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Keywords = chloride ion permeability coefficient

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21 pages, 13539 KiB  
Article
Impact of Fiber Type on Chloride Ingress in Concrete: A MacroXRF Imaging Analysis
by Suânia Fabiele Moitinho da Silva, Wanderson Santos de Jesus, Thalles Murilo Santos de Almeida, Renato Quinto de Oliveira Novais, Laio Andrade Sacramento, Joaquim Teixeira de Assis, Marcelino José dos Anjos and José Renato de Castro Pessôa
Appl. Sci. 2025, 15(15), 8495; https://doi.org/10.3390/app15158495 (registering DOI) - 31 Jul 2025
Viewed by 85
Abstract
Chloride ion penetration is one of the most aggressive threats to reinforced concrete, as it triggers the electrochemical corrosion of steel reinforcement, compromising structural integrity and durability. Chloride ingress occurs through the porous structure of concrete, making permeability control crucial for enhancing structural [...] Read more.
Chloride ion penetration is one of the most aggressive threats to reinforced concrete, as it triggers the electrochemical corrosion of steel reinforcement, compromising structural integrity and durability. Chloride ingress occurs through the porous structure of concrete, making permeability control crucial for enhancing structural longevity. Fiber-reinforced concrete (FRC) is widely used to improve durability; however, the effects of different fiber types on chloride resistance remain unclear. This study examines the influence of glass and polypropylene fibers on concrete’s microstructure and chloride penetration resistance. Cylindrical specimens were prepared, including a reference mix without fibers and mixes with 0.25% and 0.50% fiber content by volume. Both fiber types were tested for chloride resistance. The accelerated non-steady-state migration method was employed to determine the resistance coefficients to chloride ion penetration, while X-ray macrofluorescence (MacroXRF) mapped the chlorine infiltration depth in the samples. Compressive strength decreased in all fiber-reinforced samples, with 0.50% glass fiber leading to a 56% reduction in strength. Nevertheless, the XRF results showed that a 0.25% fiber content significantly reduced chloride penetration, with polypropylene fibers outperforming glass fibers. These findings highlight the critical role of fiber type and volume in improving concrete durability, offering insights for designing long-lasting FRC structures in chloride-rich environments. Full article
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15 pages, 2001 KiB  
Article
Study on the Impact of Lithium Slag as an Alternative to Washed Sand on Mortar Properties
by Xianliang Zhou, Wei Dai, Xi Zhu and Xiaojun Zhou
Materials 2025, 18(15), 3490; https://doi.org/10.3390/ma18153490 - 25 Jul 2025
Viewed by 226
Abstract
Lithium slag (LS), a by-product of lithium extraction processes, poses a significant disposal challenge during the rapid development of new energy technologies. In this study, LS was used to replace partially washed sand in the process of mortar production to compensate for the [...] Read more.
Lithium slag (LS), a by-product of lithium extraction processes, poses a significant disposal challenge during the rapid development of new energy technologies. In this study, LS was used to replace partially washed sand in the process of mortar production to compensate for the content of stone powder in sand. Five mortar mixes containing varying proportions of LS were prepared, and the macroscopic performance was evaluated. A comprehensive microscopic analysis, including microstructure observations, hydration product identification, and pore structure analysis, was conducted. The impact of LS on the chloride ion permeability of mortar was also investigated in this study. The results indicate that an increase in LS content gradually reduces the workability of the mortar, with a 39.29% decrease in fluidity when 40% of the sand is replaced with LS. Moreover, the compressive and flexural strengths of the mortar initially increase and then decrease with higher LS content. Microscopic tests reveal that 20% LS substitution significantly optimizes the pore structure of the mortar, resulting in a lower chloride ion permeability coefficient. Consequently, 20% LS substitution is recommended as the optimal dosage for use as fine aggregate in mortar. Full article
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15 pages, 4450 KiB  
Article
Effect of Nano-SiO2 on the Hydration, Microstructure, and Mechanical Performances of Solid Waste-Based Cementitious Materials
by Zian Geng, Yu Zhang, Yiwen Zhou, Jiapeng Duan and Zhuqing Yu
Materials 2025, 18(11), 2636; https://doi.org/10.3390/ma18112636 - 4 Jun 2025
Viewed by 441
Abstract
Solid waste-based cementitious materials (SWBC) are composed of steel slag (SS), granulated blast furnace slag (GBFS), fly ash (FA), desulfurization gypsum (DG), and Portland cement (PC). Currently, SWBC holds great potential as a sustainable building material; however, its low early compressive strength and [...] Read more.
