The construction industry urgently requires sustainable alternatives to conventional cement to mitigate its environmental footprint, which includes 8% of global CO₂ emissions. This review critically examines the potential of rice husk ash (RHA) and silica fume (SF)—industrial and agricultural byproducts—as high-performance supplementary cementitious materials (SCMs) in soil–cement composites. Their pozzolanic reactivity, microstructural enhancement mechanisms, and durability improvements (e.g., compressive strength gains of up to 31.7% for RHA and 250% for SF) are analyzed. This study highlights the synergistic effects of RHA/SF blends in refining pore structure, reducing permeability, and enhancing resistance to chemical attacks. Additionally, this paper quantifies the environmental benefits, including CO₂ emission reduction (up to 25% per ton of cement replaced) and resource recovery from agricultural/industrial waste streams. Challenges such as material variability, optimal dosage (10–15% RHA, 5–8% SF), and regulatory barriers are discussed, alongside future directions for scalable adoption. This work aligns with SDGs 9, 11, and 12, offering actionable insights for sustainable material design.

The synergistic interaction between freeze–thaw cycles and sulfate attack induces a more severe and complex deterioration mechanism in concrete than either factor in isolation. This review elucidates this process by first examining the individual damage mechanisms and then integrating current research to analyze the coupled effects, revealing a complex process involving the superposition and competition of physical crystallization, chemical reactions, and fatigue stresses. The deterioration is delineated into four distinct stages: (1) Pre-Inflection Acceleration, (2) Post-Inflection Acceleration, (3) Deceleration, and (4) Rapid Failure. Experimental methodologies, research materials, and study protocols are critically examined, with particular emphasis on the influence of sulfate solution type and concentration, while highlighting significant discrepancies between laboratory conditions and field exposure. Based on this, the existing durability damage models and multi-physics numerical simulation methods are summarized, emphasizing the importance of cross-scale studies. Finally, prioritized research directions are proposed, emphasizing the need for refined experimental protocols and integrated physico-chemical models to advance predictive durability assessment. This work provides a foundational reference for guiding future research in concrete durability.

To investigate the influence of the water–cement ratio and erosion patterns on the deterioration of concrete in a sulfate corrosion environment, concrete specimens with different water–cement ratios were immersed in Na₂SO₄ solutions of varying concentrations (0%, 5%, and 8%). The immersion times were set at 0 days, 30 days, 60 days, and 90 days. Macro-scale compressive strength tests and micro-scale performance tests were conducted to obtain the damage morphology, micro-scale elastic modulus, and hardness of eroded concrete. Additionally, K-means clustering analysis was used to analyze the micro-mineral phases of the specimens, and SEM and XRD were employed to reveal the degradation mechanisms of sulfate erosion on the microstructure of concrete. The results indicated that the erosion products of calcium aluminate and gypsum in concrete gradually increased with the increase in Na₂SO₄ solution concentration and immersion time. In the early stages of erosion, the compressive strength and corrosion resistance coefficient of concrete showed a temporary upward trend, which then decreased as the erosion depth increased. From a microstructural perspective, erosion had a significant impact on the internal structure of concrete, while the elastic modulus and hardness of hydrated calcium silicate and calcium hydroxide under erosion showed relatively minor changes, both exhibiting a gradual decrease. The volume fraction of microporous pores gradually increased, further exacerbating the depth and extent of erosion.

To investigate the micro-mechanism of the erosion of hydrated calcium silicate (C-S-H gel) in a sulfate environment, a solid–liquid molecular dynamics model of C-S-H gel/sodium sulfate was developed. This model employs molecular dynamics methods to simulate the transport processes between C-S-H gel and corrosive ions at concentrations of 5%, 8%, and 10% sodium sulfate (Na₂SO₄), aiming to elucidate the interaction mechanism between sulfate and C-S-H gel. The micro-morphology of the eroded samples was also investigated using scanning electron microscopy (SEM). The findings indicate that the adsorption capacity of C-S-H for ions significantly increases with higher concentrations of Na₂SO₄ solution. Notably, the presence of sulfate ions facilitates the decalcification reaction of C-S-H, leading to the formation of swollen gypsum and AFt (ettringite). This process results not only in the hydrolysis of the C-S-H gel but also in an increase in the diffusion coefficients of Na⁺ and Ca²⁺, thereby exacerbating the erosion. Additionally, the pore surfaces of the C-S-H structure exhibited strong adsorption of Na⁺, and as the concentration of Na₂SO₄ solution increased, Na+ was more stably adsorbed onto the C-S-H pore surfaces via Na-O_s bonds. The root-mean-square displacement curves of water molecules were significantly higher than those of ${\mathrm{SO}}_4^{2-}$, Na⁺ and Ca²⁺, which indicated that ${\mathrm{SO}}_4^{2-}$ could co-penetrate and migrate with water molecules faster compared with other ions in the solution containing ${\mathrm{SO}}_4^{2-}$, resulting in stronger corrosion and hydrolysis effects on the C-S-H structure.

Incorporating intelligent materials in concrete allows for self-sensing capabilities by reflecting the concrete’s strain and tensile status through the electrical properties. In order to enhance the self-diagnostic abilities of intelligent concrete, we conducted research on how intelligent materials affect the fracture mechanics of concrete. This study examines the fracture mechanical properties of the carbon nanofiber cement mortar and paste based on three-point bending and nanoindentation tests. The results showed that the carbon nanofiber content has negligible influence on the crack initiation toughness of the specimens. However, the instability toughness exhibited an initial increase followed by a decrease as the carbon nanofiber content increased. At a fiber content of 0.2%, the crack initiation toughness improved maximally by 13.1% compared to the control group. At a fiber content of 0.5%, both the ductility index and fracture energy increased with the nanofiber content, improving by 84% and 66.3%, respectively. The incorporation of carbon nanofibers did not alter the composition of cement paste hydration products; the fracture toughness of each hydration product varies from 0.14 to 0.59 MPa·m^1/2. However, the fracture toughness of individual hydration products and un-hydrated particles is higher than the macroscopic three-point bending fracture toughness values of the specimens.

This study investigates the synergistic modification of cement–soil using waste brick powder (WBP) and polyvinyl alcohol (PVA) fibers to address the growing demand for sustainable construction materials and recycling of demolition waste. An orthogonal experimental design was employed with 5% WBP (by mass) and PVA fiber content (0–1%), evaluating mechanical properties based on unconfined compressive strength (UCS) and splitting tensile strength (STS) and microstructure via scanning electron microscopy (SEM) across 3–28 days of curing. The results demonstrate that 0.75% PVA optimizes performance, enhancing UCS by 28.3% (6.87 MPa) and STS by 34.6% (0.93 MPa) at 28 days compared to unmodified cement–soil. SEM analysis revealed that PVA fibers bridged microcracks, suppressing propagation, while WBP triggered pozzolanic reactions to densify the matrix. This dual mechanism concurrently improves mechanical durability and valorizes construction waste, offering a pathway to reduce reliance on virgin materials. This study establishes empirically validated mix ratios for eco-efficient cement–soil composites, advancing scalable solutions for low-carbon geotechnical applications. By aligning material innovation with circular economy principles, this work directly supports global de-carbonization targets in the construction sector.