Research

17 pages, 5769 KiB

Open AccessArticle

The Effect of Specimen Size on Acoustic Emission Parameters and Approximate Position of Defects Obtained during Destructive Testing of Cementitious and Alkali-Activated Degraded Fine-Grained Materials

by Libor Topolář, Dalibor Kocáb, Petr Hrubý, Luboš Jakubka, Michaela Hoduláková and Romana Halamová

Materials 2023, 16(9), 3527; https://doi.org/10.3390/ma16093527 - 04 May 2023

Viewed by 987

Abstract

Two sizes of test samples were selected to investigate the effect of size on the level of degradation. The smaller test specimens had dimensions of 40 × 40 × 160 mm, and the larger ones had dimensions of 100 × 100 × 400 [...] Read more.

Two sizes of test samples were selected to investigate the effect of size on the level of degradation. The smaller test specimens had dimensions of 40 × 40 × 160 mm, and the larger ones had dimensions of 100 × 100 × 400 mm. Both sizes of test specimens were always made of the same mortar. In one case, Blast Furnace Cement was chosen as the binder. In the other case, it was an alkali-activated material as a possibly more environmentally economical substitute. Both types of material were deposited in three degrading solutions: magnesium sulphate, ammonium nitrate and acetic acid. The reference set was stored in a water bath. After six months in the degradation solutions, a static elastic modulus was determined for the specimens during this test, and the acoustic emission was measured. Acoustic emission parameters were evaluated: the number of hits, the amplitude magnitude and a slope from the amplitude magnitude versus time (this slope should correspond to the Kaiser effect). For most of the parameters studied, the size effect was more evident for the more degraded specimens, i.e., those placed in aggressive solutions. The approximate location of emerging defects was also determined using linear localisation for smaller specimens where the degradation effect was more significant. In more aggressive environments (acetic acid, ammonium nitrate), the higher resistance of materials based on alkaline-activated slag was more evident, even in the case of larger test bodies. The experiments show that the acoustic emission results agree with the results of the static modulus of elasticity. Full article

(This article belongs to the Special Issue Research on Non-destructive Testing in Civil Engineering Materials)

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14 pages, 2791 KiB

Open AccessArticle

Optimal Design of Bubble Deck Concrete Slabs: Sensitivity Analysis and Numerical Homogenization

by Natalia Staszak, Tomasz Garbowski and Barbara Ksit

Materials 2023, 16(6), 2320; https://doi.org/10.3390/ma16062320 - 14 Mar 2023

Cited by 2 | Viewed by 1425

Abstract

The use of layered or hollow floors in the construction of buildings obviously reduces the self-weight of the slab, and their design requires some expertise. In the present work, a sensitivity analysis and numerical homogenization were used to select the most important characteristics [...] Read more.

The use of layered or hollow floors in the construction of buildings obviously reduces the self-weight of the slab, and their design requires some expertise. In the present work, a sensitivity analysis and numerical homogenization were used to select the most important characteristics of bubble deck floors that have a direct or indirect impact on their load capacity. From the extensive case study, conclusions were drawn regarding the optimal selection of geometry, materials, and the arrangement and size of air voids in such a way as to ensure high stiffness of the cross-section and at the same time maximally reduce the self-weight of the slabs. The conducted analyses showed that the height of the slab and the geometry of the voids had the greatest impact on the load-bearing capacity. The concrete class and reinforcement used are of secondary importance in the context of changes in load-bearing capacity. Both the type of steel and the amount of reinforcement has a rather small or negligible influence on the bubble deck stab stiffness. Of course, the geometry of the voids and their arrangement and shape have the greatest influence on the drop in the self-weight of the floor slabs. Based on the presented results of the sensitivity analysis combined with numerical homogenization, a set of the most important design parameters was ordered and selected for use in the optimization procedure. Full article

(This article belongs to the Special Issue Research on Non-destructive Testing in Civil Engineering Materials)

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16 pages, 6997 KiB

Open AccessArticle

Influence of Actual Curing Conditions on Mechanical Properties of Concrete in Bridge Superstructures

by Jakub Krząkała, Piotr Łaziński, Michael Gerges, Łukasz Pyrzowski and Grzegorz Grządziela

Materials 2023, 16(1), 54; https://doi.org/10.3390/ma16010054 - 21 Dec 2022

Cited by 3 | Viewed by 978

Abstract

This article presents the research on the mechanical characteristics of concrete in the construction of three concrete bridges. A system of recording the internal temperature of concrete and automatic control of laboratory ovens was used for specimen curing. This allowed the specimens to [...] Read more.