Solid waste-based cementitious materials (SWBC) are composed of steel slag (SS), granulated blast furnace slag (GBFS), fly ash (FA), desulfurization gypsum (DG), and Portland cement (PC). Currently, SWBC holds great potential as a sustainable building material; however, its low early compressive strength and volume expansion limit its range of application. Therefore, the main objective of this study is to enhance the mechanical properties and dimensional stability of SWBC by adding nano-SiO2, while also improving its resistance to chloride ions, thereby promoting its use in the field of sustainable building materials. A comprehensive experimental approach integrating mechanical performance testing, shrinkage analysis, and chloride diffusion coefficient evaluation was established, with the testing methods of thermogravimetric analysis-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The study found that adding nano-SiO2 enhanced the nucleation of calcium silicate hydrates (C-S-H) gel in hydrated SWBC, leading to improved compressive strength and reduced chloride permeability when SiO2 addition was 0.5%. When the hydration period extends to 28 days, the modified SWBC achieves a compressive strength of 56 MPa. However, excessive nano-SiO2 (≥1%) inhibited the long-term hydration of SWBC but had no significant effect on the final compressive strength. Full article
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14 pages, 8206 KiB  
Article
Mechanical, Chloride Resistance, and Microstructural Properties of Basalt Fiber-Reinforced Fly Ash–Silica Fume Composite Concrete
by Yishan Li, Yan Liu and Wei Zhang
Minerals 2025, 15(4), 348; https://doi.org/10.3390/min15040348 - 27 Mar 2025
Cited by 1 | Viewed by 393
Abstract
Basalt fiber has advantages in enhancing the mechanical properties of concrete, but the comprehensive effects of fiber content and length, as well as the relationship between mechanical and impermeability performance, remain unclear and require systematic verification. This study aims to quantify the effects [...] Read more.
Basalt fiber has advantages in enhancing the mechanical properties of concrete, but the comprehensive effects of fiber content and length, as well as the relationship between mechanical and impermeability performance, remain unclear and require systematic verification. This study aims to quantify the effects of basalt fiber content and length on mechanical properties (compressive strength, tensile strength, and flexural strength) and concrete permeability performance and reveal the underlying mechanisms. The macroscopic performance results indicate the following: (1) the optimum fiber content of compressive strength and flexural strength of basalt fiber-reinforced concrete is 1.5 kg/m3; (2) the optimum content of tensile strength is 1.0 kg/m3; and (3) the impermeability performance of the fiber-reinforced concrete is most significantly improved when the fiber content reaches 1.0 kg/m3 and the fiber length is 18 mm. During the permeability tests, a nonlinear functional relationship exists between two indicators, electric flux and chloride ion migration coefficient. Microscopic analysis showed that mineral admixtures (fly ash and silica fume) promoted the secondary hydration reaction in the cementitious material, generating a significant amount of C-(A)-S-H gels to increase the density of the concrete matrix. After incorporating basalt fibers, they tightly envelop the concrete matrix, reducing the number of internal voids and achieving a synergistic stress-bearing effect with the concrete, confirming that the addition of fibers optimizes the mechanical and impermeability properties of the concrete. This study provides a quantitative reference for the basalt fiber reinforcement design of engineering concrete structures and helps extend the service life of concrete buildings. Full article
(This article belongs to the Special Issue Recycling and Utilization of Metallurgical and Chemical Solid Waste)
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16 pages, 16283 KiB  
Article
Impermeability, Strength and Microstructure of Concrete Modified by Nano-Silica and Expansive Agent
by Pinmo Zeng, Mohammed A. A. M. Abbas, Xinyi Ran and Peipeng Li
J. Compos. Sci. 2025, 9(3), 108; https://doi.org/10.3390/jcs9030108 - 25 Feb 2025
Cited by 1 | Viewed by 820
Abstract
The impermeability of concrete is very important to its durability and service life, which could be affected by nanomaterial and mineral admixture additions. This paper tends to enhance the impermeability, strength, and microstructure of concrete using nano-silica (NS) and U-type expansive agent (UEA). [...] Read more.
