Mechanical properties and microscopic analysis of water-castable engineered cementitious composites (WECC)

To address the difficulties in repairing underwater concrete panels and the unsatisfactory results of existing repair methods and materials, water-castable engineered cementitious composites (WECC) are developed. The effects of flocculant dosage on anti-dispersibility, fluidity, tensile behaviors, flexural behaviors, and fracture behaviors were investigated. XRD, MIP, and SEM tests were conducted on the WECC. Excellent tensile properties, flexural energy absorption capacity, and crack resistance are exhibited by the WECC. The increase in flocculant dosage decreases the dispersion degree during the underwater casting process of WECC, reduces the early hydration reaction rate, increases the internal porosity, resulting in a decrease in various mechanical properties. By comparing the tensile properties of WECC and WECC(L), while integrating microscopic analysis results, the performance loss mechanism of WECC and the tensile constitutive model have been identified. Additionally, the effects of (washed sea sand) sand-colloid ratio on workability and mechanical properties were investigated. When the sand-colloid ratio is 0.25, a higher level of compatibility between the fibers and the matrix is observed, and good ductility is demonstrated. Considering various performance factors, two mixed proportions have been established. The time, resources, and labor required for the repair process can be significantly reduced by using WECC for repairing underwater components, and the hydraulic structures can operate normally. The externally generated complex stress can be effectively released by WECC. The tested results provide crucial references for the underwater reinforcement of WECC.