Research

21 pages, 5567 KiB

Open AccessArticle

Strength Reduction Due to Acid Attack in Cement Mortar Containing Waste Eggshell and Glass: A Machine Learning-Based Modeling Study

by Fei Zhu, Xiangping Wu, Yijun Lu and Jiandong Huang

Buildings 2024, 14(1), 225; https://doi.org/10.3390/buildings14010225 - 14 Jan 2024

Cited by 5 | Viewed by 1120

Abstract

The present study utilized machine learning (ML) techniques to investigate the effects of eggshell powder (ESP) and recycled glass powder (RGP) on cement composites subjected to an acidic setting. A dataset acquired from the published literature was employed to develop machine learning-based predictive [...] Read more.

The present study utilized machine learning (ML) techniques to investigate the effects of eggshell powder (ESP) and recycled glass powder (RGP) on cement composites subjected to an acidic setting. A dataset acquired from the published literature was employed to develop machine learning-based predictive models for the cement mortar’s compressive strength (CS) decrease. Artificial neural network (ANN), K-nearest neighbor (KNN), and linear regression (LR) were chosen for modeling. Also, RreliefF analysis was performed to study the relevance of variables. A total of 234 data points were utilized to train/test ML algorithms. Cement, sand, water, silica fume, superplasticizer, glass powder, eggshell powder, and 90 days of CS were considered as input variables. The outcomes of the research showed that the employed models could be applied to evaluate the reduction percentage of CS in cement composites, including ESP and RGP, after being exposed to acid. Based on the R² values (0.87 for the ANN, 0.81 for the KNN, and 0.78 for LR), as well as the assessment of variation between test values and anticipated outcomes and errors (1.32% for ANN, 1.57% for KNN, and 1.69% for LR), it was determined that the accuracy of the ANN model was superior to the KNN and LR. The sieve diagram exhibited a correlation amongst the model predicted and target results. The outcomes of the RreliefF analysis suggested that ESP and RGP significantly influenced the CS loss of samples with RreliefF scores of 0.26 and 0.21, respectively. Based on the outcomes of the research, the ANN approach was determined suitable for predicting the CS loss of mortar subjected to acidic environments, thereby eliminating lab testing trails. Full article

(This article belongs to the Special Issue Advances in Methods for Performance Characterization and Prediction of Reinforced Concrete)

► Show Figures

Figure 1

21 pages, 8481 KiB

Open AccessArticle

Strength Estimation and Feature Interaction of Carbon Nanotubes-Modified Concrete Using Artificial Intelligence-Based Boosting Ensembles

by Fei Zhu, Xiangping Wu, Yijun Lu and Jiandong Huang

Buildings 2024, 14(1), 134; https://doi.org/10.3390/buildings14010134 - 04 Jan 2024

Cited by 5 | Viewed by 751

Abstract

The standard approach for testing ordinary concrete compressive strength (CS) is to cast samples and test them after different curing times. However, testing adds cost and time to projects, and, therefore, construction sites experience delays. Because carbon nanotubes (CNTs) vary in length, composition, [...] Read more.

The standard approach for testing ordinary concrete compressive strength (CS) is to cast samples and test them after different curing times. However, testing adds cost and time to projects, and, therefore, construction sites experience delays. Because carbon nanotubes (CNTs) vary in length, composition, diameter, and dispersion, experiment and formula fitting alone cannot reliably predict the strength of CNTs-based composites. For empirical equations or traditional statistical approaches to properly forecast complex materials’ mechanical characteristics, various significant parameters, databases, and nonlinear relationships between variables must be considered. Machine learning (ML) tools are the most advanced for accurate predictions of material behaviour. This study employed gradient boosting, light gradient boosting machine, and extreme gradient boosting techniques to forecast the CS of CNTs-modified concrete. Also, in order to explore the influence and interaction of various features, an interaction analysis was conducted. In terms of R², gradient boosting, light gradient boosting machine, and extreme gradient boosting models proved their accuracy. Extreme gradient boosting had the highest R² of 0.97, followed by light gradient boosting machine and gradient boosting with scores of 0.94 and 0.93, respectively. This type of research may help both academics and industry forecast material properties and influential elements, thereby reducing lab test requirements. Full article