The impermeability of concrete is very important to its durability and service life, which could be affected by nanomaterial and mineral admixture additions. This paper tends to enhance the impermeability, strength, and microstructure of concrete using nano-silica (NS) and U-type expansive agent (UEA). The slump flow, compressive strength, chloride ion resistance, water penetration and absorption, hydration, and microstructure of concrete are investigated under different NS and UEA contents. The results indicate that an appropriate NS content of 2% contributes to dense pore structure and the generation of more hydration product for impermeability-enhanced concrete, which results in a compressive strength of 43.53 MPa and chloride ion and water penetration resistance improvements of 21% and 35%, respectively. The slump flow and compressive strength of concrete decrease slightly in the presence of UEA utilization, while the chloride ion and water penetration resistances are firstly enhanced and then weakened with the increase in UEA contents. In the case of 9% UEA, the concrete achieves a compressive strength of 31.54 MPa, a chloride ion penetration coefficient of 9.34 × 10−12 m2/s, and a relative permeability coefficient of 2.56 cm/s. Full article
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16 pages, 5753 KiB  
Article
Effect of Macro Fibers on Chloride Permeability and Damage of Concrete Under Uniaxial Compression
by Zengyao Li, Yongqiang Yang, Yihan Wang, Wenqiang Wang and Bailin Zhang
Materials 2025, 18(4), 784; https://doi.org/10.3390/ma18040784 - 11 Feb 2025
Cited by 3 | Viewed by 469
Abstract
In many offshore structures, structural components are often subjected to compressive forces and seawater corrosion. Therefore, understanding their resistance to chloride ion-induced corrosion under compression is crucial. This study investigates the effects of macro polypropylene fibers and macro steel fibers on the chloride [...] Read more.
In many offshore structures, structural components are often subjected to compressive forces and seawater corrosion. Therefore, understanding their resistance to chloride ion-induced corrosion under compression is crucial. This study investigates the effects of macro polypropylene fibers and macro steel fibers on the chloride permeability and damage of concrete under uniaxial compression. Ultrasonic testing is performed before and after the uniaxial compression test to assess the damage to concrete specimens at different stress levels. Simultaneously, the Rapid Chloride Migration test is conducted on the specimens subjected to various compressive stress levels. The results reveal that the chloride permeability of concrete is influenced by the stress level after uniaxial compression. Additionally, a threshold phenomenon is observed in the chloride permeability: after reaching the threshold stress level, the chloride diffusion coefficient increases significantly. Compared with plain concrete, incorporating macro fibers raises the threshold stress level for chloride ion penetration. Furthermore, this threshold stress level increases with higher fiber content. The variation in ultrasonic velocity with stress level is also found to be an effective indicator for evaluating the chloride permeability of concrete under uniaxial compression. Moreover, a prediction model for the chloride permeability of FRC (fiber reinforced concrete) is proposed based on the results. Full article
(This article belongs to the Section Construction and Building Materials)
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33 pages, 7791 KiB  
Article
Durable Structural Recycled Concrete for Different Exposure Environments
by Carla Vintimilla and Miren Etxeberria
Materials 2025, 18(3), 587; https://doi.org/10.3390/ma18030587 - 28 Jan 2025
Cited by 1 | Viewed by 803
Abstract
In this work, the influence of limited percentages of coarse (CRCA) and fine (FRCA) recycled concrete aggregates (Type A recycled aggregates) on the durability properties of structural concrete was analyzed. Concretes were designed using 50% and 60% CRCA with simultaneous additions of 0%, [...] Read more.
