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Keywords = chemical sulfate attack

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31 pages, 8031 KiB  
Article
Study on the Mechanical Properties of Coal Gangue Materials Used in Coal Mine Underground Assembled Pavement
by Jiang Xiao, Yulin Wang, Tongxiaoyu Wang, Yujiang Liu, Yihui Wang and Boyuan Zhang
Appl. Sci. 2025, 15(15), 8180; https://doi.org/10.3390/app15158180 - 23 Jul 2025
Viewed by 194
Abstract
To address the limitations of traditional hardened concrete road surfaces in coal mine tunnels, which are prone to damage and entail high maintenance costs, this study proposes using modular concrete blocks composed of fly ash and coal gangue as an alternative to conventional [...] Read more.
To address the limitations of traditional hardened concrete road surfaces in coal mine tunnels, which are prone to damage and entail high maintenance costs, this study proposes using modular concrete blocks composed of fly ash and coal gangue as an alternative to conventional materials. These blocks offer advantages including ease of construction and rapid, straightforward maintenance, while also facilitating the reuse of substantial quantities of solid waste, thereby mitigating resource wastage and environmental pollution. Initially, the mineral composition of the raw materials was analyzed, confirming that although the physical and chemical properties of Liangshui Well coal gangue are slightly inferior to those of natural crushed stone, they still meet the criteria for use as concrete aggregate. For concrete blocks incorporating 20% fly ash, the steam curing process was optimized with a recommended static curing period of 16–24 h, a temperature ramp-up rate of 20 °C/h, and a constant temperature of 50 °C maintained for 24 h to ensure optimal performance. Orthogonal experimental analysis revealed that fly ash content exerted the greatest influence on the compressive strength of concrete, followed by the additional water content, whereas the aggregate particle size had a comparatively minor effect. The optimal mix proportion was identified as 20% fly ash content, a maximum aggregate size of 20 mm, and an additional water content of 70%. Performance testing indicated that the fabricated blocks exhibited a compressive strength of 32.1 MPa and a tensile strength of 2.93 MPa, with strong resistance to hydrolysis and sulfate attack, rendering them suitable for deployment in weakly alkaline underground environments. Considering the site-specific conditions of the Liangshuijing coal mine, ANSYS 2020 was employed to simulate and analyze the mechanical behavior of the blocks under varying loads, thicknesses, and dynamic conditions. The findings suggest that hexagonal coal gangue blocks with a side length of 20 cm and a thickness of 16 cm meet the structural requirements of most underground mine tunnels, offering a reference model for cost-effective paving and efficient roadway maintenance in coal mines. Full article
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19 pages, 5279 KiB  
Article
Methods for Quantitative Determination of Iron Sulfides in Rocks
by Zhixin Wang, Shaoping Wang, Wei Li, Bing Cao, Xiaojun Huang, Xin Chuai, Xinyu Zhang and Min Deng
Materials 2025, 18(11), 2647; https://doi.org/10.3390/ma18112647 - 5 Jun 2025
Viewed by 413
Abstract
When iron sulfides are used as aggregate in concrete production, it easily oxidizes to form harmful substances such as sulfates. This results in acid corrosion and internal sulfate attack (ISA), significantly reducing concrete durability. To date, the quantification methods for iron sulfides in [...] Read more.
