Effect of pore structure properties on strength properties of hybrid silica fume mortars containing randomly distributed carbon fibers

Investigating the changes in pore structure features caused by fiber inclusion is crucial with respect to comprehending the beneficial use of fiber in calcium silicate structure. This study focused on the relationships between pore structure features and mechanical properties in carbon fiber (CF)-incorporated hybrid silica fume (HSF) mortars. For this purpose, randomly distributed fiber-incorporated silica fume (SF) mortar mixtures containing 0%, 0.15%, 0.3%, 0.45% and 0.6% CF in weight basis were prepared and the effects of CF inclusion on pore structure features were investigated. The results indicated that CF inclusion deeply affects the gel pore formation and pore area characteristics of HSF cement matrix. Based on the pore modification effect, the volume of pores in pore sizes between 10–100 and 550–800 nm showed great influences on the compressive strengths of HSF mortars with R2 of 0.93 and 0.95 at 7- and 28-day samples, respectively. In addition, 7- and 28-day flexural strengths could be predicted by the measurement of critical pore contents (in pore sizes between 3–10 and 1000–10,000 nm, respectively) with correlation coefficients of 0.97 and 0.90, respectively. This work provides an innovative approach by addressing the critical pore contents for strength prediction in fiber-incorporated HSF samples. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.