In this work, the influence of limited percentages of coarse (CRCA) and fine (FRCA) recycled concrete aggregates (Type A recycled aggregates) on the durability properties of structural concrete was analyzed. Concretes were designed using 50% and 60% CRCA with simultaneous additions of 0%, 10%, and 20% FRCA and different types of cement (CEM II/AL 42.5 R, CEM II/AS 42.5 N/SRC, and CEM III/B 42.5 N-LH/SR). Recycled aggregate concrete (RAC) and natural aggregate concrete (NAC) mixtures were produced with similar compressive strength using effective water–cement ratios of 0.47 and 0.5. The drying shrinkage values and durability properties were determined, and they included the chloride permeability, chloride penetration depth, and accelerated and natural carbonation rates. The findings revealed that RAC produced using CEM III/B, which included the mixture produced with 60% coarse RCA and 20% fine RCA, achieved low chloride ion penetrability (up to 850 Coulombs) and exhibited the lowest chloride diffusion coefficient, approximately 7 × 10−13. Additionally, the RAC-C60-F20 concretes made with CEM II/AS proved suitable for the XC3 and XC4 exposure environments, guaranteeing a lifespan of 50 and 100 years based on the natural carbonation rate. In addition, the RAC-C60-F20 concrete made with CEM II/AL cement exhibited an adequate natural carbonation rate for XC4 environments, which was between 1.6 and 2.4 units higher than the accelerated carbonation rate. This work validates the use of RAC in XC environments (corrosion induced by carbonation) and XS1 environments (corrosion caused by chlorides from seawater). Full article
(This article belongs to the Special Issue Special Functional and Environmental Cement-Based Materials)
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25 pages, 9963 KiB  
Article
Study on the Influence of Thermoplastic Microcapsules on the Sulfate Resistance and Self-Healing Performance of Limestone Calcined Clay Cement Concrete
by Wei Du, Lu Jiang, Quantao Liu, Wei Chen and Qingjun Ding
Molecules 2024, 29(20), 4797; https://doi.org/10.3390/molecules29204797 - 10 Oct 2024
Cited by 3 | Viewed by 1322
Abstract
Limestone calcined clay cement (LC3), enhanced through reactions with volcanic ash and the interaction between limestone and clay, significantly improves the performance of cementitious materials. It has the potential to cut CO2 emissions by up to 30% and energy consumption in cement [...] Read more.
Limestone calcined clay cement (LC3), enhanced through reactions with volcanic ash and the interaction between limestone and clay, significantly improves the performance of cementitious materials. It has the potential to cut CO2 emissions by up to 30% and energy consumption in cement manufacture by 15% to 20%, providing a promising prospect for the large-scale production of low-carbon cement with a lower environmental effect. To effectively manufacture LC3 concrete, this study utilized limestone (15%), calcined clay (30%), and gypsum (5%) as supplementary cementitious materials (SCMs), replacing 50% of ordinary Portland cement (OPC). However, in regions abundant in sulfate, sulfate attack can cause interior cracking of concrete, reducing the longevity of the building. To address this issue, microcapsules containing microcrystalline wax, ceresine wax, and nano-CaCO3 encapsulated in epoxy resin were prepared and successfully incorporated into LC3 concrete. Sulfate resistance tests were conducted through sulfate dry–wet cycles, comparing samples with and without microcapsules. The findings revealed that the initial mechanical and permeability properties of LC3 concrete did not significantly differ from OPC concrete. LC3 concrete with added microcapsules (SP4) exhibited enhanced resistance to sulfate attack, reducing mass loss and compressive strength degradation. SEM images displayed a mesh-like structure of repair products in SP4. After 14 days of self-repair, SP4 exhibited a 44.2% harmful pore ratio, 98.1% compressive strength retention, 88.7% chloride ion diffusion coefficient retention, 91.12 mV maximum amplitude, and 9.14 mV maximum frequency amplitude. The experimental results indicate that the presence of microcapsules enhances the sulfate attack self-healing performance of LC3 concrete. Full article
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20 pages, 2797 KiB  
Review
A Review of Gene–Property Mapping of Cementitious Materials from the Perspective of Material Genome Approach
by Fei Li and Yan Zhong
Materials 2024, 17(15), 3640; https://doi.org/10.3390/ma17153640 - 23 Jul 2024
Cited by 1 | Viewed by 1132
Abstract
As an important gelling material, cementitious materials are widely used in civil engineering construction. Currently, research on these materials is conducted using experimental and numerical image processing methods, which enable the observation and analysis of structural changes and mechanical properties. These methods are [...] Read more.