(This article belongs to the Special Issue Advances in Methods for Performance Characterization and Prediction of Reinforced Concrete)

► Show Figures

Figure 1

12 pages, 1801 KiB

Open AccessArticle

Experimental Study on the Bonding Performance between Fiber-Belt-Bar and Concrete

by Wenhu Gu, Jiarui Chen, Qirong Li, Rundong Ji and Jianzhong Ji

Buildings 2023, 13(6), 1547; https://doi.org/10.3390/buildings13061547 - 17 Jun 2023

Cited by 1 | Viewed by 769

Abstract

Fiber materials have advantages such as light weight and high strength, corrosion resistance, fatigue resistance, and easy processing and production, and they are widely applied in the repair and renovation of concrete structures. To promote the construction convenience of fiber materials, fiber raw [...] Read more.

Fiber materials have advantages such as light weight and high strength, corrosion resistance, fatigue resistance, and easy processing and production, and they are widely applied in the repair and renovation of concrete structures. To promote the construction convenience of fiber materials, fiber raw yarn is continuously braided to form fiber-belt-bars. Based on the existing research, the performance of bonding between fiber-belt-bars and a concrete interface was investigated, and pull-out tests were performed to systematically investigate the effects of the fiber-belt-bar cross-sectional size, anchorage length, concrete strength, and fiber type on the bonding performance. The experimental results show that the bond strength reduces with an increase in the anchorage length, increase in cross-sectional size, and decrease in concrete strength, and the effect of fiber type on the bond strength is not obvious. On this basis, a formula for calculating the average bond strength of fiber-belt-bars is proposed. Experiments and calculations determined that the average bond strength between fiber-belt-bar and concrete with a cross-sectional size of 12 mm × 3 mm is 10–30% higher than that with a cross-sectional size of 20 mm × 3 mm for the same anchorage length. Finally, the minimum anchorage length of the fiber-belt-bar is proposed to provide a valuable reference for the use of fiber-belt-bar in concrete projects. Full article

(This article belongs to the Special Issue Advances in Methods for Performance Characterization and Prediction of Reinforced Concrete)

► Show Figures

Figure 1

15 pages, 5864 KiB

Open AccessArticle

Investigation on Shrinkage Characteristics of Polyester-Fiber-Reinforced Cement-Stabilized Concrete Considering Fiber Length and Content

by Jian Wang, Min Li, Jingchun Chen, Zedong Zhao, Hongbo Zhao, Lin Zhang and Jiaolong Ren

Buildings 2023, 13(4), 1027; https://doi.org/10.3390/buildings13041027 - 13 Apr 2023

Cited by 1 | Viewed by 1194

Abstract

Polyester-fiber-reinforced cement-stabilized concrete is widely adopted to prevent the shrinkage cracking in pavement engineering. However, the effects of fiber length and content on the dry shrinkage and temperature shrinkage are not clear. The relationship between shrinkage resistance and strength is also discussed scantily. [...] Read more.