This article presents the research on the mechanical characteristics of concrete in the construction of three concrete bridges. A system of recording the internal temperature of concrete and automatic control of laboratory ovens was used for specimen curing. This allowed the specimens to be cured under conditions similar to those occurring in the structure. Before the construction, reference blocks were used to define similar curing conditions. Maximum setting temperatures ranged from 47.6 °C to 62.0 °C and had a favorable effect on the properties of the concrete at an early age. For concretes with the use of CEM I cement, after 3 days of curing, the strength obtained was up to 8.2 MPa (23%) higher than that for specimens cured under standard conditions. The modulus of elasticity was higher up to 4.9 GPa (21%). For concrete with the use of CEM III cement, these differences were 26.9 MPa (174%) and 10.3 GPa (64%), respectively. After 7 days of curing, the results were close to each other and after 14, 28, and 56 days, higher values were obtained for specimens cured under standard conditions. The value of the modulus of elasticity of concrete was determined using the direct method according to Eurocode and the standard A method. A test load of the bridge was carried out to verify the modulus values obtained from laboratory tests. The highest consistency (99%) between the theoretical deflections and those measured in the test load was achieved when using the stabilized modulus values obtained on specimens cured under structure conditions in the FEM model. The research confirms the necessity of determining the mechanical characteristics of concrete with taking into account the curing conditions of concrete in the structure. A procedure for determining the mechanical properties of concrete for the correct construction of a bridge is proposed. These results can also be used in the development of a digital twin for bridge management. Full article

(This article belongs to the Special Issue Research on Non-destructive Testing in Civil Engineering Materials)

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21 pages, 6435 KiB

Open AccessArticle

Bridge Non-Destructive Measurements Using a Laser Scanning during Acceptance Testing: Case Study

by Pawel Tysiac, Mikolaj Miskiewicz and Dawid Bruski

Materials 2022, 15(23), 8533; https://doi.org/10.3390/ma15238533 - 30 Nov 2022

Cited by 3 | Viewed by 1580

Abstract

Owing to the recent proliferation of inventory works on roads and railways, bridge acceptance tests have increased exponentially. These tests’ results are often misinterpreted owing to the use of various measuring equipment types, rendering integrated interpretation problematic. It is also problematic that adjusting [...] Read more.

Owing to the recent proliferation of inventory works on roads and railways, bridge acceptance tests have increased exponentially. These tests’ results are often misinterpreted owing to the use of various measuring equipment types, rendering integrated interpretation problematic. It is also problematic that adjusting the measurement method is difficult when the structure’s response to load is uncertain. Therefore, it is important to observe the largest possible range of possible deformations. For this reason, the present study suggests a novel approach to bridge non-destructive measurements using a laser scanner during acceptance testing. The main advantage of our method is the ability it affords to observe all points of the structure during testing, an ability that is extremely important is the absence of unambiguous data regarding the bridge’s condition. To significantly increase the scanning accuracy (up to 0.5 mm), measurements from a limited number of linear sensors are used (whose accuracy is up to 0.1 mm). To achieve optimal accuracy, we performed the following steps: first, we adapted the precision requirements to the numerical project. For this purpose, we used potentiometric sensors to measure linear deformations. Next, we performed laser scanning measurements from two scan positions. Finally, we filtered the data for the selected cross-section and modelled the points into polynomial deflection. The performed tests confirmed that the structure’s response was as predicted by the FEM model, and the object was approved for use. Our future tests will be based on the selection of a structure with minimal measurement errors, and the results will be compared using a total station, ensuring the highest possible quality of service, which can be repeated in simple steps. As study objects, we presented two items: the first without proper calibration on a linear sensor and the second using linear sensors to present the highest possible accuracy of our experiment. Full article

(This article belongs to the Special Issue Research on Non-destructive Testing in Civil Engineering Materials)

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16 pages, 3316 KiB

Open AccessArticle

Non-Destructive Evaluation of Mortar with Ground Granulated Blast Furnace Slag Blended Cement Using Ultrasonic Pulse Velocity

by Chi Kang Loke, Barry Lehane, Farhad Aslani, Subhra Majhi and Abhijit Mukherjee

Materials 2022, 15(19), 6957; https://doi.org/10.3390/ma15196957 - 07 Oct 2022

Cited by 6 | Viewed by 1086

Abstract

Non-destructive evaluation using ultrasonic pulse velocity (V_p) testing has extensive applications in the concrete industry. With advances in construction technology, the use of ground granulated blast furnace slag (GGBFS) as a partial replacement to cement in a concrete mix is [...] Read more.

Non-destructive evaluation using ultrasonic pulse velocity (V_p) testing has extensive applications in the concrete industry. With advances in construction technology, the use of ground granulated blast furnace slag (GGBFS) as a partial replacement to cement in a concrete mix is growing in popularity primarily because it reduces the initial capital cost of raw materials and the associated energy costs. This paper investigates the effect of the water-to-cement (w_c) ratio and the cement content replaced by GGBFS on the development with time of the ultimate compressive strength (

f_{c}^{'}

) and the compression wave velocity (V_p) of mortar. The results showed that in the case of mortar with higher percentages of GGBFS replacement (where nucleation surfaces are more abundant), increasing w_c can increase

f_{c}^{'}

but cause a decrease in V_p. The posterior hydration process is highly dependent upon the water particles in the mixture after the first stage of hydration. After 7 days of curing, experimental results show that the

f_{c}^{'}

of slag blended cement mix design w_c ratio of 0.6 surpassed the

f_{c}^{'}

value of an Ordinary Portland cement. A regression model correlating the

f_{c}^{'}

and V_p of slag blended mortar is developed, which can be used to predict

f_{c}^{'}

at concrete ages ranging from 1 day to 28 days for mixes with GGBFS percentage replacement values ranging from 15% to 45%. Full article

(This article belongs to the Special Issue Research on Non-destructive Testing in Civil Engineering Materials)

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28 pages, 4490 KiB

Open AccessArticle

Method of Iterative Determination of the Polarized Area of Steel Reinforcement in Concrete Applied in the EIS Measurements

by Mariusz Jaśniok

Materials 2022, 15(9), 3274; https://doi.org/10.3390/ma15093274 - 03 May 2022

Cited by 1 | Viewed by 1360

Abstract

A new method is proposed for determining the test surface of steel rebar in concrete during polarization measurements of corrosion rate of reinforcement using the method of Electrochemical Impedance Spectroscopy. The methodology was based on the original 3D model of the steel-concrete system, [...] Read more.

A new method is proposed for determining the test surface of steel rebar in concrete during polarization measurements of corrosion rate of reinforcement using the method of Electrochemical Impedance Spectroscopy. The methodology was based on the original 3D model of the steel-concrete system, in which traditional equivalent electrical systems were coupled with factors that accounted for the complex geometry of the test reinforced concrete element. The developed method worked with a rectangular counter electrode without a guard ring assist, during an individual impedance measurement. The impact of the counter electrode size on the impedance spectra was verified in the first stage by tests conducted with ten types of counter electrodes. The obtained results in the form of empirical spectra were represented by theoretical spectra using the 3D model and the matching degrees were within a range of 0.96–1.73 at the expected level of 1.00. The obtained results in the form of spectra distribution were accurately represented by simulations with the 3D model. In the second stage, the iterative procedure for determining the polarization area of reinforcement in concrete was positively verified for additional test elements. Electrochemical parameters of the steel-concrete system were determined on the basis of the 3D model with a simultaneous adjustment of the polarization area on the rebar. In this case, the expected matching degree of 1.00 was obtained for each tested system after more than ten iterations starting from matching the model spectra to the empirical spectra at the level of 0.31–0.93. Full article

(This article belongs to the Special Issue Research on Non-destructive Testing in Civil Engineering Materials)

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12 pages, 3531 KiB

Open AccessArticle

Relationship of Different Properties from Non-Destructive Testing of Heavy Concrete from Magnetite and Serpentinite

by Petr Lehner and Jacek Gołaszewski

Materials 2021, 14(15), 4288; https://doi.org/10.3390/ma14154288 - 31 Jul 2021

Cited by 5 | Viewed by 1510

Abstract

Radiation-shielding concrete has been analyzed by several methods of destructive and non-destructive testing (NDT). Concretes made of crushed basalt, magnetite, serpentinite, and two different types of cement (Portland cement CEM I and slag cement CEM III/A) were studied. In this study, we analyzed [...] Read more.