When iron sulfides are used as aggregate in concrete production, it easily oxidizes to form harmful substances such as sulfates. This results in acid corrosion and internal sulfate attack (ISA), significantly reducing concrete durability. To date, the quantification methods for iron sulfides in aggregates remain inaccurate, often neglecting pyrrhotite (a type of iron sulfide). No standardized methods or threshold values for the sulfide content in aggregates have been established, nor have technical guidelines for the application of sulfide-containing aggregates, limiting their use. This study proposes an on-site quantification procedure for determining the pyrite and pyrrhotite content in tailings using a selective chemical dissolution process. An orthogonal experiment was designed to determine the optimal dissolution conditions by considering four factors: particle size, reaction temperature, acid concentration, and reaction time. The pyrrhotite quantification method showed a relative standard deviation (RSD) of 3.60% (<5%) and a mean relative error of 3.19% (<5%), while the pyrite quantification method showed an RSD of 3.11% (<5%) with a mean relative error of 4.70% (<5%). The results were further optimized under engineering conditions to reduce costs and enable on-site quantification without relying on complex precision instruments. The quantitative results of pyrite in mineral samples were verified by the XRD internal standard method, and the error was less than 0.6%. This approach ensures the effective monitoring and management of sulfide content in concrete aggregates, promoting the practical application of sulfur-bearing aggregates. Full article
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19 pages, 5377 KiB  
Article
The Influence of Multi-Walled Carbon Nanotubes on the Pull-Off Strength of Polymer Concrete Overlays on Concrete Substrates with Sulfate Exposure
by Ali Akbarpour, Jeffery Volz and Shreya Vemuganti
J. Compos. Sci. 2025, 9(6), 272; https://doi.org/10.3390/jcs9060272 - 29 May 2025
Cited by 1 | Viewed by 448
Abstract
Polymer concrete (PC) is recognized for its lightweight nature, wear resistance, and rapid curing, making it well-suited for the repair of deteriorated infrastructure. This research critically addresses the challenge of enhancing overlay adhesion to compromised substrates by uniquely evaluating the role of pristine [...] Read more.
Polymer concrete (PC) is recognized for its lightweight nature, wear resistance, and rapid curing, making it well-suited for the repair of deteriorated infrastructure. This research critically addresses the challenge of enhancing overlay adhesion to compromised substrates by uniquely evaluating the role of pristine versus functionalized multi-walled carbon nanotubes (MWCNTs) in improving polymer concrete (PC) bond strength, particularly on concrete deteriorated by sulfate attack. PC mixtures containing varying concentrations of MWCNTs (0%, 0.25%, and 0.5% by weight) were prepared and tested for their mechanical properties, including compressive strength, modulus of rupture, and pull-off strength. Pull-off tests were conducted to assess the bond between PC overlays and Portland cement concrete (PCC) substrates. To examine the effects of substrate deterioration, PCC specimens were cured under two conditions: standard and sulfate-exposed environments. The results showed that neat polymer concrete (PC-Neat) achieved a high average pull-off strength of 2.82 MPa under normal conditions. Incorporating 0.25% pristine MWCNTs (PC-P25) significantly reduced the bond strength to 0.039 MPa. In contrast, improved performance was observed with functionalized MWCNTs. The addition of 0.5% COOH-functionalized MWCNTs (PC-FC50) yielded a pull-off strength of 2.22 MPa under normal conditions and 1.65 MPa in sulfate environments. Notably, under sulfate exposure, functionalized MWCNTs enhanced the bond strength by up to 15% compared to PC-Neat, highlighting their potential in aggressive environments. This distinct improvement in bond strength presents a significant finding, demonstrating a novel pathway for developing more resilient repair materials for infrastructure exposed to aggressive chemical environments. Full article
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22 pages, 7086 KiB  
Article
Corrosion Products and Microstructural Evolution of Ordinary Portland Cement and High-Performance Concrete After Eight Years of Field Exposure in Qarhan Salt Lake
by Zhiyuan Luo, Hongfa Yu, Haiyan Ma, Yongshan Tan, Chengyou Wu, Jingnan Sun, Xiaoming Wang and Peng Wu
Materials 2025, 18(8), 1769; https://doi.org/10.3390/ma18081769 - 12 Apr 2025
Cited by 2 | Viewed by 427
Abstract
Salt lakes and the surrounding saline soils distributed across northwestern China and Inner Mongolia impose severe physicochemical corrosion on cement-based concrete. Understanding the corrosion products and mechanisms are crucial scientific and technological factors in ensuring the durability and service life of concrete structures [...] Read more.