As an important gelling material, cementitious materials are widely used in civil engineering construction. Currently, research on these materials is conducted using experimental and numerical image processing methods, which enable the observation and analysis of structural changes and mechanical properties. These methods are instrumental in designing cementitious materials with specific performance criteria, despite their resource-intensive nature. The material genome approach represents a novel trend in material research and development. The establishment of a material gene database facilitates the rapid and precise determination of relationships between characteristic genes and performance, enabling the bidirectional design of cementitious materials’ composition and properties. This paper reviews the characteristic genes of cementitious materials from nano-, micro-, and macro-scale perspectives. It summarizes the characteristic genes, analyzes expression parameters at various scales, and concludes regarding their relationship to mechanical properties. On the nanoscale, calcium hydrated silicate (C-S-H) is identified as the most important characteristic gene, with the calcium–silicon ratio being the key parameter describing its structure. On the microscale, the pore structure and bubble system are key characteristics, with parameters such as porosity, pore size distribution, pore shape, air content, and the bubble spacing coefficient directly affecting properties like frost resistance, permeability, and compressive strength. On the macroscale, the aggregate emerges as the most important component of cementitious materials. Its shape, angularity, surface texture (grain), crushing index, and water absorption are the main characteristics influencing properties such as chloride ion penetration resistance, viscosity, fluidity, and strength. By analyzing and mapping the relationship between these genes and properties across different scales, this paper offers new insights and establishes a reference framework for the targeted design of cementitious material properties. Full article
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18 pages, 1207 KiB  
Review
Factors Influencing Chloride Ion Diffusion in Reinforced Concrete Structures
by Qiulang Xu, Bin Liu, Lin Dai, Maogui Yao and Xijun Pang
Materials 2024, 17(13), 3296; https://doi.org/10.3390/ma17133296 - 4 Jul 2024
Cited by 6 | Viewed by 3050
Abstract
Reinforced concrete structures are prone to the corrosion of steel bars when exposed to chloride-rich environments, which can severely impact their durability. To address this issue, a comprehensive understanding of the factors influencing chloride ion diffusion in concrete is essential. This paper provides [...] Read more.
Reinforced concrete structures are prone to the corrosion of steel bars when exposed to chloride-rich environments, which can severely impact their durability. To address this issue, a comprehensive understanding of the factors influencing chloride ion diffusion in concrete is essential. This paper provides a summary of recent domestic and foreign research on chloride ion transport in concrete, focusing on six key factors: water–binder ratio, additive content, crack width, ambient temperature, relative humidity, and dry–wet cycles. The findings show that the diffusion coefficient of chloride ions in concrete increases with a higher water–binder ratio and decreases with increased additive content. Additionally, wider cracks result in a greater diffusion of chloride ions. The permeability resistance of concrete to chloride ions decreases with rising temperature and humidity, and dry–wet cycles further accelerate the diffusion of chloride ions. The article concludes by discussing various anti-corrosion measures, such as the use of corrosion inhibitors, surface coatings, and electrochemical treatments, to ensure the longevity of the structure. Finally, directions for future research are proposed. Full article
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13 pages, 2140 KiB  
Article
The Influence of CO2 Curing on the Properties of Coal Gangue Non-Fired Blocks
by Bing Sun and Hui Wang
Buildings 2024, 14(7), 1950; https://doi.org/10.3390/buildings14071950 - 27 Jun 2024
Cited by 1 | Viewed by 784
Abstract
Coal gangue is a solid waste, which can cause serious pollution of the atmosphere and water sources due to its long-term accumulation. In this article, the influence of CO2-cured coal gangue on the slump flow, the mechanical strengths, the thermal conductivity [...] Read more.
