iterative robust statistical methods. In comparison with classical statistical methods, robust methods ensure a smaller impact of outliers and other anomalies on the measurement results. Following the analyses, clear differences were found between the types of detected discrepancy of test results, which occurred due to the nature of individual parameters. For two laboratories, two scores revealed unsatisfactory results for concrete mix consistency. The main reasons can be pouring into the cone-shaped form a concrete mixture that is too dry, or incorrect use of a measuring tool also creating a possibility that the obtained value can be wrongly recorded. Other possible reasons are discussed in the paper. Participation in inter-laboratory comparison programmes is undoubtedly a way to verify and raise the quality of tests performed for concrete mix and hardened concrete, whereas individual analysis of the results allows the laboratory quality system to be improved. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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30 pages, 8031 KiB  
Article
Use of the AE Effect to Determine the Stresses State in AAC Masonry Walls under Compression
by Radosław Jasiński, Krzysztof Stebel and Paweł Kielan
Materials 2021, 14(13), 3459; https://doi.org/10.3390/ma14133459 - 22 Jun 2021
Cited by 8 | Viewed by 1530
Abstract
Safety and reliability of constructions operated are predicted using the known mechanical properties of materials and geometry of cross-sections, and also the known internal forces. The extensometry technique (electro-resistant tensometers, wire gauges, sensor systems) is a common method applied under laboratory conditions to [...] Read more.
Safety and reliability of constructions operated are predicted using the known mechanical properties of materials and geometry of cross-sections, and also the known internal forces. The extensometry technique (electro-resistant tensometers, wire gauges, sensor systems) is a common method applied under laboratory conditions to determine the deformation state of a material. The construction sector rarely uses ultrasonic extensometry with the acoustoelastic (AE) method which is based on the relation between the direction of ultrasonic waves and the direction of normal stresses. It is generally used to identify stress states of machine or vehicles parts, mainly made of steel, characterized by high homogeneity and a lack of inherent internal defects. The AE effect was detected in autoclaved aerated concrete (AAC), which is usually used in masonry units. The acoustoelastic effect was used in the tests described to identify the complex stress state in masonry walls (masonry units) made of AAC. At first, the relationships were determined for mean hydrostatic stresses P and mean compressive stresses σ3 with relation to velocities of the longitudinal ultrasonic wave cp. These stresses were used to determine stresses σ3. The discrete approach was used which consists in analyzing single masonry units. Changes in velocity of longitudinal waves were identified at a test stand to control the stress states of an element tested by the digital image correlation (DIC) technique. The analyses involved density and the impact of moisture content of AAC. Then, the method was verified on nine walls subjected to axial compression and the model was validated with the FEM micromodel. It was demonstrated that mean compressive stresses σ3 and hydrostatic stresses, which were determined for the masonry using the method considered, could be determined even up to ca. 75% of failure stresses at the acceptable error level of 15%. Stresses σ1 parallel to bed joints were calculated using the known mean hydrostatic stresses and mean compressive stresses σ3. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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14 pages, 5650 KiB  
Article
Effect of Confining Conditions on the Hydraulic Conductivity Behavior of Fiber-Reinforced Lime Blended Semiarid Soil
by Abdullah Ali Shaker, Mosleh Ali Al-Shamrani, Arif Ali Baig Moghal and Kopparthi Venkata Vydehi
Materials 2021, 14(11), 3120; https://doi.org/10.3390/ma14113120 - 06 Jun 2021
Cited by 13 | Viewed by 2863
Abstract
The hydraulic properties of expansive soils are affected due to the formation of visible cracks in the dry state. Chemical stabilization coupled with fiber reinforcement is often considered an effective strategy to improve the geotechnical performance of such soils. In this study, hydraulic [...] Read more.