Salt lakes and the surrounding saline soils distributed across northwestern China and Inner Mongolia impose severe physicochemical corrosion on cement-based concrete. Understanding the corrosion products and mechanisms are crucial scientific and technological factors in ensuring the durability and service life of concrete structures in these regions. In this study, various analytical techniques—including X-ray diffraction, thermogravimetric–differential thermal analysis, X-ray fluorescence, and scanning electron microscopy coupled with energy-dispersive spectroscopy—were employed to systematically analyze the corrosion products of ordinary Portland cement (OPC) and high-performance concrete (HPC) specimens after eight years of field exposure in the Qarhan Salt Lake area of Qinghai. The study provided an in-depth understanding of the physicochemical corrosion mechanisms involved. The results showed that, after eight years of exposure, the corrosion products comprised both physical corrosion products (primarily sodium chloride crystals), and chemical corrosion products (associated with chloride, sulfate, and magnesium salt attacks). A strong correlation could be observed between the chemical corrosion products and the strength grade of the concrete. In C25 OPC, the detected corrosion products included gypsum, monosulfate-type calcium sulfoaluminate (AFm), Friedel’s salt, chloro-ettringite, brucite, magnesium oxychloride hydrate 318, calcium carbonate, potassium chloride, and sodium chloride. In C60 HPC, the identified corrosion products included Kuzel’s salt, Friedel’s salt, chloro-ettringite, brucite, calcium carbonate, potassium chloride, and sodium chloride. Among them, sulfate-induced corrosion led to the formation of gypsum and AFm, whereas chloride-induced corrosion resulted in chloro-ettringite and Friedel’s salt. Magnesium salt corrosion contributed to the formation of brucite and magnesium oxychloride hydrate 318, with Kuzel’s salt emerging as a co-corrosion product of chloride and sulfate attacks. Furthermore, a conversion phenomenon was evident between the sulfate and chloride corrosion products, which was closely linked to the internal chloride ion concentration in the concrete. As the chloride ion concentration increased, the transformation sequence of sulfate corrosion products occurred in the following order: AFm → Kuzel’s salt → Friedel’s salt → chloro-ettringite. There was a gradual increase in chloride ion content within these corrosion products. This investigation into concrete durability in salt-lake ecosystems offers technological guidance for infrastructure development and material specification in hyper-saline environments. Full article
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28 pages, 7825 KiB  
Review
Mechanism and Performance Control Methods of Sulfate Attack on Concrete: A Review
by Chuanchuan Zhang, Julun Li, Miao Yu, Yue Lu and Shizhong Liu
Materials 2024, 17(19), 4836; https://doi.org/10.3390/ma17194836 - 30 Sep 2024
Cited by 14 | Viewed by 5440
Abstract
For concrete structures in marine or groundwater environments, sulfate attack is a major factor contributing to the degradation of concrete performance. This paper analyzes the existing literature on the chemical reactions and physical crystallization effects of sulfate attack on cement-based materials, summarizing the [...] Read more.
For concrete structures in marine or groundwater environments, sulfate attack is a major factor contributing to the degradation of concrete performance. This paper analyzes the existing literature on the chemical reactions and physical crystallization effects of sulfate attack on cement-based materials, summarizing the degradation mechanisms of corroded concrete. Experiments have been conducted to study the performance evolution of concrete under sulfate attack, considering both external environmental factors and internal factors of the cement-based materials. External environmental factors, such as the temperature, humidity, concentration, and type of sulfate solutions, wet-dry cycles, freeze-thaw cycles, chloride coupling effects, and stray currents significantly impact sulfate attack on concrete. Internal factors, including internal sources of corrosion, the chemical composition of the cement, water-cement ratio, and the content of C-S-H gel and Ca(OH)2, influence the density and sulfate resistance of the cement-based materials. Additionally, five typical methods for enhancing the sulfate resistance of concrete are summarized. Finally, the paper identifies current challenges in the study of corroded concrete and proposes directions for future research. Full article
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19 pages, 10599 KiB  
Article
Effect of the Addition of Manganese Dioxide Nanoparticles on the Mechanical Properties of Concrete against Carbonation and Sulfate Attack
by Ana Torre, Luisa Shuan, Noemi Quintana, Isabel Moromi, Jesus Basurto, Luis Mosquera and Noe Cortez
Buildings 2024, 14(10), 3094; https://doi.org/10.3390/buildings14103094 - 26 Sep 2024
Cited by 1 | Viewed by 1170
Abstract
This study evaluates the impact of the addition of nanoparticles of anodic manganese dioxide (NAMD) on the mechanical properties and resistance to chemical attack of concrete. The research focused on nine concrete mixtures with water/cement ratios of 0.40, 0.45, and 0.50 and NAMD [...] Read more.
