Effect of crystalline admixtures on mechanical, self-healing and transport properties of engineered cementitious composite

Abstract This paper focuses on the effect of chelating crystalline admixtures (CA) on mechanical, self-healing and transport properties of engineered cementitious composite (ECC). Four ECC with varying CA contents were prepared. The effect of CA on the mechanical properties of ECC was evaluated by compressive and tensile tests. The self-healing behavior was investigated by sorptivity test and crack closure behavior. Meanwhile, the water permeability test was adopted to characterize the transport properties of four ECC mixtures. The mercury intrusion porosimetry (MIP) was used to analyze the effect of CA on the pore structure of ECC. The test results show that chelating CA can significantly improve the compressive strength, ultimate tensile strength and transport properties of ECC. Moreover, the addition of chelating CA helps promote the recovery of transport performance and easily restore to the uncracked state. The closure rate and healed width of cracks are increased by CA. The enhancement effect provided by CA has a positive relation with CA content. The analysis of pore structure suggests that chelating CA can improve the pore structure and size distribution. ESEM and XEDS results show that chelating CA helps promote the formation of hydration products, which can enhance the mechanical properties of cementitious materials. The TG results indicate that even if the cementitious materials contain fly ash, chelating CA can accelerate the consumption of calcium hydroxide to form more calcium carbonate, which can improve the self-healing behavior of ECC.