This study aims to investigate the chloride diffusion behavior of alkali activated slag and fly ash blends with different contents of waste glass powder (GP) addition. The reaction heat flow of alkali activated slag/fly ash/waste glass is characterized. The reaction products are determined by X-ray diffraction and thermogravimetric analysis (TGA). N2 adsorption analysis (BET) is used to evaluate the microstructure of samples. The accelerated chloride penetration test (ACPT) is applied to study the chloride resistance of the AAMs. Subsequently, the leaching test of chloride penetrated samples are conducted and ion chromatography is utilized to measure the chloride content in the samples. According to the BET results, the total volume of mesopores decreases with increasing GP content. The results of ACPT show that the increasing GP in AAMs shows an enhancement of chloride resistance.

The application of polymer latex provides an additional approach when optimizing the properties of high–performance cement–based materials. Given that cement–based materials are extraordinarily sensitive to the characteristics and relative content of polymer latexes, identifying their influence is essential for application. This paper investigates the impact of polymer latex types and its relative content on the mechanical properties, hydration product, pore structure, and drying shrinkage of cement–based materials with a low water to binder ratio. The results showed that the mechanical properties, pore structure, and drying shrinkage of the styrene butadiene latex modified samples were better than those of ethylene vinyl acetate latex and silicone acrylic latex modified ones. Incremental increases to the polymer to cement ratio induces a slight reduction on compressive strength, and styrene–butadiene latex promotes tensile strength. Polymer latex hinders the transformation from ettringite to monosulfate, reducing the bound water and portlandite generated. Increasing the polymer content induces more significant stretching in the vibration peak of SO₄ from ettringite. Further incorporation of polymer latex contributes to ettringite precipitation and the decline of harmful pores. Polymer addition also results in lower drying shrinkage compared with the reference group.

To simultaneously address the deterioration of mechanical properties in lightweight aggregate concrete (LAC) and the insufficient deformation control capacity of hybrid fiber-reinforced polymer (BFRP) bars, an experimental study on the flexural behavior of hybrid fiber-reinforced BFRP-LAC beams was conducted. A total of eight beams with dimensions of 120 mm × 200 mm × 2000 mm were fabricated. The effects of hybrid fibers and BFRP reinforcement ratio on the flexural performance were investigated. Four-point bending tests were performed to analyze the failure modes, load–deformation responses, crack development patterns, and sectional strain distributions. The results indicate that two failure modes were experimentally observed in the BFRP-reinforced hybrid fiber LAC beams, namely concrete crushing and BFRP bar rupture, whereas balanced failure was considered a theoretical failure condition. The failure mode was strongly dependent on the reinforcement ratio. At a low reinforcement ratio ($\rho$ = 0.68%), tensile failure governed by BFRP bar rupture occurred. At a moderate reinforcement ratio ($\rho$ = 1.02%), a relatively ductile concrete-crushing failure was observed. When the reinforcement ratio increased to 1.56% and 1.81%, brittle concrete-crushing failure dominated. The incorporation of hybrid fibers improved the ductility and optimized the failure process. Both the hybrid fiber content and the BFRP reinforcement ratio significantly influenced the load-carrying capacity and deformation behavior of the beams. Increasing the fiber content enhanced the cracking load and ultimate load, delayed crack propagation, and reduced crack width, whereas increasing the reinforcement ratio was more effective in improving the ultimate capacity. The load–deflection curves exhibited a typical two-stage response without a yielding plateau. The bridging effect of hybrid fibers effectively mitigated stiffness degradation and improved crack control performance. Moreover, the plane section assumption was validated for hybrid fiber-reinforced BFRP-LAC beams. This study provides a technical basis for enhancing the performance of LAC and promoting the application of BFRP bars in structural engineering.

The combined use of recycled aggregate concrete (RAC) and basalt fiber-reinforced polymer (BFRP) bars offers a promising sustainable and corrosion-resistant solution for reinforced concrete structures. However, the inferior quality of recycled aggregates and the relatively low elastic modulus of BFRP bars can compromise the mechanical and flexural performance of RAC members. To address these issues, hybrid fiber-reinforced recycled aggregate concrete (HFRAC) incorporating polyvinyl alcohol (PVA) and steel fibers was developed, and its mechanical and flexural performances were experimentally investigated. The basic mechanical properties of conventional Portland cement concrete (PC), fiber-free RAC, and RAC with hybrid fiber (HF) contents of 0.6%, 0.9%, 1.2%, and 1.5% were first evaluated. A total of nine beams were subsequently tested under four-point bending to investigate the effects of HF content (0–1.5%) and BFRP reinforcement ratio (0.48–1.98%) on flexural behavior. The results showed that an HF content of 1.2% provided the best performance among the investigated fiber contents at both the material and structural levels. At the material level, compared with RAC, 1.2% HF increased the cube compressive strength, axial compressive strength, elastic modulus and splitting tensile strength by 19.44%, 23.08%, 11.39% and 32.55%, respectively. The incorporation of HF effectively mitigated the mechanical deterioration caused by recycled aggregates, allowing HFRAC to achieve comparable or improved basic mechanical properties relative to RAC. At the structural level, compared with the fiber-free RAC beam, the beam with 1.2% HF exhibited increases of 132.51% and 11.92% in cracking and ultimate loads, respectively, and a 47.9% reduction in crack width, while also demonstrating improved flexural performance compared with the PC beam under the investigated conditions. Three failure modes were observed, namely BFRP bar rupture, balanced failure, and concrete crushing, with balanced failure occurring at a reinforcement ratio of approximately 1.0–1.1%. The hybrid fibers effectively refined cracks through a bridging effect, demonstrating superior crack control compared to increasing the reinforcement ratio alone. This study offers valuable insights into improving the performance of RAC and facilitating the wider adoption of BFRP bars in structural applications.

This study investigates the mechanical properties and uniaxial compression behavior of nano-TiO₂-modified coral concrete (NTCC). Twelve groups of specimens with different nano-TiO₂ contents were prepared and cured in freshwater, seawater, and oxalic acid environments. Cube compressive strength, splitting tensile strength, and uniaxial compression tests were conducted according to relevant standards. The results indicate that nano-TiO₂ significantly enhances the mechanical performance of coral concrete. The compressive and tensile strengths initially increased and then decreased with increasing nano-TiO₂ content, with the maximum strength improvement reaching approximately 22%. Furthermore, increasing the nano-TiO₂ dosage reduced the brittle failure characteristics of NTCC under compression. The curing environment had a significant influence on the performance of NTCC. Specimens cured in seawater exhibited superior early-age strength, whereas those cured in freshwater achieved the highest later-age strength. The stress–strain response of NTCC under uniaxial compression can be divided into three stages: the elastic stage, elastoplastic stage, and descending stage. Based on the experimental results, an empirical constitutive model was proposed for NTCC. The predicted stress–strain curves showed good agreement with the experimental results, demonstrating the applicability of the proposed model for describing the compressive behavior of NTCC.