Polyester-fiber-reinforced cement-stabilized concrete is widely adopted to prevent the shrinkage cracking in pavement engineering. However, the effects of fiber length and content on the dry shrinkage and temperature shrinkage are not clear. The relationship between shrinkage resistance and strength is also discussed scantily. Hence, five types of polyester fiber length (1 cm, 3 cm, 5 cm, 7 cm, and 9 cm) and six types of polyester fiber content (0.1‰, 0.3‰, 0.5‰, 0.7‰, 0.9‰, and 1.1‰) were selected to prepare the fiber-reinforced cement-stabilized concrete. The dry shrinkage coefficients and temperature shrinkage coefficients were used to evaluate the shrinkage resistance. Moreover, the relationships among these shrinkage coefficients, compressive strength, and splitting strength at different curing ages were investigated to realize the prediction of shrinkage resistance of polyester-fiber-reinforced cement-stabilized concrete. This study aimed to seek the optimal fiber characteristics and conveniently evaluate the shrinkage resistance for the polyester-fiber-reinforced cement-stabilized concrete. Results show that: increasing the content of polyester fiber can significantly improve the shrinkage resistance of cement-stabilized concrete, especially for the temperature shrinkage. The fiber length should not be too long, especially for dry shrinkage. The optimum fiber content and fiber length is 0.7‰ and 5 cm for the dry shrinkage resistance and 0.7‰ and 9 cm for the temperature shrinkage resistance. There was higher correlation between compressive strengths and shrinkage coefficients, while the correlation between splitting strength and shrinkage coefficients was not obvious. Full article

(This article belongs to the Special Issue Advances in Methods for Performance Characterization and Prediction of Reinforced Concrete)

► Show Figures

Figure 1

20 pages, 14010 KiB

Open AccessArticle

Early Strength Evolution of Cement Grouts Adopted in Reinforced Concrete Subjected to Na₂SO₄ Corrosion

by Yinshan Xu, Jianqiang Zhou and Sujing Jin

Buildings 2023, 13(3), 579; https://doi.org/10.3390/buildings13030579 - 21 Feb 2023

Viewed by 983

Abstract

Due to the harsh application environment, sodium sulfate corrosion poses a considerable threat to the performance of reinforced concrete. Considering high fluidization and early strength cement grouts (HECG) are widely adopted in the repair engineering of reinforced concrete, HECG are also subjected to [...] Read more.

Due to the harsh application environment, sodium sulfate corrosion poses a considerable threat to the performance of reinforced concrete. Considering high fluidization and early strength cement grouts (HECG) are widely adopted in the repair engineering of reinforced concrete, HECG are also subjected to the action of corrosive substances. Even though numerous research results disclosed the effect of sodium sulfate corrosion on the performance and the degradation mechanisms of conventional cement grouts, the degradation mechanisms of HECG under sodium sulfate corrosion are still to be studied because HECG have the exceptional characteristics of high fluidization and early strength that conventional cement grouts do not have. Hence, the compressive and flexural strengths of HECG after corrosion with different sodium sulfate solution concentrations and corrosion times were tested in this study. Moreover, the evolution of the microstructure of HECG in the process of corrosion was analyzed with a Scanning Electron Microscope (SEM) test. The changes in the hydration products were investigated through the X-ray diffraction (XRD) test and the Differential Scanning Calorimeter (DSC) test. Consequently, the degradation mechanisms of HECG in the case of different sodium sulfate solution concentrations and corrosion times were revealed. The results indicate that the corrosion of sodium sulfate and hydration exists simultaneously when the corrosion time is less than 7 days. When the corrosion time is 14 days, the hydration of HECG was complete. The main source of the early strength of HECG is that the C-S-H gel crosses and clings to form a solid and compact whole in three-dimensional space. The effect of Na₂SO₄ on the early strength formation of HECG is that the corrosion of Na₂SO₄ can postpone the conversion of CH crystal into C-S-H gel and damage the generated CH crystal. This study on the degradation mechanisms of HECG exposed to sodium sulfate corrosion can provide new ideas for sulfate resistance and durability design of HECG. Full article

(This article belongs to the Special Issue Advances in Methods for Performance Characterization and Prediction of Reinforced Concrete)

► Show Figures

Figure 1

16 pages, 2998 KiB

Open AccessArticle

Study on the Relationship between Early Shrinkage Cracking and Mechanical Properties of Nano-Clay Cement Mortar Based on Fractal Theory

by Shiyi Zhang, Zhisheng Fang, Wenjie Qi, Yingfang Fan and Surendra P. Shah

Buildings 2023, 13(1), 123; https://doi.org/10.3390/buildings13010123 - 03 Jan 2023

Cited by 9 | Viewed by 1413

Abstract

In order to study the influence of nano-clay on the crack resistance of cement-based materials, two kinds of nano-metakaolin (NMK) and two kinds of nano-attapulgite clay (NMA) were considered. The early cracking process and mechanical properties of nano-clay cement mortar (NCM) was studied [...] Read more.

