Performance Improvement and Design of UHDMC Using Fly Ash and Silica Fume

This chapter endeavored to create an ultra-high ductility MPC-based composite (UHDMC) utilizing fly ash (FA) and silica fume (SF). An initial macro-mechanical examination of UHDMC revealed significant enhancements in both ultimate tensile stress and strain when 30% FA and 20% SF substitutions for MPC were applied. Remarkably, an optimized mix of FA and SF enhanced both the ultimate tensile stress and strain. Subsequent investigation into micro-mechanical behavior of UHDMC led to the calculation of stress-based and energy-based pseudo strain hardening indices ( \(PSH_{\sigma }\) and PSHJ, respectively). It emerged that for UHDMC, both \(PSH_{\sigma }\) and PSHJ increased with growing proportions of SF or FA substituting MPC. Application of FA, in contrast to SF, resulted in comparable \(PSH_{\sigma }\) but a superior PSHJ. Moreover, employing a mix of FA and SF yielded substantial enhancements in \(PSH_{\sigma }\) and PSHJ, with the F30 + S10 mixture found to be the most effective. From these findings, a numerical connection was established between pseudo strain hardening indices and ultimate tensile strain, serving as a roadmap to design UHDMC to a desired ultimate tensile strain. Notably, to achieve UHDMC with ultimate tensile strains up to and beyond 3%, both \(PSH_{\sigma }\) and PSHJ must collectively exceed 2.2 and 26.7, respectively.