Coal gangue is a solid waste, which can cause serious pollution of the atmosphere and water sources due to its long-term accumulation. In this article, the influence of CO2-cured coal gangue on the slump flow, the mechanical strengths, the thermal conductivity coefficient, the chloride ion permeability, the water resistance coefficient and the leached Pb of the coal-gangue-block masonry are determined. Moreover, the temperature distributions at different measuring points of a coal-gangue-block cabin model are obtained. The results exhibit that CO2-cured gangue demonstrates positive effects on the slump flow, the mechanical strengths and the thermal conductivity coefficient, with the slump flow rates increasing by 0%~23.6%, the mechanical strength rates increasing by 0%~222.7% and the thermal conductivity coefficient rates increasing by 0%~73.2%. Straw fibers increase mechanical strengths and decrease thermal conductivity at rates of 0%~222.7% and 0%~32.6%. Foam decreases the mechanical strengths and the thermal conductivity coefficient by 0%~71.2% and 0%~87.1%. The chloride ion migration coefficients are decreased by 0%~42.1% and 0%~43.7% with the added CO2-cured coal gangue and the straw fibers. The added foam leads to an increase in the chloride ion migration coefficient of 0%~73.2%. The foam and the straw fibers show delaying temperature changes in a coal-gangue-block cabin model, while when CO2-cured coal gangue is added, the effect is the opposite. The CO2-cured coal gangue and the straw fibers lead to decreases in the leached Pb and Zn, while when the foam’s mass ratio increases, the result is the contrary. Full article
(This article belongs to the Section Building Materials, and Repair & Renovation)
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19 pages, 11734 KiB  
Article
Effect of Micro-Cracks on Chloride Ion Diffusion in Concrete Based on Stochastic Aggregate Approach
by Qianfan Yang, Yuching Wu, Peng Zhi and Peng Zhu
Buildings 2024, 14(5), 1353; https://doi.org/10.3390/buildings14051353 - 9 May 2024
Cited by 2 | Viewed by 1194
Abstract
For concrete structures in offshore areas, chloride ion erosion is one of the main factors affecting durability. It is crucial to evaluate the chloride ion permeability resistance of concrete structures. In this paper, a finite element simulation of the chloride ion diffusion process [...] Read more.
For concrete structures in offshore areas, chloride ion erosion is one of the main factors affecting durability. It is crucial to evaluate the chloride ion permeability resistance of concrete structures. In this paper, a finite element simulation of the chloride ion diffusion process in concrete is conducted. A mass diffusion finite element model based on a random aggregate approach is established to investigate the influences of an aggregate, the interface transition zone, and micro-cracks on the chloride ion diffusion coefficients in concrete. The results show that the mass diffusion finite element analysis based on the exponential function model and the power function model can effectively simulate the chloride ion diffusion process in concrete. In addition, the data reveal that volume fraction and distribution aggregates considerably affect chloride ion diffusivity in concrete. Also, the interface transition zone significantly accelerates chloride ion diffusion in concrete. Moreover, this acceleration effect exceeds the barrier effect of an aggregate. Full article
(This article belongs to the Special Issue Low-Carbon Concrete with Different Sources of Solid Waste)
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20 pages, 6750 KiB  
Article
Enhancing Volumetric Stability of Metakaolin-Based Geopolymer Composites with Organic Modifiers WER and SCA
by Mo Zhang, Yongquan Zang and Lingyan Shan
Buildings 2024, 14(3), 586; https://doi.org/10.3390/buildings14030586 - 22 Feb 2024
Cited by 3 | Viewed by 1603
Abstract
Shrinkage during hardening and curing is one of the largest challenges for the widespread application of metakaolin-based geopolymers (MKGs). To solve this problem, a silane coupling agent (SCA) and waterborne epoxy resin (WER) were used to synthesize MKG composites. The individual and synergistic [...] Read more.
Shrinkage during hardening and curing is one of the largest challenges for the widespread application of metakaolin-based geopolymers (MKGs). To solve this problem, a silane coupling agent (SCA) and waterborne epoxy resin (WER) were used to synthesize MKG composites. The individual and synergistic effects of the SCA and WER on chemical, autogenous, and drying shrinkage were assessed, the modification mechanisms were investigated by microstructural characterization, and shrinkage resistance was evaluated by the chloride ion permeability of MKG composite coatings. The results showed that the SCA and WER significantly decreased the chemical shrinkage, autogenous shrinkage, and drying shrinkage of the MKG, with the highest reductions of 46.4%, 131.2%, and 25.2% obtained by the combination of 20 wt% WER and 1 wt% SCA. The incorporation of the organic modifiers densified the microstructure. Compared with the MKG, the total volume of mesopores and macropores in MKG-WER, MKG-SCA, and MKG-WER-SCA decreased by 11.5%, 8.7%, and 3.8%, respectively. In particular, the silanol hydrolyzed from the SCA can react with the opened epoxy ring of the WER and the aluminosilicate oligomers simultaneously to form a compact network and resist shrinkage during the hardening and continuous reaction of the geopolymer. Furthermore, the apparently lowered chloride ion diffusion coefficient of concrete (i.e., reduction of 51.4% to 59.5%) by the WER- and SCA-modified MKG coatings verified their improved shrinkage resistance. The findings in this study provide promising methods to essentially solve the shrinkage problem of MKGs at the microscale and shed light on the modification mechanism by WERs and SCAs, and they also suggest the applicability of MKG composites in protective coatings for marine concrete. Full article
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13 pages, 1561 KiB  
Article
Research on the Strength Damage and Permeability Characteristics of Cemented Paste Backfill under Chlorine Salt Erosion and Dry–Wet Cycles
by Hao Li, Hongjiang Wang and Longjian Bai
Minerals 2024, 14(2), 177; https://doi.org/10.3390/min14020177 - 6 Feb 2024
Cited by 6 | Viewed by 1395
Abstract
Cement paste backfill (CPB) suffers serious damage and deterioration under the dual erosion conditions of the dry–wet cycle caused by the high chloride salt concentration in mine water and the fluctuation of mine water level. In order to discuss the mechanical properties and [...] Read more.