Radiation-shielding concrete has been analyzed by several methods of destructive and non-destructive testing (NDT). Concretes made of crushed basalt, magnetite, serpentinite, and two different types of cement (Portland cement CEM I and slag cement CEM III/A) were studied. In this study, we analyzed concrete columns with a height of 1200 mm and a cross-section of 200 × 200 mm². The top and bottom of the column were analyzed using data from compressive strength, dynamic modulus of elasticity, water penetration, and diffusion coefficients derived from the electrical resistivity test. This article presents the properties of fresh concrete and concrete after two years of setting. It was determined how the different ratios of basalt, magnetite, and serpentinite affect the individual measured parameters. Furthermore, correlation relations between individual resulting values were analyzed. It was observed that compressive strength generally does not correlate with other results. The diffusion coefficient correlated well with density and water penetration. Little or no correlation was observed in the diffusion coefficient with compressive strength and modulus of elasticity. The results of the study make it possible to refine the testing of heavy concretes in terms of electrical resistivity, and point to the possible use of NDT methods. The results also show which composition of heavy concrete is better in terms of effective diffusivity. Full article

(This article belongs to the Special Issue Research on Non-destructive Testing in Civil Engineering Materials)

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15 pages, 4504 KiB

Open AccessEditor’s ChoiceArticle

Moisture Distribution during Water Absorption of Ordinary Portland Cement Mortars Obtained with Low-Field Unilateral Magnetic Resonance

by Prisciliano Felipe de Jesús Cano-Barrita and Floriberto Díaz-Díaz

Materials 2021, 14(15), 4279; https://doi.org/10.3390/ma14154279 - 31 Jul 2021

Viewed by 1758

Abstract

Moisture distribution in cement-based materials is important from the durability point of view. In the present study, a portable three-magnet array with an elliptical surface radio frequency coil was used to undertake magnetic resonance measurements of moisture content in ordinary Portland cement mortar [...] Read more.

Moisture distribution in cement-based materials is important from the durability point of view. In the present study, a portable three-magnet array with an elliptical surface radio frequency coil was used to undertake magnetic resonance measurements of moisture content in ordinary Portland cement mortar and concrete samples. Measurements along the length of the samples during capillary water absorption produced moisture content profiles that were compared with reference profiles acquired using a magnetic resonance imaging instrument. Profiles obtained with the three-magnet array were similar in shape and in penetration depth to those acquired with magnetic resonance imaging. The correlation coefficient between the moisture content measured with both techniques was r² = 0.97. Similar values of saturated permeability of the mortars with identical w/c ratio were computed with the Hydrus 1D software based on the moisture content profiles. Additionally, inverse Laplace transformation of the signal decays provided the water-filled pore size distribution in saturated and unsaturated regions of the samples. The three-magnet array was successfully used to acquire nuclear magnetic resonance signal from a concrete sample, which was not possible with the magnetic resonance imaging instrument using the single-point imaging technique. Full article

(This article belongs to the Special Issue Research on Non-destructive Testing in Civil Engineering Materials)

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23 pages, 11014 KiB

Open AccessArticle

A Study on the Detection of Internal Defect Types for Duct Depth of Prestressed Concrete Structures Using Electromagnetic and Elastic Waves

by Young-Geun Yoon, Jae-Yun Lee, Hajin Choi and Tae-Keun Oh

Materials 2021, 14(14), 3931; https://doi.org/10.3390/ma14143931 - 14 Jul 2021

Cited by 6 | Viewed by 2025

Abstract

Prestressed concrete (PSC) is widely used for the construction of bridges. The collapse of several bridges with PSC has been reported, and insufficient grout and tendon corrosion were found inside the ducts of these bridges. Therefore, non-destructive testing (NDT) technology is important for [...] Read more.

Prestressed concrete (PSC) is widely used for the construction of bridges. The collapse of several bridges with PSC has been reported, and insufficient grout and tendon corrosion were found inside the ducts of these bridges. Therefore, non-destructive testing (NDT) technology is important for identifying defects inside ducts in PSC structures. Electromagnetic (EM) waves have limited detection of internal defects in ducts due to strong reflections from the surface of the steel ducts. Spectral analysis of the existing impact echo (IE) method is limited to specific conditions. Moreover, the flexural mode in upper defects of ducts located at a shallow depth and delamination defects inside ducts are not considered. In this study, the applicability of the elastic wave of IE was analyzed, and multichannel analysis of surface, EM, and shear waves was employed to evaluate six types of PSC structures. A procedure using EM waves, IE, and principal component analysis (PCA) was proposed for a more accurate classification of defect types inside ducts. The proposed procedure was effective in classifying upper, internal, and delamination defects of ducts under 100 mm in thickness, and it could be utilized up to 200 mm in the case of duct defect limitations. Full article

(This article belongs to the Special Issue Research on Non-destructive Testing in Civil Engineering Materials)

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18 pages, 7781 KiB

Open AccessArticle

Quantifying the Comprehensive Characteristics of Inclusion-Induced Defects Using an Integrated Destructive and Non-Destructive Method

by Rongfei Juan, Min Wang, Junhe Lian, Chao Gu, Lanxin Li and Yanping Bao

Materials 2021, 14(6), 1475; https://doi.org/10.3390/ma14061475 - 17 Mar 2021

Cited by 3 | Viewed by 1815

Abstract

Driven by the continuous improvement of the mechanical properties, especially the fatigue property of the high-strength steels, it is particularly important to characterize the type, size, and distribution of inclusions and the critical inclusions in the steel matrix, as they are decisive for [...] Read more.

Driven by the continuous improvement of the mechanical properties, especially the fatigue property of the high-strength steels, it is particularly important to characterize the type, size, and distribution of inclusions and the critical inclusions in the steel matrix, as they are decisive for the fatigue life performance. This paper presents an integrated approach for the comprehensive characterization of the inclusions in metals by combining the advantages of destructive methods based on metallography and non-destructive testing methods using ultrasonic detection technology. The position and size of inclusions were obtained by scanning ultrasonic microscope, and the composition and micro-image of inclusions were further analyzed by scanning electron microscope. According to the results obtained by the proposed approach, the distribution laws of oxide inclusions and sulfide inclusions in the samples were statistically analyzed, and then the maximum distribution analysis method was used to predict the maximum inclusions. We compare the predicted size value with the value obtained by the characterization method to establish a certain corresponding relationship. The results show that large defects in metals can be accurately characterized by the proposed method, and the size of inclusions predicted by extreme value analysis is close to that of the scanning electron microscope. The integrated destructive and non-destructive method can reveal the in situ information of inclusions and give the possible relationship between inclusions and process and material properties. Full article

(This article belongs to the Special Issue Research on Non-destructive Testing in Civil Engineering Materials)

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17 pages, 11078 KiB

Open AccessArticle

Indirect Determination of Residual Prestressing Force in Post-Tensioned Concrete Beam

by Jakub Kraľovanec, Martin Moravčík, Petra Bujňáková and Jozef Jošt

Materials 2021, 14(6), 1338; https://doi.org/10.3390/ma14061338 - 10 Mar 2021

Cited by 21 | Viewed by 2688

Abstract

A diagnostic survey on the precast prestressed bridge Nižná confirmed significant deterioration due to environmental distress. Evidently, decisive failures of the structure have a similar character as in the previous precast prestressed bridge in Podbiel in the northern part of Slovakia. These failures [...] Read more.

A diagnostic survey on the precast prestressed bridge Nižná confirmed significant deterioration due to environmental distress. Evidently, decisive failures of the structure have a similar character as in the previous precast prestressed bridge in Podbiel in the northern part of Slovakia. These failures result from the unsuitable concept of the first generation of precast prestressed concrete beams, which was used in the former Czechoslovakia in the second half of the 20th century. Subsequently, experimental verification using the proof-load test was also executed. This bridge was built in 1956, so at the time of testing, it was 60 years old. The paper presents the indirect determination of prestressing level in one precast post-tensioned concrete beam using the saw-cut method. Experimental measurement was executed during the bridge demolition. Subsequently, a 2D numerical model in ATENA 2D Software, with the assumption of nonlinear material behavior for verification of experimental results, was performed. Finally, the residual prestressing force was evaluated and compared with the expected state of prestressing according to Eurocodes after 60 years of service. Full article

(This article belongs to the Special Issue Research on Non-destructive Testing in Civil Engineering Materials)

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14 pages, 4374 KiB

Open AccessEditor’s ChoiceArticle

Effect of Moisture Distribution on Velocity and Waveform of Ultrasonic-Wave Propagation in Mortar

by Shinichiro Okazaki, Hiroma Iwase, Hiroyuki Nakagawa, Hidenori Yoshida and Ryosuke Hinei

Materials 2021, 14(4), 790; https://doi.org/10.3390/ma14040790 - 07 Feb 2021

Cited by 4 | Viewed by 1872

Abstract

Considering that the ultrasonic method is applied for the quality evaluation of concrete, this study experimentally and numerically investigates the effect of inhomogeneity caused by changes in the moisture content of concrete on ultrasonic wave propagation. The experimental results demonstrate that the propagation [...] Read more.

Considering that the ultrasonic method is applied for the quality evaluation of concrete, this study experimentally and numerically investigates the effect of inhomogeneity caused by changes in the moisture content of concrete on ultrasonic wave propagation. The experimental results demonstrate that the propagation velocity and amplitude of the ultrasonic wave vary for different moisture content distributions in the specimens. In the analytical study, the characteristics obtained experimentally are reproduced by modeling a system in which the moisture content varies between the surface layer and interior of concrete. Full article

(This article belongs to the Special Issue Research on Non-destructive Testing in Civil Engineering Materials)

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