This study evaluates the impact of the addition of nanoparticles of anodic manganese dioxide (NAMD) on the mechanical properties and resistance to chemical attack of concrete. The research focused on nine concrete mixtures with water/cement ratios of 0.40, 0.45, and 0.50 and NAMD contents of 0, 5, and 10%. The properties of NAMD were analyzed, and fresh concrete properties such as temperature, unit weight, and consistency were measured. The compressive strength was determined at different ages (7, 14, 28, 56, and 90 days). The tensile and flexural strength were evaluated at 28 days, and the longitudinal change generated by the SO4Mg attack was monitored until 90 days. In addition, an accelerated carbonation test was performed on concrete samples with 28 days of curing exposed to an atmosphere of 6% CO2 for one week. The addition of NAMD did not significantly affect the temperature or unit weight of the fresh concrete, but it did influence the consistency. An increase in compressive, tensile, and flexural strength was observed, especially at early ages and for low w/c ratios. The addition of NAMD reduced the expansion of concrete exposed to magnesium sulfate, with 5% being the most effective dose, and reduced the carbonation rate of concrete by up to 40% in mixes with w/c ratios of 0.40 and 0.50. It was shown that the addition of 5% as an effective dose of NAMD improves the mechanical and durability properties of concrete, especially in mixtures with a low water/cement ratio, contributing to the improvement of the quality and strength of concrete. Full article
(This article belongs to the Section Building Materials, and Repair & Renovation)
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23 pages, 4423 KiB  
Review
Construction Sector Transition towards Smart Applications of Graphene Oxide in Cement-Based Composites: A Scientometric Review and Bibliometric Analysis
by Abdul Hannan Qureshi, Naveed Ahmad, Muhammad Ashar Atif Rana, Bilal Manzoor and Tarek Zayed
Buildings 2024, 14(10), 3042; https://doi.org/10.3390/buildings14103042 - 24 Sep 2024
Cited by 3 | Viewed by 2039
Abstract
Cement-based composites (CBCs) are essential in the construction sector due to their cost-effectiveness, availability, and versatility, but they struggle with low tensile strength and poor heat resistance. Recent advancements have highlighted the potential of nanomaterials, particularly graphene oxide (GO), in enhancing the mechanical, [...] Read more.
Cement-based composites (CBCs) are essential in the construction sector due to their cost-effectiveness, availability, and versatility, but they struggle with low tensile strength and poor heat resistance. Recent advancements have highlighted the potential of nanomaterials, particularly graphene oxide (GO), in enhancing the mechanical, thermal, and electrical properties of CBCs. This study aims to provide a comprehensive review of the incorporation of GO into cementitious composites, examining its impact on microstructure, mechanical properties, rheology, and durability; thus, a bibliometric review and scientometric analysis were conducted to thoroughly evaluate the existing literature. A total of 263 studies were selected for thorough study. It can be concluded that GO content acts as a pore filler, decreasing porosity by 23% and average pore size by 22%, while boosting compressive strength by up to 15% at a 0.05% concentration. It also enhances workability, stability, and resistance to chloride ingress, sulfate attack, alkali–silica reaction, and carbonation. Incorporating GO reduces cement consumption and carbon footprint, leading to more durable structures and supporting sustainable construction by efficiently utilizing waste materials. The optimal GO concentration for these benefits ranges from 0.03% to 0.1% by weight of cement, as higher concentrations may cause agglomeration. GO-modified cementitious materials are well suited for high-performance and durable applications, particularly in environments with chemical and mechanical stresses. Full article
(This article belongs to the Section Construction Management, and Computers & Digitization)
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18 pages, 3200 KiB  
Article
Levofloxacin Degradation, Antimicrobial Activity Decrease, and Potential for Water Disinfection Using Peroxydisulfate Activation by Ag/TiO2 under Sunlight
by Sindy D. Jojoa-Sierra, Cesar Jaramillo-Paez, Efraím A. Serna-Galvis, Inés García-Rubio, María C. Hidalgo, José A. Navío, María P. Ormad, Ricardo A. Torres-Palma and Rosa Mosteo
Water 2024, 16(17), 2434; https://doi.org/10.3390/w16172434 - 28 Aug 2024
Cited by 2 | Viewed by 1461
Abstract
Water quality and usability are global concerns due to microbial and chemical pollution resulting from anthropogenic activities. Therefore, strategies for eliminating contaminants are required. In this context, the removal and decrease in antibiotic activity (AA) associated with levofloxacin (LEV), using TiO2 and [...] Read more.
Water quality and usability are global concerns due to microbial and chemical pollution resulting from anthropogenic activities. Therefore, strategies for eliminating contaminants are required. In this context, the removal and decrease in antibiotic activity (AA) associated with levofloxacin (LEV), using TiO2 and Ag/TiO2 catalysts, with and without sunlight and peroxydisulfate, was evaluated. Additionally, the disinfection capacity of catalytic systems was assessed. The catalysts were synthesized and characterized. Moreover, the effect of Ag doping on visible light absorption was determined. Then, the photocatalytic treatment of LEV in water was performed. The materials characterization and EPR analyses revealed that LEV degradation and AA decrease were ascribed to a combined action of solar light, sulfate radical, and photocatalytic activity of the TiO2-based materials. Also, the primary byproducts were elucidated using theoretical analyses (predictions about moieties on LEV more susceptible to being attacked by the degrading species) and experimental techniques (LC-MS), which evidenced transformations on the piperazyl ring, carboxylic acid, and cyclic ether on LEV. Moreover, the AA decrease was linked to the antibiotic transformations. In addition, the combined system (i.e., light/catalyst/peroxydisulfate) was shown to be effective for E. coli inactivation, indicating the versatility of this system for decontamination and disinfection. Full article
(This article belongs to the Special Issue Control and Treatment of Emerging Contaminants in Water Ecosystems)
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14 pages, 861 KiB  
Review
Modeling of Concrete Deterioration under External Sulfate Attack and Drying–Wetting Cycles: A Review
by Shanshan Qin, Chuyu Chen and Ming Zhang
Materials 2024, 17(13), 3334; https://doi.org/10.3390/ma17133334 - 5 Jul 2024
Cited by 5 | Viewed by 1816
Abstract
This paper comprehensively summarizes moisture transport, ion transport, and mechanical damage models applied to concrete under sulfate attack and drying–wetting cycles. It highlights the essential aspects and principles of each model, emphasizing their significance in understanding the movement of moisture and ions, as [...] Read more.
This paper comprehensively summarizes moisture transport, ion transport, and mechanical damage models applied to concrete under sulfate attack and drying–wetting cycles. It highlights the essential aspects and principles of each model, emphasizing their significance in understanding the movement of moisture and ions, as well as the resulting mechanical damage within the concrete during these degradation processes. The paper critically analyzes the assumptions made in each model, shedding light on their limitations and implications for prediction accuracy. Two primary challenges faced by current models under sulfate attack and drying–wetting cycles are identified: the limited consideration of the coupled effects of chemical and physical attacks from sulfate, and the unclear mechanism of the sulfate attacks. Future research directions are proposed, focusing on exploring the transport mechanism of sulfate ions under various driving forces and further clarifying the crystallization process and expansion damage mechanism in concrete pores. Addressing these research directions will advance our understanding of sulfate attack under drying–wetting cycles, leading to improved models and mitigation strategies for enhancing the durability and performance of concrete structures. Full article
(This article belongs to the Special Issue New Advances in Cement and Concrete Research2nd Edition)
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13 pages, 5610 KiB  
Article
Table Olive Manufacturing Wastewater Treatment Using the Peroxymonosulfate/Fe(III) System
by Francisco Javier Rivas, Fernando J. Beltrán and Olga Gimeno
Catalysts 2024, 14(2), 121; https://doi.org/10.3390/catal14020121 - 2 Feb 2024
Cited by 1 | Viewed by 1702
Abstract
Wastewater generated in table olive manufacturing processes (WWTOMP) is a seasonal waste difficult to manage due to the high salinity content. The treatment of WWTOMP has been accomplished by including a precoagulation stage with aluminum sulfate, oxidation using the peroxymonosulfate/Fe(III) system, and a [...] Read more.
Wastewater generated in table olive manufacturing processes (WWTOMP) is a seasonal waste difficult to manage due to the high salinity content. The treatment of WWTOMP has been accomplished by including a precoagulation stage with aluminum sulfate, oxidation using the peroxymonosulfate/Fe(III) system, and a final aerobic biological stage. The optimum conditions of precoagulation led to a chemical oxygen demand removal rate of roughly 30–35% without the need for pH adjustment. The peroxymonosulfate(PMS)/Fe(III) system was thereafter applied to the effluent after coagulation. The addition of PMS lowered the initial pH to acidic conditions (pH = 1.5–2.0). Under these operating conditions, the initial PMS concentration and the initial Fe(III) dose showed optimum values. An excess of the oxidant and/or the catalyst partially inhibited the process efficiency, and pH exerted a significant influence. COD removal was substantially increased as the pH of the solution was moved toward circumneutral values in the interval 5–4. Moreover, at pH values of 5 and 7, PMS was capable of reducing COD without the need for Fe(III) presence. The direct oxidation of organics by PMS or the generation of chloride-based oxidants (Cl2 or HClO) is suggested to occur in parallel to the radical attack from PMS decomposition. An attempt to biologically reduce the final COD to discharge limits failed, mainly due to the high salinity content; however, the 1:2 dilution led to the reduction in COD from 6 to 2 g L−1. Acclimated sludges or saline content reduction should be first considered. Full article
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19 pages, 4802 KiB  
Article
Chemical Mechanisms Involved in the Coupled Attack of Sulfate and Chloride Ions on Low-Carbon Cementitious Materials: An In-Depth Study
by François El Inaty, Mario Marchetti, Marc Quiertant and Othman Omikrine Metalssi
Appl. Sci. 2023, 13(21), 11729; https://doi.org/10.3390/app132111729 - 26 Oct 2023
Cited by 10 | Viewed by 3217
Abstract
This study aims to analyze the individual and combined chemical attacks of sulfate and chloride ions on cementitious materials and assess the efficiency of some selected additives (fly ash, blast furnace slag, and metakaolin) in countering this combined attack. This research is conducted [...] Read more.
This study aims to analyze the individual and combined chemical attacks of sulfate and chloride ions on cementitious materials and assess the efficiency of some selected additives (fly ash, blast furnace slag, and metakaolin) in countering this combined attack. This research is conducted in the context of construction in marine environments, where reinforced concrete structures are often subject to significant challenges due to early exposure to sulfate and chloride ions. This early exposure results in concrete expansion, cracking, and, ultimately, the corrosion of steel reinforcements. Nevertheless, the interaction between sulfate ions, chloride ions, and the cementitious matrix remains poorly understood. Previous research has drawn conflicting conclusions, with some suggesting that sulfate ions mitigate chloride attacks, while others have come to the opposite conclusion. During this study, experimental investigations were conducted by immersing powders obtained from crushed ordinary Portland cement (CEM I) paste specimens, as well as binary, ternary, and quaternary blends, in sulfate, chloride, and sulfate–chloride solutions over the course of 25 days at an early age. Results from different characterization techniques (thermogravimetric analysis, Fourier Transform Infrared spectroscopy, Raman spectroscopy, etc.) indicate that chloride ions delay the formation of ettringite, while the presence of sulfate ions accelerates the chloride attack by limiting the formation of Friedel’s salt. The Mercury Intrusion Porosimetry test confirmed these results by showing a pronounced increase in specimens’ porosity after exposure to solely sulfate after 25 days, compared to the ones exposed to both sulfate and chloride ions. Furthermore, the incorporation of multiple additives, particularly in ternary and quaternary blends, demonstrates the enhanced durability of the studied samples. This was confirmed by a Fourier Transform Infrared spectroscopy analysis, which indicated a delayed ettringite formation in these mixtures. This delay was further affirmed by the complete depletion of sulfate ions in the sulfate solutions upon contact with powders derived from the 100% CEM I paste. Full article
(This article belongs to the Section Materials Science and Engineering)
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16 pages, 6791 KiB  
Article
Strength Degradation of Foamed Lightweight Soil Due to Chemical Erosion and Wet-Dry Cycle and Its Empirical Model
by Zhen Zhang, Yonggang Zhang, Guanbao Ye, Shenyi Zhang, Honghui Shen and Yonggui Chen
Materials 2023, 16(19), 6505; https://doi.org/10.3390/ma16196505 - 30 Sep 2023
Cited by 8 | Viewed by 1290
Abstract
Foamed lightweight soils (FLS) have been extensively used as backfill material in the construction of transportation infrastructures. However, in the regions consisting of salt-rich soft soil, the earth structure made by FLS experiences both fluctuation of groundwater and chemical environment erosion, which would [...] Read more.
Foamed lightweight soils (FLS) have been extensively used as backfill material in the construction of transportation infrastructures. However, in the regions consisting of salt-rich soft soil, the earth structure made by FLS experiences both fluctuation of groundwater and chemical environment erosion, which would accelerate the deterioration of its long-term performance. This study conducted laboratory tests to explore the deterioration of FLS in strength after being eroded by sulfate attack and/or wet-dry cycling, where the influencing factors of FLS density, concentration of sulfate solution, and cation type (i.e., Na+ and Mg2+) were considered. An unconfined compressive test (UCT) was conducted, and the corrosion-resistant coefficient (CRC) was adopted to evaluate the erosion degree after the specimens experienced sulfate attack and/or dry-wet cycling for a certain period. The research results show that the erosion of the FLS specimen under the coupling effect of sulfate attack and dry-wet cycling was more remarkable than that only under chemical soaking, and Na2SO4 solution had a severe erosion effect as compared with MgSO4 solution when other conditions were kept constant. An empirical model is proposed based on the test results, and its reliability has been verified with other test results from the literature. The proposed model provides an alternative for engineers to estimate the strength deterioration of FLS on real structures in a preliminary design. Full article
(This article belongs to the Special Issue Advanced Geomaterials and Reinforced Structures)
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19 pages, 3710 KiB  
Article
Absorption and Utilization of Pollutants in Water: A Novel Model for Predicting the Carrying Capacity and Sustainability of Buildings
by Enyang Mei and Kunyang Yu
Water 2023, 15(17), 3152; https://doi.org/10.3390/w15173152 - 3 Sep 2023
Viewed by 1759
Abstract
The combination of water management and urban planning can promote the sustainable development of cities, which can be achieved through buildings’ absorption and utilization of pollutants in water. Sulfate ions are one of the important pollutants in water, and concrete is an important [...] Read more.
The combination of water management and urban planning can promote the sustainable development of cities, which can be achieved through buildings’ absorption and utilization of pollutants in water. Sulfate ions are one of the important pollutants in water, and concrete is an important building material. The absorption of sulfate ions by concrete can change buildings’ bearing capacity and sustainability. Nevertheless, given the complex and heterogeneous nature of concrete and a series of chemical and physical reactions, there is currently no efficient and accurate method for predicting mechanical performance. This work presents a deep learning model for establishing the relationship between a water environment and concrete performance. The model is constructed using an experimental database consisting of 1328 records gathered from the literature. The utmost essential parameters influencing the compressive strength of concrete under a sulfate attack such as the water-to-binder ratio, the sulfate concentration and type, the admixture type and percentage, and the service age are contemplated as input factors in the modeling process. The results of using several loss functions all approach 0, and the error between the actual value and the predicted value is small. Moreover, the results also demonstrate that the method performed better for predicting the performance of concrete under water pollutant attacks compared to seven basic machine learning algorithms. The method can serve as a reference for the integration of urban building planning and water management. Full article
(This article belongs to the Special Issue Water-Sensitive and Sustainable Urban Development)
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16 pages, 5044 KiB  
Article
Effect of an Early-Age Exposure on the Degradation Mechanisms of Cement Paste under External Sulfate Attack
by Othman Omikrine Metalssi, Rim Ragoug, Fabien Barberon, Jean-Baptiste d’Espinose de Lacaillerie, Nicolas Roussel, Loïc Divet and Jean-Michel Torrenti
Materials 2023, 16(17), 6013; https://doi.org/10.3390/ma16176013 - 1 Sep 2023
Cited by 10 | Viewed by 1978
Abstract
Among the most significant causes of concrete degradation is ESA (external sulfate attack). The majority of studies are currently conducted on samples that have been saturated and matured. Concrete structures, however, are exposed to the environment once the formwork has been removed. The [...] Read more.
Among the most significant causes of concrete degradation is ESA (external sulfate attack). The majority of studies are currently conducted on samples that have been saturated and matured. Concrete structures, however, are exposed to the environment once the formwork has been removed. The purpose of this study is to determine what effects early exposure to external sulfates may have on degradation mechanisms. Microstructure, physical, and chemical behavior are monitored using a variety of experimental techniques, including NMR (27Al and 29Si), ICP, XRD, MIP, and SEM. Based on expansion measurements, mature Portland cement paste, unlike the early-age case, degraded rapidly due to the presence of compressed ettringite and gypsum, highlighted by SEM analysis. During ESA, sulfate ions diffuse through the cement matrix and are bound by chemical agents. Chemical analyses indicate that the chemical mechanism varies with the duration of curing. At an early age, external sulfates and aluminates are the most important reagents. For matured cases, these reagents include external sulfates, calcium derived from CH dissolution, and aluminates derived from the total dissolution of AFm. Full article
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16 pages, 5872 KiB  
Article
A Micromechanical-Based Semi-Empirical Model for Predicting the Compressive Strength Degradation of Concrete under External Sulfate Attack
by Shagang Li, Xiaotong Yu, Shanyin Yang, Hongxiang Wang and Da Chen
Materials 2023, 16(16), 5542; https://doi.org/10.3390/ma16165542 - 9 Aug 2023
Cited by 2 | Viewed by 1605
Abstract
As one of the most harmful ions in the environment, sulfate could cause the deformation and material deterioration of concrete structures. Models that accurately describe the whole chemo–transport–mechanical process of an external sulfate attack (ESA) require substantial computational work and contain complex parameters. [...] Read more.
As one of the most harmful ions in the environment, sulfate could cause the deformation and material deterioration of concrete structures. Models that accurately describe the whole chemo–transport–mechanical process of an external sulfate attack (ESA) require substantial computational work and contain complex parameters. This paper proposes a semi-empirical model based on micromechanical theory for predicting the compressive strength degradation of concrete under an ESA with basic properties of the undamaged material and limited computational effort. A simplified exponential function is developed for the total amount of the invading sulfate, and a second-order equation governs the chemical reaction. A micromechanical model is implemented to solve the mechanical response caused by an ESA. The model is able to describe the compressive stress–strain behavior of concrete subject to uniaxial loading in good agreement with the experimental results. For the case of a sulfate-attacked material, the relationship between compressive strength and expansion is calculated and validated by the test results. Finally, the deterioration process of compressive strength is predicted with the test results of deformation. Full article
(This article belongs to the Special Issue Mechanical Behaviors of Materials: Modelling and Measurement)
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