Influence of micro-cracking on the composite resistivity of Engineered Cementitious Composites

Engineered Cementitious Composites (ECCs) are structural materials known for their excellent tensile ductility and damage tolerance. Previous experimental studies have shown a strong dependence of electrical resistivity of ECC on applied mechanical tensile strain (piezoresistive behavior), which can be potentially utilized for self-sensing mechanical damage for structural health monitoring. In this paper, the influence of micro-cracks on the composite electrical response of ECC under direct tension is investigated experimentally as well as analytically. For this purpose, the electrical-mechanical properties of two ECCs with different crack patterns are compared at macro (composite) and meso (single-crack) scales. An analytical model linking single-crack electrical response and crack pattern of an ECC to its composite electrical behavior is proposed in this study, and verified for both ECCs with experimental observations. Thus, a fundamental understanding of crack patterns and their effects on piezoresistivity of ECC is developed in this study.