The hydraulic properties of expansive soils are affected due to the formation of visible cracks in the dry state. Chemical stabilization coupled with fiber reinforcement is often considered an effective strategy to improve the geotechnical performance of such soils. In this study, hydraulic conductivity tests have been conducted on expansive clay using two different types of fibers (fiber cast (FC) and fiber mesh (FM)) exhibiting different surface morphological properties. The fiber parameters include their dosage (added at 0.2% to 0.6% by dry weight of soil) and length (6 and 12 mm). Commercially available lime is added to ensure proper bonding between clay particles and fiber materials, and its dosage was fixed at 6% (by dry weight of the soil). Saturated hydraulic conductivity tests were conducted relying on a flexible wall permeameter on lime-treated fiber-blended soil specimens cured for 7 and 28 days. The confining pressures were varied from 50 to 400 kPa, and the saturated hydraulic conductivity values (ksat) were determined. For FC fibers, an increase in fiber dosage caused ksat values to increase by 9.5% and 94.3% for the 6 and 12 mm lengths, respectively, at all confining pressures and curing periods. For FM fibers, ksat values for samples mixed with 6 mm fiber increased by 12 and 99.2% for 6 and 12 mm lengths, respectively for all confining pressures at the end of the 28-day curing period. The results obtained from a flexible wall permeameter (FWP) were compared with those of a rigid wall permeameter (RWP) available in the literature, and the fundamental mechanism responsible for such variations is explained. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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16 pages, 8058 KiB  
Article
On Characteristics of Ferritic Steel Determined during the Uniaxial Tensile Test
by Ihor Dzioba, Sebastian Lipiec, Robert Pala and Piotr Furmanczyk
Materials 2021, 14(11), 3117; https://doi.org/10.3390/ma14113117 - 06 Jun 2021
Cited by 13 | Viewed by 2305
Abstract
Tensile uniaxial test is typically used to determine the strength and plasticity of a material. Nominal (engineering) stress-strain relationship is suitable for determining properties when elastic strain dominates (e.g., yield strength, Young’s modulus). For loading conditions where plastic deformation is significant (in front [...] Read more.
Tensile uniaxial test is typically used to determine the strength and plasticity of a material. Nominal (engineering) stress-strain relationship is suitable for determining properties when elastic strain dominates (e.g., yield strength, Young’s modulus). For loading conditions where plastic deformation is significant (in front of a crack tip or in a neck), the use of true stress and strain values and the relationship between them are required. Under these conditions, the dependence between the true values of stresses and strains should be treated as a characteristic—a constitutive relationship of the material. This article presents several methodologies to develop a constitutive relationship for S355 steel from tensile test data. The constitutive relationship developed was incorporated into a finite element analysis of the tension test and verified with the measured tensile test data. The method of the constitutive relationship defining takes into account the impact of high plastic strain, the triaxiality stress factor, Lode coefficient, and material weakness due to the formation of microvoids, which leads to obtained correctly results by FEM (finite elements method) calculation. The different variants of constitutive relationships were applied to the FEM loading simulation of the three-point bending SENB (single edge notched bend) specimen to evaluate their applicability to the calculation of mechanical fields in the presence of a crack. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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16 pages, 8395 KiB  
Article
Non-Destructive Diagnostics of Concrete Beams Strengthened with Steel Plates Using Modal Analysis and Wavelet Transform
by Magdalena Knak, Erwin Wojtczak and Magdalena Rucka
Materials 2021, 14(11), 3014; https://doi.org/10.3390/ma14113014 - 02 Jun 2021
Cited by 10 | Viewed by 2191
Abstract
Externally bonded reinforcements are commonly and widely used in civil engineering objects made of concrete to increase the structure load capacity or to minimize the negative effects of long-term operation and possible defects. The quality of adhesive bonding between a strengthened structure and [...] Read more.
Externally bonded reinforcements are commonly and widely used in civil engineering objects made of concrete to increase the structure load capacity or to minimize the negative effects of long-term operation and possible defects. The quality of adhesive bonding between a strengthened structure and steel or composite elements is essential for effective reinforcement; therefore, there is a need for non-destructive diagnostics of adhesive joints. The aim of this paper is the detection of debonding defects in adhesive joints between concrete beams and steel plates using the modal analysis approach. The inspection was based on modal shapes and their further processing with the use of continuous wavelet transform (CWT) for precise debonding localization and imaging. The influence of the number of wavelet vanishing moments and the mode shape interpolation on damage imaging maps was studied. The results showed that the integrated modal analysis and wavelet transform could be successfully applied to determine the exact shape and position of the debonding in the adhesive joints of composite beams. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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27 pages, 13571 KiB  
Article
Shear Capacity and Behaviour of Bending Reinforced Concrete Beams Made of Steel Fibre-Reinforced Waste Sand Concrete
by Marek Lehmann and Wiesława Głodkowska
Materials 2021, 14(11), 2996; https://doi.org/10.3390/ma14112996 - 01 Jun 2021
Cited by 10 | Viewed by 2343
Abstract
Inthis paper, we report the results of our research on reinforced concrete beams made of fine aggregate fibre composite, with the addition of steel fibres at 1.2% of the composite volume. The fine aggregate fibre composite is a novel construction material, in which [...] Read more.
