This research advocates for the use of basalt fiber-reinforced polymer (BFRP) bars and recycled tire steel fibers to reinforce concrete beams. Six concrete beams were constructed using different volume contents of recycled tire steel fibers (0, 0.5%, 1.0%, 1.5%) and BFRP reinforcement ratios (0.48%, 0.75%, 1.08%). Mechanical properties tests were conducted to investigate the flexural characteristics and failure modes of beams utilizing the non-contact full-field strain displacement measuring technology–digital image (3D-DIC) technology. The recycled tire steel fiber (RTSF) improves flexural performance, which contributes to inhibiting crack propagation, reducing flexural deformation, and improving the first cracking and ultimate loading capacities. Under the same reinforcement ratio, in comparison to ordinary BFRP beams, the cracking load of BFRP-RTSF beams increased by 17.73%, 23.76%, and 42.94%, respectively, and the ultimate bearing capacity increased by 4.03%, 5.85%, and 13.21%, respectively. In addition, a modified calculation model of bearing capacity considering RTSF tensile strength is proposed. The predicted values of BFRP-RTSF beams match well with the experimental values.

Coral aggregate concrete (CAC) serves as a critical material for sustainable development in marine engineering, effectively addressing the shortage of aggregate resources in the construction of offshore islands and reefs. In this paper, the aggregate characteristics, static and dynamic mechanical properties and modification technology of CAC are systematically reviewed. Research indicates that the coral aggregates (CAs), due to its high porosity (approximately 50%), low bulk density (900–1100 kg/m³), and rough, porous surface, results in relatively low static compressive strength (20–40 MPa), insufficient elastic modulus, and significant brittleness in CAC. However, its dynamic performance shows the opposite advantage. Under impact loads, the energy absorption capacity is enhanced by 32.6–140.3%, compared to ordinary concrete (OC) due to the energy dissipation mechanism of pore platic deformation. Through the modification techniques, such as aggregate pre-treatment (acid washing/coating), incorporation of auxiliary cementitious materials (silica fume increases strength by 16.4%), fibre reinforcement (carbon fibres enhance flexural strength by 33.3%), and replacement with novel cementitious materials (magnesium sulphate cement improves chloride ion binding capacity by 90.7%), the mechanical properties and durability of CAC can be significantly optimised. This paper highlights gaps in current research regarding the high strain rate (>200 s⁻¹) dynamic response, multi-factor coupled durability in marine environments, and the engineering application of alkali-activated materials, providing theoretical basis for future research directions.

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.