In order to study the influence of nano-clay on the crack resistance of cement-based materials, two kinds of nano-metakaolin (NMK) and two kinds of nano-attapulgite clay (NMA) were considered. The early cracking process and mechanical properties of nano-clay cement mortar (NCM) was studied by using a plate knife-edge constraint test. Based on fractal theory, the distribution characteristics of NCM surface cracks were revealed, and the calculation method forNCM maximum crack width was given. The results show that the cracking time of the NMK-3 specimen is 2 and 6 h later than that of NMK-1 and NMA-2, respectively; the smaller the particle size of nano-clay, the earlier the cracking time of the specimen. However, nano-clay effectively inhibited the expansion of mortar cracks, and the cracks on the surface of NCM were thin and sparse. At 28 days, the maximum crack width of NMK-3 was 46.7% and 33.3% lower than that of NMK-1 and NMA-2, respectively. NMK hadthe best improvement effect on the mechanical properties cement mortar. The smaller the particle size, the more pronounced the improvement effect.The flexural strength ratio and compressive strength ratio at 7 and 28 days are 76.7%, 67.4%, and 61.2%, respectively.The distribution of surface cracks on NCM has fractal characteristics, and the fractal dimension of surface cracks is smaller than that of ordinary cement mortar. The larger the particle size of nano-clay, the smaller the fractal dimension of cracks. The quantitative relationship between fracture fractal dimension and NCM elastic modulus and shrinkage tensile stress is established. Full article

(This article belongs to the Special Issue Advances in Methods for Performance Characterization and Prediction of Reinforced Concrete)

► Show Figures

Figure 1

16 pages, 4494 KiB

Open AccessArticle

Study on the Relationship between Chloride Ion Penetration and Resistivity of NAC-Cement Concrete

by Xiaofei Liang, Wenjie Qi, Zhisheng Fang, Shiyi Zhang, Yingfang Fan and Surendra P. Shah

Buildings 2022, 12(12), 2044; https://doi.org/10.3390/buildings12122044 - 22 Nov 2022

Cited by 4 | Viewed by 1220

Abstract

To explore the effect of nano-attapulgite clay (NAC) on the durability of concrete, two kinds of NAC (calcined raw ore and calcined high viscosity ore: calcination at 650 °C for 2 h) were used to study their effects on the durability of concrete, [...] Read more.

To explore the effect of nano-attapulgite clay (NAC) on the durability of concrete, two kinds of NAC (calcined raw ore and calcined high viscosity ore: calcination at 650 °C for 2 h) were used to study their effects on the durability of concrete, mainly discussing the changes of chloride ion permeability and the resistivity of concrete with NAC. The effect of NAC on the strength of concrete was analyzed by testing the compressive strength of concrete. The two-electrode method, four-electrode method, and concrete resistivity tester were used to analyze the relationship between the testing method and concrete resistivity, and the effect of NAC on concrete resistivity was analyzed. The influence of NAC on the chloride corrosion resistance of concrete was analyzed by measuring the chloride diffusion coefficient, and the relationship between the chloride diffusion coefficient and resistivity was established. The diffusion process of chloride ions in concrete was analyzed by theoretical derivation and numerical simulation. The results show that: calcining raw ore NAC can improve the compressive strength of concrete, while calcining high-viscosity ore reduces the compressive strength of concrete. At the age of 28 days, the strength of concrete mixed with calcined raw ore is about 7.10% higher than that of ordinary concrete, while the compressive strength of concrete mixed with calcined high-viscosity ore is about 4.32% lower than that of common concrete. The resistivity of concrete mixed with calcined raw ore increases the fastest, and the 56 days age is about 15.8% and 29.6% higher than that of ordinary concrete and calcined high-viscosity ore. There is a good negative correlation between concrete resistivity and chloride diffusion coefficient. At 28 days, the incorporation of calcined raw ore concrete decreased by about 19.9% and 49.4% compared with ordinary concrete and calcined high-viscosity ore, respectively. After 10 years of decline, the chloride ion content is 11.1% and 23.2% lower than that of ordinary concrete and concrete mixed with calcined high viscosity ore. Full article