Cement paste backfill (CPB) suffers serious damage and deterioration under the dual erosion conditions of the dry–wet cycle caused by the high chloride salt concentration in mine water and the fluctuation of mine water level. In order to discuss the mechanical properties and permeability characteristics of CPB under erosion, this study designs an immersion experiment for CPB under chloride salt and dry–wet cycle conditions. Through a uniaxial compressive strength (UCS) test, the change law for the mechanical parameters of the CPB was investigated, the strength constitutive equation of the CPB was constructed and the deterioration process of the CPB was analyzed. The penetration test was used to investigate the diffusion characteristics of the packing under chloride salt and dry–wet cycle conditions. The results showed that the strength and Young’s modulus of the CPB initially increased and then rapidly decreased, with maximum decrease rates of 32.2% and 38.2%, respectively. The CPB structure exhibits an initial undamaged stage, an initial damaged stage, a damaged development stage, a damaged destruction stage and a residual damaged stage. The chloride ion penetration depth gradually increased with the number of dry–wet cycles, with a maximum diffusion depth of 20.5 mm. The maximum apparent diffusion coefficient of chloride ion was 18.99 × 10−10 m2/s, and the maximum concentration was 0.303 mol/L. Under the double erosion conditions of chloride salt and dry–wet cycle, the CPB structure was severely damaged. Full article
(This article belongs to the Section Clays and Engineered Mineral Materials)
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17 pages, 26645 KiB  
Article
Preparation and Performance Study of High-Strength and Corrosion-Resistant Cement-Based Materials Applied in Coastal Acid Rain Areas
by Junfeng Wang, Shaoxuan Zhang, Qionglin Fu, Yang Hu, Liulei Lu and Zhihao Wang
Materials 2024, 17(3), 752; https://doi.org/10.3390/ma17030752 - 4 Feb 2024
Cited by 2 | Viewed by 1719
Abstract
Investigations regarding the preparation and durability of cement-based materials applied in specific coastal acid rain environments are scarce, particularly those involving the addition of four auxiliary cementitious materials (ACMs) to cement for modification. To improve the durability of concrete structures in coastal acid [...] Read more.
Investigations regarding the preparation and durability of cement-based materials applied in specific coastal acid rain environments are scarce, particularly those involving the addition of four auxiliary cementitious materials (ACMs) to cement for modification. To improve the durability of concrete structures in coastal acid rain areas, a systematic study was conducted regarding the preparation of high-strength and corrosion-resistant cement-based materials using ACM systems composed of fly ash (FA), granulated blast furnace slag (GBFS), silica fume (SF), and desulfurization gypsum (DG) instead of partial cement. Through an orthogonal experimental design, the effect of the water–binder ratio, cementitious ratio, and replacement cement ratio on the compressive strength, corrosion resistance coefficient, and chloride ion permeability coefficient of the materials were analyzed and the mix proportions of the materials were evaluated and optimized using the comprehensive scoring method. The results show that implementing a FA:GBFS:SF:DG ratio of 2:6:1:1 to replace 60% of cement allows the consumption of calcium hydroxide crystals generated through cement hydration, promotes the formation of ettringite, optimizes the pore structures of cementitious materials, and improves the compressive strength, acid corrosion resistance, and chloride ion permeability of the materials. This study provides a reference for selecting concrete materials for buildings in coastal acid rain environments. Full article
(This article belongs to the Section Construction and Building Materials)
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