Enhancing mechanical performance and crack morphology of engineered cementitious composites through tailoring coral sand

Seawater coral aggregate concrete (SCAC) development has effectively addressed the issues of raw material shortage and construction period delay in the construction of remote islands and reefs. In the present study, seawater coral sand engineered cementitious composites (SCECCs) with characteristics of high tensile ductility and crack control ability are developed by incorporating polyvinyl alcohol fiber. The effects of aggregate type, fineness modulus, and maximum particle size of coral sand on the compressive, tensile, and flexural performance of ECCs are thoroughly investigated. The crack morphology of ECC is quantitatively characterized using digital image processing methods. The tailoring effect of coral particles on ECC's mechanical performance and crack morphologies is specially evaluated. The results indicate that ECC with extra fine coral sand, having a maximum particle size of 2.36 mm, exhibits the highest compressive strength of 63.3 MPa. The reduction in maximum particle size significantly improves the tensile strain-hardening capability of ECC. When coral sand with a particle size below 0.15 mm is incorporated, ECC exhibits excellent tensile properties, with a cracking strength of 2.43 MPa, a tensile strength of 4.29 MPa, an ultimate tensile strain of 5.65 %, and an average crack width of 73 mu m. Seawater coral sand ECC demonstrates a stable development of crack width during the strain-hardening process. A probability density model is established to accurately describe the crack morphology of ECC at arbitrary strains. The modeling results indicate that as fineness modulus and maximum particle size decreases, the probability of forming fine cracks increases, while the occurrence of wide cracks is suppressed.