Investigation on the shrinkage performance of engineered cementitious composite (ECC) constrained by steel ring

Engineered cementitious composite (ECC) with high amount of cementitious binder exhibits a significant shrinkage behavior, and has a cracking risk under constraint condition in practical engineering. This study investigated the effect of ECC matrix formulation and shrinkage-regulation admixture on the mechanical properties, shrinkage behavior with and without steel ring constraint, and the cracking risks of ECC based on the strength criterion were discussed. The experimental results show that the decrease of water-binder and sand-binder ratio can improve the splitting tensile strength of ECC, but increases the shrinkage of matrix. Excessive substitution of cement by fly ash in matrix has an adverse effect on the strength of ECC, even though the shrinkage evolution of ECC can be effectively inhibited. While a throughout crack is observed in the specimen with insufficient amount of fly ash under steel ring constraint. Moreover, the introduction of expansive agent (EA) and shrinkage-reducing admixture (SRA) is not conducive to the strength development of ECC, which can limit the shrinkage growth. The cracking is taken place in the case of FA-0.67 having cracking risk coefficients Θ _CR less than 1. The constraint degree ψ induced by steel ring is almost independent of ECC mixtures and the traditional strength criterion is not suitable for the assessment of ECC cracking risk, which should consider the material properties and external constraints.