Investigation of properties of mortar containing pyrogenic silica-added supplementary cementitious materials

This study investigated the effect of supplementary cementitious materials (SCMs) with pozzolanic nature fly-ash (FA), silica fume (SF), and ground granulated blast furnace slag (GGBFS) on the properties of cement mortar with pyrogenic silica addition. First, standard reference (SR) samples were prepared using CEM I 42.5 R-type cement. Pyrogenic silica was added to cement (0.5% by weight) to prepare another group of reference (PR) mortar samples. Cement in PR mortars was replaced with FA, SF, and GGBFS up to 10, 20, and 30%. The mortar samples were placed in 40x40x160 mm metal molds using a vibrating table. The following day the samples were removed from the molds and water cured for 7, 28, and 90 days. The results showed that increases in curing times helped improve the mechanical properties of the mortars. Moreover, the physical properties of PR mortars were affected more positively than the SR mortars. SF-substituted mortars had highest compressive strength, followed by GGBFS- and FA- substituted mortars. In conclusion, pyrogenic silica contributed to some extent to early strength, followed by a decrease.