Inthis paper, we report the results of our research on reinforced concrete beams made of fine aggregate fibre composite, with the addition of steel fibres at 1.2% of the composite volume. The fine aggregate fibre composite is a novel construction material, in which the aggregate used is a post-production waste. Twenty reinforced concrete beams with varying degree of shear reinforcement, in the form of stirrups with and without the addition of steel fibres, tested under loading. The shear capacity results of reinforced concrete beams made of the fine aggregate fibre composite being bent by a transversal force, as well as the cracking forces causing the appearance of the first diagonal crack, are discussed. The stages of functioning of such elements are described. Furthermore, the effect of the steel fibres on the reduction of diagonal cracking is analysed. Computation of the shear capacity of the tested elements is performed, based on the Model Code 2010 and RILEM TC-162 TDF standards, for two variants of the compression strut inclination angle θ that measured during testing, and the minimum(in accordance with the Model Code 2010 standard). We found that the SMCFT method part of Model Code 2010 showed the best compatibility with the experimental results. The tests and analyses performed demonstrate that the developed novel fibrecomposite—the properties of which are close to, or better than, those of the ordinary concrete—can be used successfully for the manufacturing of construction elements in the shear capacity aspect. The developed fine aggregate fibrecomposite could serve, in some applications, as an alternative to ordinary concrete. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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17 pages, 14149 KiB  
Article
Analysis of the Possibility of Plastic Deformation Characterisation in X2CrNi18-9 Steel Using Measurements of Electromagnetic Parameters
by Maciej Roskosz, Krzysztof Fryczowski, Lechosław Tuz, Jianbo Wu, Krzysztof Schabowicz and Dominik Logoń
Materials 2021, 14(11), 2904; https://doi.org/10.3390/ma14112904 - 28 May 2021
Cited by 5 | Viewed by 2128
Abstract
An analysis was conducted on the possibility of making an assessment of the degree of plastic deformation ε in X2CrNi18-9 steel by measuring three electromagnetic diagnostic signals: the Barkhausen noise features, the impedance components in in-series LCR circuits, and the residual magnetic field [...] Read more.
An analysis was conducted on the possibility of making an assessment of the degree of plastic deformation ε in X2CrNi18-9 steel by measuring three electromagnetic diagnostic signals: the Barkhausen noise features, the impedance components in in-series LCR circuits, and the residual magnetic field components. The impact of ε on a series of different extracted features of diagnostic signals was investigated. The occurrence of two regions of sensitivity was found for all the features of the analysed signals. The two regions were separated by the following critical deformation value: ε ~ 10% for the components of the residual magnetic field and ε ~ 15% for the normalised components of impedance. As for the Barkhausen noise signal, the values were as follows: ε ~ 20% for the mean value, ε ~ 20% for the peak value of the signal envelope, and ε ~ 5% for the total number of the signal events. Metallographic tests were performed, which revealed essential changes in the microstructure of the tested material for the established critical values. The martensite transformation occurring during the plastic deformation process of X2CrNi18-9 austenitic steel process generated a magnetic phase. This magnetic phase was strong enough to relate the strain state to the values of diagnostic signals. The changes in the material electromagnetic properties due to martensitic transformation (γ → α’) began much earlier than indicated by the metallographic testing results. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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19 pages, 8644 KiB  
Article
Mechanical Properties of Polyurethane Adhesive Bonds in a Mineral Wool-Based External Thermal Insulation Composite System for Timber Frame Buildings
by Ewa Sudoł and Ewelina Kozikowska
Materials 2021, 14(10), 2527; https://doi.org/10.3390/ma14102527 - 13 May 2021
Cited by 11 | Viewed by 2957
Abstract
This paper aims to provide a preliminary assessment of polyurethane adhesive applicability as an alternative to conventional cement-based adhesives used to fix thermal insulation materials to substrates concerning mineral wool-based external thermal insulation composite systems. Currently, polyurethane adhesives are only used in expanded [...] Read more.
