Microstructure-based prediction of UHPC's tensile behavior considering the effects of interface bonding, matrix spalling and fiber distribution

Abstract

Ultra-high performance concrete (UHPC) is an ideal construction material to cut down carbon emissions due to its superior mechanical performance and durability. It is important to clarify the relationship between the microstructure and the overall tensile response of UHPC. In this paper, a microstructure-based multiscale framework is proposed to predict the stress-strain curve of UHPC under tensile load. The linear elastic stage is obtained by estimating the effective properties with the multi-level homogenization scheme based on the microstructure. The strain hardening and tension softening processes in the tensile curve are predicted with a statistical micromechanical damage model, where the characteristics of steel fibers are considered, including the effects of slip-softening, residual bonding strength of the fiber/matrix interface, matrix spalling and fiber orientation distribution. Comparisons with existing test results and previous models demonstrate the feasibility of using this multiscale framework to predict the overall tensile response of UHPC, especially the tension softening branch. Finally, the effects of interface parameters, matrix spalling degree, fiber orientation distribution, hydration degree and water/binder ratio on the tensile response of UHPC are evaluated and discussed with the proposed framework.