Mechanical properties and constitutive modelling of engineered cementitious composites made with waste concrete powder

Abstract

The feasibility of producing engineered cementitious composites (ECCs) by partially replacing fly ash (FA) with waste concrete powder (WCP) was investigated and an improved tensile constitutive model was developed. ECC specimens with different WCP substitution rates were prepared, and their mechanical properties, tensile behaviour, fracture parameters and microstructure were systematically evaluated. To overcome the limitations of the classical bilinear tensile model in describing strain-hardening, a ‘linear & curvilinear’ constitutive model (L&C model) based on a sigmoid function was developed. The results show that WCP enhanced hydration through nucleation and micro-filler effects, thereby improving mechanical performance and strain-hardening capacity. The optimal substitution rate was found to be 75%, yielding a tensile strength of 4.1±0.28 MPa and an ultimate tensile strain of 4.0±0.42%. The proposed L&C model showed excellent agreement with experimental tensile curves, with correlation coefficients exceeding 96%. The results confirm that WCP is a viable alternative to FA for ECC production and that the proposed L&C constitutive model provides a more accurate description of tensile strain-hardening behaviour.