Porous concrete modification with silica fume and ground granulated blast furnace slag: Hydraulic and mechanical properties before and after freeze-thaw exposure

Abstract

This study investigates the effects of incorporating silica fume (SF) and ground granulated blast furnace slag (GBFS), both individually and in hybrid combinations, on various properties of porous concrete (PC) were evaluated under room conditions and after freeze-thaw (F-T) cycles. The hardened density (HD), water permeability coefficient (k), apparent porosity (AP), as well as compressive strength (CS), splitting tensile strength (STS), and flexural strength (FS) at 7, 28, and 120 days. Additionally, the impact of SF and GBFS on the mass loss (ML), residual compressive strength (RCS), residual splitting tensile strength (RSTS), and residual flexural strength (RFS) of PC samples subjected to 30, 60, 120, and 180 freeze-thaw (F-T) cycles was analyzed. The findings revealed that the addition of SF and GBFS decreased the AP and k values of PC samples under room conditions. Furthermore, these materials significantly improved the CS, STS, and FS properties of PC samples, especially at the 28-day and 120-day marks, owing to their enhanced pozzolanic activity over time. SF and GBFS also contributed to higher RCS, RSTS, and RFS values in PC samples after F-T cycles compared to the control samples. This was due to their effective gap-filling properties and the formation of additional calcium-silicate-hydrate (C-S-H) gels within the matrix. Additionally, SF and GBFS led to slightly higher RDME values in the C1-C6 samples than in the control samples following F-T cycles. However, SF and GBFS did not have a significant impact on reducing the ML values of PC samples after F-T cycles.