This paper aims to provide a preliminary assessment of polyurethane adhesive applicability as an alternative to conventional cement-based adhesives used to fix thermal insulation materials to substrates concerning mineral wool-based external thermal insulation composite systems. Currently, polyurethane adhesives are only used in expanded polystyrene-based ETICS. This study discusses the suitability of polyurethane adhesive for ETICS with lamella mineral-wool for timber frame buildings. Bond strength, shear strength and shear modulus tests were conducted. In addition, microstructure and apparent density were analysed. Mechanical properties were analysed in terms of the influence of substrate type and thermal and moisture conditions, taking into account solutions typical for sheathing on timber frame (oriented strand boards (OSB), fibre-reinforced gypsum boards (FGB) and cement-bonded particleboards (CPB)), as well as limit conditions for adhesive application. It was found that PU adhesive can achieve adhesion, both to MW and OSB, and FGB and CPB at ≥80 kPa, which is considered satisfactory for PU adhesives for EPS-based ETICS. Favourable shear properties were also obtained. There was no significant effect of sheathing type on the properties considered, but the influence of temperature and relative humidity, in which the bonds were made, was spotted. The results obtained can be considered promising in further assessing the usefulness of PU adhesives for MW-based ETICS. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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19 pages, 7733 KiB  
Article
Mechanical Properties and Damage Evolution of Concrete Materials Considering Sulfate Attack
by Qianyun Wu, Qinyong Ma and Xianwen Huang
Materials 2021, 14(9), 2343; https://doi.org/10.3390/ma14092343 - 30 Apr 2021
Cited by 17 | Viewed by 2048
Abstract
In order to study the durability of concrete materials subjected to sulfate attack, in a sulfate attack environment, a series of concrete tests considering different fly ash contents and erosion times were conducted. The mechanical properties and the micro-structure of concrete under sulfate [...] Read more.
In order to study the durability of concrete materials subjected to sulfate attack, in a sulfate attack environment, a series of concrete tests considering different fly ash contents and erosion times were conducted. The mechanical properties and the micro-structure of concrete under sulfate attack were studied based on the following: uniaxial compressive strength test, split tensile test, ultrasonic impulse method, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The mechanical properties were compressive strength, splitting tensile strength, and relative dynamic elastic modulus, respectively. Additionally, according to the damage mechanical theory, experimental results and micro-structure analysis, the damage evolution process of concrete under a sulfate attack environment were studied in detail. Finally, according to the sulfate attack time and fly ash content, a damage model of the sulfate attack of the binary surface was established. The specific results are as follows: under the action of sulfate attack, the change law of the rate of mass change, relative dynamic modulus of elasticity, corrosion resistance coefficient of compressive strength, and the corrosion resistance coefficient of the splitting tensile strength of concrete all increase first and then decrease. Under the same erosion time, concrete mixed with 10% fly ash content has the best sulfate resistance. Through data regression, the damage evolution equation of the sulfate attack was developed and there is an exponential function relationship among the different damage variables. The binary curved surface regression effect of the concrete damage and the erosion time and the amount of fly ash is significant, which can predict deterioration of concrete damage under sulfate attack. During the erosion time, the combined expansion of ettringite and gypsum caused micro cracks. With an increase of corrosion time, micro cracks developed and their numbers increased. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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18 pages, 3912 KiB  
Article
Development of Impact-Echo Multitransducer Device for Automated Concrete Homogeneity Assessment
by Bartłomiej Sawicki, Tomasz Piotrowski and Andrzej Garbacz
Materials 2021, 14(9), 2144; https://doi.org/10.3390/ma14092144 - 23 Apr 2021
Cited by 3 | Viewed by 2180
Abstract
A combination of multiple nondestructive testing (NDT) methods speeds up the assessment of concrete and increases the precision. This is why the UIR-Scanner was developed at Warsaw University of Technology. The scanner uses an Impact-Echo (IE) method with a unique arrangement of multiple [...] Read more.
