Effect of sub-elevated temperature on mechanical properties of ECC with different fly ash contents

Abstract

In this paper, the mechanical properties of Engineered Cementitious Composites (ECC) with two different fly ash contents after sub-elevated temperature exposure were investigated systematically at multiple scales. At composite level, uniaxial compressive and tensile tests were performed on specimens underwent 20 °C, 50 °C, 100 °C, and 200 °C exposure. The results indicate that, as temperature rise from 20 °C to 200 °C, the compressive strength of both ECC mixtures increased due to the refinement of the matrix pore structure. In term of tensile properties, after exposed to 100 °C and 200 °C, ECC M1 with relatively lower fly ash content shows a substantial reduction in strain capacity, but still retaining strain-hardening behavior, whereas ECC M2 with higher fly ash content exhibits a comparable or even enhanced tensile strength and strain capacity. At micro-scale, ECC matrix toughness was increased and PVA fiber strength was degraded under 200 °C exposure, which deteriorates the tensile properties of ECCs. However, the above negative effects are diminished due to the reduced fiber/matrix interfacial bond. Furthermore, the rather low matrix toughness and fiber/matrix interfacial bond associated with high fly ash content are the main reasons for the highly remained ductility in ECC M2 after sub-elevated temperature exposure.