Tailoring strain-hardening behavior of high-strength Engineered Cementitious Composites (ECC) using hybrid silica sand and artificial geopolymer aggregates

Hybrid artificial geopolymer aggregates (GPA) and natural silica sand were used to strategically tailor the tensile strain-hardening behavior of high-strength engineered cementitious composites (HS-ECC). With such hybridization, the weaknesses of GPA (i.e., relatively low strength and stiffness) were utilized in the performance-based design of HS-ECC, while the advantages of GPA were retained (e.g., the utilization of industrial by-products/wastes through chemical activation and conservation of natural resources). In this study, a comprehensive experimental program was conducted at multiple scales on the HS-ECC. It was found that increasing the replacement ratio of silica sand by GPA improved the tensile ductility, crack control ability, and energy absorption of HS-ECC, although its compressive and tensile strengths were reduced. GPA with low alkalinity were observed to react with the cementitious matrix, and the pozzolanic reaction provided additional chemical bond and thus enhanced the GPA/matrix interface. In addition, GPA could be regarded as “additional flaws” in the HS-ECC system. According to the Weibull-based modeling, it was found that GPA could play a crack-inducing role in activating more inactive initial flaws. Therefore, GPA can tailor the active flaw size distributions in HS-ECC matrix. The findings of this study provide a new avenue for the utilization of GPA.