Matrix design of light weight, high strength, high ductility ECC

In the past decade, the research on high strength, high ductility engineered cementitious composites (HSHD-ECC) has drawn much attention worldwide. However, due to the high matrix toughness associated with HSHD-ECC, saturated multiple cracking phenomena was rarely observed, hence hindering its robustness and high strain capacity. In this paper, ECC mixtures with relatively weak matrix were designed to allow much more cracks to be initiated, meanwhile retaining features of high strength, high ductility as well as light weight. The experimental results showed that ECC mixtures with addition of air entraining agent (AEA) increases the compressive/tensile strength slightly, while adding light weight filler (LWF) materials into ECC mixtures show the opposite tendency. However, all ECC mixtures exceed 60 MPa in compressive strength that satisfy the requirement of high strength concrete. In addition, incorporating AEA and LWF materials into HSHD-ECC lowered its matrix toughness and density effectively, as a result, increased its strain capacity and extent of saturated cracking significantly. In particular, the strain capacity of HSHD-ECC with addition of fly ash cenosphere (FAC) could reach 12.5%. At micro scale level, the fiber/matrix interfacial frictional bond was altered with the matrix design in HSHD-ECC, and the experimental findings well explained the change tendency in tensile strength of five ECC mixtures based on micromechanics theory. (C) 2019 Elsevier Ltd. All rights reserved.