A combination of multiple nondestructive testing (NDT) methods speeds up the assessment of concrete and increases the precision. This is why the UIR-Scanner was developed at Warsaw University of Technology. The scanner uses an Impact-Echo (IE) method with a unique arrangement of multiple transducers. This paper presents the development of the IE module using numerical models validated with experimental testing. It was found that rectangular arrangement of four transducers with the impactor in the middle is optimal for quick scanning of area for faults and discontinuities, changing the method from punctual to volumetric. A numerical study of void detectability depending on its position with respect to the IE module is discussed as well. After confirmation of the findings of models using experimental tests, the module was implemented into the scanner. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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26 pages, 6519 KiB  
Article
Estimating Mechanical Properties of Wood in Existing Structures—Selected Aspects
by Tomasz Nowak, Filip Patalas and Anna Karolak
Materials 2021, 14(8), 1941; https://doi.org/10.3390/ma14081941 - 13 Apr 2021
Cited by 23 | Viewed by 2851
Abstract
The paper presents and discusses selected methods of wood classification and the evaluation of its mechanical properties. Attention was mainly paid to methods that may be particularly useful for examining existing elements and structures. The possibility of estimating the modulus of rupture—MOR and [...] Read more.
The paper presents and discusses selected methods of wood classification and the evaluation of its mechanical properties. Attention was mainly paid to methods that may be particularly useful for examining existing elements and structures. The possibility of estimating the modulus of rupture—MOR and modulus of elasticity—MOE based on the non- destructive (NDT), semi-destructive (SDT), and destructive tests (DT) were considered. Known international, European, and American standards and research approaches were indicated. The selected testing methods and their interpretation were presented. These were, among others, the method of visual assessment, the resistance drilling method, methods of determining the dynamic modulus of elasticity, and procedures for testing small clear specimens. Moreover, some of our own research results from the conducted experimental tests were presented and discussed. In the destructive tests, both large elements and small clear specimens were examined. The results obtained from individual methods were compared and some conclusions were presented. The summary discusses the fundamental difficulties and limitations in applying the presented procedures and interpretations. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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Review

Jump to: Research

16 pages, 826 KiB  
Review
Concrete Containing Waste Glass as an Environmentally Friendly Aggregate: A Review on Fresh and Mechanical Characteristics
by Shaker Qaidi, Hadee Mohammed Najm, Suhad M. Abed, Yasin Onuralp Özkılıç, Husam Al Dughaishi, Moad Alosta, Mohanad Muayad Sabri Sabri, Fadi Alkhatib and Abdalrhman Milad
Materials 2022, 15(18), 6222; https://doi.org/10.3390/ma15186222 - 07 Sep 2022
Cited by 127 | Viewed by 5788
Abstract
The safe disposal of an enormous amount of waste glass (WG) in several countries has become a severe environmental issue. In contrast, concrete production consumes a large amount of natural resources and contributes to environmental greenhouse gas emissions. It is widely known that [...] Read more.
The safe disposal of an enormous amount of waste glass (WG) in several countries has become a severe environmental issue. In contrast, concrete production consumes a large amount of natural resources and contributes to environmental greenhouse gas emissions. It is widely known that many kinds of waste may be utilized rather than raw materials in the field of construction materials. However, for the wide use of waste in building construction, it is necessary to ensure that the characteristics of the resulting building materials are appropriate. Recycled glass waste is one of the most attractive waste materials that can be used to create sustainable concrete compounds. Therefore, researchers focus on the production of concrete and cement mortar by utilizing waste glass as an aggregate or as a pozzolanic material. In this article, the literature discussing the use of recycled glass waste in concrete as a partial or complete replacement for aggregates has been reviewed by focusing on the effect of recycled glass waste on the fresh and mechanical properties of concrete. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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36 pages, 12295 KiB  
Review
A Literature Review of Concrete Ability to Sustain Strength after Fire Exposure Based on the Heat Accumulation Factor
by Michał Pasztetnik and Roman Wróblewski
Materials 2021, 14(16), 4719; https://doi.org/10.3390/ma14164719 - 21 Aug 2021
Cited by 5 | Viewed by 3055
Abstract
Concrete is susceptible to damage during and after high-temperature exposure (most frequently in fire). The concrete partial strength re-gain after a high-temperature exposure obtained by the rehydration process is undoubtedly an advantage of this construction material. However, to use fire-damaged concrete, one has [...] Read more.
