Enhancing coral aggregate concrete performance via mild acid-washing and fast-setting pre-coating techniques

To promote the quality and utilization efficiency of coral aggregates, an innovative composite modification technique combining mild acid-washing with fast-setting pre-coating is proposed. Utilizing dilute acetic acid as the acid solution, the concentration and immersion duration were optimized by assessing alterations in the physical properties of the coral aggregates pre- and post-treatment. This approach effectively eliminates impurities from the surface layer and interior voids, thereby enhancing the interfacial adhesion between the aggregates and cementitious materials. Additionally, the application of an optimally proportioned sulphoaluminate cement (SAC) slurry as a coating markedly enhanced the strength and reduced the water absorption of the coral aggregates. In comparison to concrete composed of untreated coral aggregates, the composite-modified treatment significantly enhanced the workability and mechanical properties of coral aggregate concrete (CAC). Notably, the slump increased by 38.10 %, while the flexural and compressive strengths improved by 24.77 % and 30.40 %, respectively. These enhancements are ascribed to the gradient filling of pores within the internal weak zones, which elevated the modulus and hardness while markedly reducing the thickness of the interfacial transition zone (ITZ). This study provides a novel strategy for producing high-performance CAC, particularly suitable for marine engineering applications.