The importance of using silica fume and pumice powder in cement-based fiber composites, with a focus on microstructural and mechanical assessments
Soroush Rashidi, Mohammad Maghsoudi, Mitra Manouchehri, Mahdi Bameri, Hocine Siad, Mohamed Lachemi
Abstract
This study aims to evaluate the combined effect of pumice powder and silica fume, used as a binary supplementary cementitious material (SCM) blend, on the microstructural, mechanical, and pull-out properties of steel fiber-reinforced cementitious composites. Concrete cylinders and prisms were prepared with varying steel fiber contents (0.5–1.5 %) and binary SCMs (10 % silica fume combined with 10 % or 20 % pumice powder). Experimental tests were conducted to determine compressive strength, tensile strength, flexural strength, modulus of elasticity, Poisson’s ratio, and bond behavior through steel rebar pull-out tests. Microstructural analyses included FTIR, XRD, TG/DTG, and field emission scanning electron microscopy (FESEM). The results demonstrated that the optimal mixture, containing 20 % pumice powder and 10 % silica fume, significantly enhanced the compressive strength by up to 120 %, the modulus of elasticity by 17 %, the flexural strength by up to 68 %, and the pull-out resistance by up to 73 % compared to the control sample. Additionally, this blend improved the pore-filling effect, promoted the consumption of portlandite, and facilitated the formation of C-S-H/C-A-S-H phases, thereby confirming the positive effect of pumice powder and silica fume on the performance of steel fiber-reinforced cementitious composites.