(This article belongs to the Special Issue Advances in Methods for Performance Characterization and Prediction of Reinforced Concrete)

► Show Figures

Figure 1

19 pages, 12668 KiB

Open AccessArticle

Study on Shrinkage Cracking Morphology of Cement Mortar with Different Nanoclay Particles under Restraint

by Guangying Liu, Shiyi Zhang, Yingfang Fan and Surendra P. Shah

Buildings 2022, 12(9), 1459; https://doi.org/10.3390/buildings12091459 - 15 Sep 2022

Cited by 3 | Viewed by 1188

Abstract

In this paper, different types and particle sizes of nanoclay (nano-metakaolin—NMK—and nano-attapulgite—NMA—clay) were selected to study the effect of nanoclay on the properties of cement-based cementitious materials. The stability of different nanoclay dispersions was analyzed. The effects of nanoclay on the mechanical properties [...] Read more.

In this paper, different types and particle sizes of nanoclay (nano-metakaolin—NMK—and nano-attapulgite—NMA—clay) were selected to study the effect of nanoclay on the properties of cement-based cementitious materials. The stability of different nanoclay dispersions was analyzed. The effects of nanoclay on the mechanical properties and cracking behavior of cement mortar were discussed. The crack propagation behavior of nanoclay cement mortar was analyzed by flat knife-edge induced constraint and ring constraint experiments. The research shows that the degree of aggregation of NMA particles is lower than that of NMK. The larger the particle size of NMA, the lower the degree of particle aggregation. The larger the particle size of NMK, the lower the degree of particle aggregation in water. NMK has the best improvement effect on cement mortar. The smaller the particle size, the more pronounced the improvement effect. The flexural strength ratio, compressive strength ratio, and elastic modulus ratio of 7 d and 28 d are 76.7%, 67.4%, and 61.2%, respectively. In the flat plate cracking experiment, the maximum crack width of NMK-3 and NMA-2 was reduced by 33.3% and 25.0%, respectively, compared with ordinary cement mortar. The maximum crack length was reduced by 55.1% and 33.1% compared with cement mortar. In the ring constraint experiment, the total cracked area of NMK-1, NMA-1, NMK-3, and NMA-2 rings increased by 64.3%, 45.0%, 92.7%, and 49.7%, respectively, compared with ordinary cement mortar rings after 60 days. NMK can advance the cracking time of cement mortar, but it can inhibit the generation and development of cracks and refine the crack width. Full article

(This article belongs to the Special Issue Advances in Methods for Performance Characterization and Prediction of Reinforced Concrete)

► Show Figures

Figure 1

20 pages, 6062 KiB

Open AccessArticle

Study on Deformation Characteristics and Damage Model of NMK Concrete under Cold Environment

by Shiyi Zhang, Yingfang Fan and Surendra P. Shah

Buildings 2022, 12(9), 1431; https://doi.org/10.3390/buildings12091431 - 12 Sep 2022

Cited by 4 | Viewed by 1302

Abstract

To improve the ability of concrete structures to resist freeze-thaw damage in cold environments, explore the effect and mechanism of nano-metakaolin (NMK) on frost resistance of concrete. And make up for the deficiencies in the mechanical properties and deformation process of na-no-metakaolin concrete [...] Read more.