Concrete is susceptible to damage during and after high-temperature exposure (most frequently in fire). The concrete partial strength re-gain after a high-temperature exposure obtained by the rehydration process is undoubtedly an advantage of this construction material. However, to use fire-damaged concrete, one has to know why the strength deteriorates and what makes the partial re-gain. Within this framework, the paper aims to find what factors influence the strength re-gain. Moreover, an attempt is made to introduce a measure collecting various influences such as the modified heat accumulation factor—accounting only for that which is important for the process, the temperature decomposing cement paste (i.e., above 400 °C). Several factors, i.e., peak temperature, heating time and rate, cooling regime, post-fire re-curing, concrete composition, age of concrete at exposure, porosity, load level at exposure, and heat accumulation are presented by their influence on the relative residual compressive strength, i.e., a portion of initial strength that is obtained after temperature exposure and strength re-gain. Since the relative strength unifies various concretes, a more general assessment and discussion are presented based on the experimental results and correlation factors. As fundamental influences determining the residual strength, the heating time, peak temperature, cooling, or post-heating re-curing regimes are found with the load level at exposure being inadequately examined. This paper also shows the superiority of the modified heat accumulation factor, but the results obtained are not satisfactory, and additional experimental data are necessary to develop a theoretical model of the residual strength. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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28 pages, 3267 KiB  
Review
Some Microstructural Aspects of Ductile Fracture of Metals
by Wiktor Wciślik and Robert Pała
Materials 2021, 14(15), 4321; https://doi.org/10.3390/ma14154321 - 02 Aug 2021
Cited by 15 | Viewed by 3073
Abstract
The paper discusses the basic issues of the local approach to ductile fracture of structural metals, with particular emphasis on the failure due to microvoid development. The mechanisms of nucleation of voids around inclusions and precipitates are characterized. The criteria for the nucleation [...] Read more.
The paper discusses the basic issues of the local approach to ductile fracture of structural metals, with particular emphasis on the failure due to microvoid development. The mechanisms of nucleation of voids around inclusions and precipitates are characterized. The criteria for the nucleation of voids resulting from cracking of the existing particles or their separation from the material matrix are presented. Selected results of experimental studies and Finite Element Method (FEM) simulations on nucleation of voids are discussed. The analytical and numerical models of growth and coalescence of voids are described, indicating the effect of the stress state components on the morphology of voids and the course of the cracking on a microscopic scale. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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21 pages, 2223 KiB  
Review
Deterioration and Protection of Concrete Elements Embedded in Contaminated Soil: A Review
by Ginneth Patricia Millán Ramírez, Hubert Byliński and Maciej Niedostatkiewicz
Materials 2021, 14(12), 3253; https://doi.org/10.3390/ma14123253 - 12 Jun 2021
Cited by 9 | Viewed by 2211
Abstract
Coating materials are considered one of the most antique materials of human civilization; they have been used for decoration and the protection of surfaces for millennia. Concrete structures—due to their permanent exposure to different types of environments and contaminants—require the use of coatings [...] Read more.
Coating materials are considered one of the most antique materials of human civilization; they have been used for decoration and the protection of surfaces for millennia. Concrete structures—due to their permanent exposure to different types of environments and contaminants—require the use of coatings that contribute to its preservation by reducing the corrosion of its components (steel and aggregates). This article intends to introduce the principal causes of concrete deterioration and the coating materials used to protect concrete structures, including a summary of the coating types, their advantages and disadvantages, and the latest developments and applications. Furthermore, this paper also assesses brief information about the potential challenges in the production of eco-friendly coating materials. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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