Conventional materials necessitate a layer-by-layer rolling or tamping process for subgrade backfill projects, which hampers their utility in confined spaces and environments where compaction is challenging. To address this issue, a self-compacting poured solidified mucky soil was prepared. To assess the suitability of this innovative material for subgrade, a suite of performance including flowability, bleeding rate, setting time, unconfined compressive strength (UCS), and deformation modulus were employed as evaluation criteria. The workability and mechanical properties of poured solidified mucky soil were compared. The durability and solidification mechanism were investigated. The results demonstrate that the 28-day UCS of poured solidified mucky soil with 20% curing agent content reaches 2.54 MPa. The increase of organic matter content is not conducive to the solidification process. When the curing temperature is 20 degrees C, the 28-day UCS of the poured solidified mucky soil with curing agent content not less than 12% is greater than 0.8 MPa. The three-dimensional network structure formed with calcium silicate hydrate, calcium aluminate hydrate, and ettringite is the main source of strength formation. The recommended mud moisture content is not exceed 85%, the curing agent content is 16%, and the curing temperature should not be lower than 20 degrees C.

Waste red layers have the potential to be used as supplementary cementitious materials after calcination, but frequent and long-term dry-wet cycling leads to deterioration of their properties, limiting their large-scale application. In this study, the feasibility of using calcined red layers as cement replacement materials under dry-wet cycling conditions was analyzed. The damage evolution and performance degradation of calcined red layer-cement composites (RCC) were systematically evaluated via the digital image correlation (DIC) technique, scanning electron microscopy (SEM) analysis and damage evolution mode. The results show that the calcined red layer replacement ratio and number of dry-wet cycles affect the hydration and pozzolanic reactions of the materials and subsequently affect their mechanical properties. Based on the experimental data, a multiple regression model was developed to quantify the combined effects of the number of dry-wet cycles and the replacement ratio of the calcined red layer on the uniaxial compressive strength. As the number of dry-wet cycles increases, microcracks propagate, the porosity increases, and damage accumulation intensifies. In particular, at a high substitution ratio, the material properties deteriorate further. The global strain evolution process of a material can be accurately tracked via DIC technology. The damage degree index is defined based on strain distribution law, and a damage evolution model was constructed. At lower dry-wet cycles, the hydration reaction has a compensatory effect on damage. The pozzolanic reaction of the calcined red layer resulted in an increase in the number of dry-wet cycles. The RCC samples with high replacement ratios show significant damage accumulation with fast damage growth rates at lower stress levels. The model reveals the nonlinear effects of dry-wet cycling and the calcined red layer replacement ratio on damage accumulation in RCC. The study findings establish a scientific foundation for the resource utilization of abandoned red layers and serve as a significant reference for the durability design of materials in practical engineering applications.

The lack of global standardization in the testing methods for Stabilized Rammed Earth (SRE) hinders progress in advancing knowledge of this sustainable construction technique. This review compiles research from the last four years on SRE, focusing on manufacturing parameters, curing conditions, chemical stabilizer kinds, stabilizer dosage, testing methods, and mechanical and durability properties. Based on this analysis, a methodology is proposed to define and standardize SRE manufacturing parameters, curing, and testing conditions. The proposed methodology suggests that soil particle size distribution should be optimized to enhance mechanical strength and durability while reducing stabilizer dosage. The selection and dosage of stabilizers should be determined based on soil characteristics and environmental considerations. The standard proctor test is recommended for assessing manufacturing conditions, while curing should be performed by wrapping samples in plastic at laboratory temperature. Unconfined Compressive Strength is identified as the most relevant mechanical test and should be conducted at 7, 28, and 90 days. For durability assessment, erosion testing and exposure to liquid water are recommended at 28 days. This methodology represents one of the first steps toward the standardization of SRE testing methods, which must be accepted and adopted by researchers and practitioners. By implementing this methodology, comparable results across studies could be achieved, facilitating further research and collaboration among researchers. Such efforts would contribute to enhancing the available knowledge to improve the material's performance and further promote SRE as a sustainable construction technique.

Currently, the application of enhancement techniques with natural additives for soil stabilization is crucial due to growing urbanization and environmental concerns. Contemporary construction methods increasingly need eco-friendly and cost-effective materials, such as natural fibers. Reinforcing the soil sublayers with fibers improves layer quality and increases its load transfer capacity over a larger surface, thereby reducing the required thickness of upper layers. This study utilized raspberry stalks and xanthan biopolymer as natural additives for the first time to improve the mechanical qualities of bentonite expansive soil. Different tests, including compression and indirect tensile strengths, swelling potential, freeze-thaw (F-T) cycles, California bearing ratio (CBR), and scanning electron microscopy (SEM), were performed on samples comprising 0.2, 0.4, and 0.6 % of raspberry fibers and 0.5, 1, and 2 % of xanthan gum, with curing durations of 1, 7, 14, and 28 days. The test results revealed that the combination of 1 % xanthan and 0.4 % fibers, subjected to 28 days of curing, showed the best performance in increasing the mechanical properties of bentonite. The hydrogel structure and the locks and links formed in the soil by the additives led to increases of 353 % and 103 % in compressive and tensile strengths, respectively. The results also indicated that the free-swelling potential of the unstabilized bentonite soil diminished from 280 % to 74 % when stabilized with optimum percentages of xanthan and fiber. Furthermore, the investigation showed that even after exposure to 10 F-T cycles, the durability of xanthan-fiber-stabilized bentonite soil was significantly higher compared to the unstabilized soil. Moreover, the CBR value of the stabilized soil improved by 143 % compared to the unstabilized soil, indicating a significant increase in soil layer quality. The SEM results verified that the additive combination significantly impacted the strength of the samples. The data indicate that the incorporation of xanthan gum as a bio cohesive agent and raspberry fiber as tensile strands enhances soil strength, hence augmenting the viability of these additives in practical applications, including shallow foundations, adobe brick, and subgrade.

Freeze-thaw cycles coupled with sulfate attack represent one of the most challenging service environments for concrete. This study aims to enhance the durability of concrete materials in environments characterized by sulfate attack and severe freeze-thaw conditions. Specifically, it investigates the deterioration laws and evolution models of mortar materials containing silica fume under both freeze-thaw and coupled freeze-thaw/sulfate attack conditions. Mortar specimens with varying silica fume contents (0%, 6%, 8%, and 10%) were prepared and subjected to single freeze-thaw and coupled freeze-thaw-sulfate attack tests to examine the impact of different silica fume dosages on the durability of mortar materials under these harsh conditions. Additionally, a quantitative assessment model for damage evolution was established using the entropy weight method and Wiener process model. The research findings indicate that silica fume significantly enhances the sulfate resistance and freeze-thaw durability of mortar materials, with an optimal dosage of 10%. Within the scope of this study, higher silica fume content results in a greater number of sulfate attack-freeze-thaw cycles the mortar can endure before damage and failure, thereby extending its service life. Based on the Wiener stochastic process damage model and field data, it is predicted that the service life of mortar containing 10% silica fume increases most notably to 36.6 years, representing a relative improvement of 45.8 % compared to mortar without silica fume. These results provide valuable references and guidance for the design and construction of concrete structures in regions characterized by high-cold temperatures and salt- corrosive soils.

Ultra-high performance concrete (UHPC), due to its superior mechanical and durability properties, is extensively applied in saline soil areas. In this paper, the damage evolution process and constitutive relationship of UHPC under sulfate dry-wet cycling were investigated through mechanical property tests combined with acoustic emission (AE) technology. The results showed that With the increase in erosion cycles and SO42- content, the proportion of low-amplitude (<= 50 dB) AE events exhibited a decreasing trend. In contrast, the fraction of medium-and high-amplitude AE events gradually increased, suggesting that large-scale damage began to play a dominant role in the specimen's deterioration process. Based on AE characteristic parameters, the damage evolution model of UHPC under uniaxial compression was established, the model can effectively characterize the uniaxial compression damage evolution behavior of UHPC under sulfate dry-wet cycling, providing theoretical support for the service performance evaluation of UHPC structures in saline soil areas.

Improving soil properties by adding stabilizing materials, such as cement, has garnered significant attention from researchers, particularly for enhancing soils often deemed poor geotechnical quality. This approach becomes even more advantageous when applied to increase the stability of mining tailings deposits and ensure environmental safety. This study investigates the effects of cement addition and dry density on the strength and durability of compacted bauxite tailings-cement blends. The porosity/cement index, widely used in soil-cement mixture research, was adopted to analyze the parameters that control the strength and durability of these blends. Results demonstrate that increasing cement content and dry density significantly improves unconfined compressive strength (qu) and reduces accumulated mass loss (ALM) during wet/dry cycles. The porosity/cement index effectively describes the variations in qu and ALM, as expressed by an empirical equation, which can be highly beneficial for the practical application of treated mining tailings as construction materials.

This research explores the innovative resilience and self-healing properties of engineered cementitious composites (ECC) reinforced with shape memory alloy (SMA) fibers, tailored for environments susceptible to saltinduced freeze-thaw damage from deicing salts, seawater, and saline soils. The study examines ECC composites enhanced with varying SMA fiber volumes 0 %, 0.5 %, 0.75 %, and 1 % and three fiber shapes linear, indented, and hook-shaped, with an additional sandblasting surface treatment. Systematic analyses of monotonic and cyclic flexural behavior, as well as self-healing efficacy, were performed across four distinct freeze-thaw cycles (0, 50, 100, and 150) within environments of fresh water and a 3.5 % NaCl solution. Digital Image Correlation (DIC) was employed to precisely monitor the self-healing performance. The results highlight substantial enhancements in SMA-ECC, particularly improved flexural strength by up to 35 %, 30 %, and 17 % for hook, indented, and linear fibers respectively in freshwater. These gains were slightly reduced under saltwater conditions to 32 %, 26 %, and 15 % respectively. Additionally, crack-closure efficiencies in significant self-healing with improvements of 45 %, 38 %, and 27 % for hook, indented, and linear fibers respectively. The Weibull probability distribution model was used to establish the damage evolution equation of the SMA-ECC in two freeze-thaw environments. The results of this study can serve as a reference for the development of freeze-thawresistant designs for SMA-ECC structures in future applications.

Foamed lightweight soil (FLS) is frequently used for roadbed backfilling; however, excessive cement use contributes to higher costs and energy consumption. Desulfurized gypsum (DG), a by-product of industrial processing with a chemical composition similar to natural gypsum, presents a viable alternative to cement. This study evaluates the potential of DG to replace cement in FLS, creating a new material, desulfurized gypsum foamed lightweight soil (DG-FLS). This article is conducted on DG-FLS with varying DG content (0-30%) to assess its flowability, water absorption, unconfined compressive strength (UCS), durability, and morphological characteristics, with a focus on its suitability for roadbed backfilling, though its performance over the long term in engineering applications was not evaluated. Results show that as DG content increased, flowability, water absorption, and UCS decreased, with values falling within the range of 175-183 mm, 8.24-12.49%, and 0.75-2.75 MPa, respectively, all of which meet embankment requirements. The inclusion of DG enhanced the material's plasticity, improving failure modes and broadening its applicability. Durability tests under wet-dry and freeze-thaw cycles showed comparable performance to traditional FLS, with UCS exceeding 0.3 MPa. Additionally, the incorporation of SO42- in DG-FLS reduced sulfate diffusion, decreased C-S-H content, and increased calcium sulfate content, improving sulfate resistance. After 120 days of exposure to sulfates, the durability coefficient of DG-FLS surpassed 100%, with a 25% improvement over traditional FLS. A sustainability analysis revealed that DG-FLS not only meets engineering strength requirements but also offers economic and environmental benefits. Notably, DG-12 showed a 20% reduction in environmental impact compared to conventional FLS, underscoring its potential for more sustainable construction.

In this study, the role of zeolite and polyvinyl alcohol (PVA) fibers on the durability of cement-stabilized clayey sand soil under freeze-thaw and wet-dry cycles was investigated. Laboratory tests, including unconfined compressive strength (UCS), scanning electron microscope (SEM), and ultrasonic pulse velocity (UPV), were performed to evaluate the effect of zeolite replacement ratio and fiber content on the durability and mechanical characteristics of the stabilized soil. The results showed that the mechanical properties of cemented samples decreased significantly under wet-dry cycles compared to freeze-thaw cycles. The optimal zeolite replacement ratio to achieve the most appropriate durability behavior of cement-treated clayey sand was 20%. Compared to the unreinforced samples, the samples with 0.8% fibers showed a lower reduction in UCS and mass loss under wet-dry and freeze-thaw cycles. The reduction in UCS was limited to 13% and 15%, respectively. The mass loss was limited to 5.2%, which indicates the positive effect of fibers in improving the durability of soil. Samples containing zeolite and fibers had lower mass loss in wet-dry and freeze-thaw conditions than samples without zeolite and fibers. Finally, the SEM microstructural observations justified the results of the durability tests.