To improve the ability of concrete structures to resist freeze-thaw damage in cold environments, explore the effect and mechanism of nano-metakaolin (NMK) on frost resistance of concrete. And make up for the deficiencies in the mechanical properties and deformation process of na-no-metakaolin concrete in freeze-thaw environments. Rapid freeze-thaw cycle experiment was car-ried out to detect the deterioration law of concrete. Physical and mechanical properties under freeze-thaw environment was measured. The modification mechanism of nano-metakaolin on con-crete frost resistance from micro and meso scales was analyzed. The effect of freeze-thaw damage on nano-metakaolin concrete was characterized. The influence law of stress strain is established, and the meso-statistical damage constitutive model of nano-metakaolin concrete under freeze-thaw action is established. The results show that: Compared with other nano-clays, adding 5% nano-metakaolin can effectively slow down concrete’s freeze-thaw cracking and crack propagation. After 125 freeze-thaw cycles, the surface crack width of concrete mixed with 5% nano-metakaolin is only 0.1mm. Without freeze-thaw cycles, the compressive strength of concrete mixed with 3% nano-metakaolin is the highest, which is 28.75% higher than that of ordinary concrete; after 125 freeze-thaw cycles, the loss rate of compressive strength of concrete mixed with 5% nano-metakaolin was 12.07%. After 125 freeze-thaw cycles, the peak strain is 0.45 times that of concrete without NMK, and the peak stress is 3 times that of concrete without NMK. Full article

(This article belongs to the Special Issue Advances in Methods for Performance Characterization and Prediction of Reinforced Concrete)

► Show Figures

Figure 1

13 pages, 4868 KiB

Open AccessArticle

Effect Mechanisms of Toner and Nano-SiO₂ on Early Strength of Cement Grouting Materials for Repair of Reinforced Concrete

by Zedong Zhao, Jingchun Chen, Jian Wang, Shenghan Zhuang, Haiwei Chen, Hongbo Zhao, Chunguang Wang, Lin Zhang, Min Li, Gen Li and Jiaolong Ren

Buildings 2022, 12(9), 1320; https://doi.org/10.3390/buildings12091320 - 28 Aug 2022

Cited by 4 | Viewed by 1429

Abstract

The reinforced concrete invariably involves some diseases (e.g., crack, void, etc.) due to the complex service conditions. These diseases are usually repaired to extend the service life of reinforced concrete by using cement grouting materials. In order to meet a certain color need [...] Read more.

The reinforced concrete invariably involves some diseases (e.g., crack, void, etc.) due to the complex service conditions. These diseases are usually repaired to extend the service life of reinforced concrete by using cement grouting materials. In order to meet a certain color need of reinforced concrete, toner is mixed into the cement grouting materials. However, the toner has a negative effect on the early strength of cement grouting materials. Unfortunately, the mechanism of the negative effects of toner is still unclear, and no effective and targeted measures have been put forward. Hence, the main work of this paper reveals the mechanisms of the toner and nano-SiO₂ (N-S) in the hydration process and the strength generation of the cement grouting materials in the case of different curing ages and nano-SiO₂ contents via the scanning electron microscopy test (SEM), X-ray diffraction test (XRD), differential scanning calorimetry test (DSC), and Fourier transform infrared spectroscopy test (FTRI). Results show that: (a) the toner hinders the generation of AFt and CH crystals (especially for 1-day and 3-day), which delays the hydration process and weakens the early performance of cement grouting materials; (b) the N-S promotes the hydration process and the formation of C-S-H gels, so as to effectively increasing the early strength and reducing (but not eliminate) the adverse effect of toner on cement grouting materials; (c) With the increase of every 1% N-S, the flexural strength of 1-day, 3-day, and 7-day average increased by 11.3%, 2.9%, and 0.9%, respectively, and the compressive strength of 1-day, 3-day, and 7-day average increased by 0.8%, 0.3%, and 0.1%. Full article

(This article belongs to the Special Issue Advances in Methods for Performance Characterization and Prediction of Reinforced Concrete)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Advances in Methods for Performance Characterization and Prediction of Reinforced Concrete

Share This Special Issue

Special Issue Editors

Special Issue Information

Published Papers (10 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI