Effects of silica fume and rice husk ash contents on engineering properties and high-temperature resistance of slag-based prepacked geopolymers

Geopolymer slurries can be favored to achieve a sustainable approach in prepacked aggregate concretes. This study presented here investigated experimentally the effect of silica fume (SF) and rice husk ash (RHA) on the high-temperature resistance of slag-based sustainable prepacked geopolymers. In the production of prepacked aggregate geopolymers (PAGs), ground granulated blast furnace slag (GGBFS) was utilized as the main aluminosilicate-rich precursor material, and SF and RHA were replaced with GGBFS in various contents including 7.5 % and 15 %. The physical, mechanical, and microstructural properties of specimens cured at 35 °C and 70 °C for 8 h were determined comparatively. Residual compressive strength and mass loss of mixtures exposed to elevated temperatures (150 °C, 300 °C, and 600 °C) were determined to observe high-temperature effects. The results revealed that the properties of PAGs were affected considerably by curing temperature and precursor type. The maximum oven-dry density of 2244 kg/m3 with RHA content of 7.5 % was obtained at 70 °C curing temperature. Specimens produced with RHA tended to absorb more water under both heat curing conditions and the highest water absorption of 10.2 % with RHA content of 7.5 % was obtained at 35 °C curing temperature. The compressive strength of PAGs varied between 13.7 and 28.10 MPa, and flexural strengths varied between 1.48 and 2.74 MPa. Increasing curing temperature improved the strength properties of PAGs, and in general, the 8-h compressive and flexural strength values of SF samples were relatively higher. The application of elevated temperature to the PAG mixtures caused a significant reduction in both compressive strength and mass loss. Among the specimens cured at 35 °C, the specimens with RHA showed relatively better high-temperature performance in terms of compressive strength, while the specimens with SF cured at 70 °C showed better performance. PAG specimens produced with RHA showed the best high-temperature performance against mass loss. According to the results obtained in the given study, these recycled wastes could be used to improve the physico-mechanical properties and high-temperature performance of slag-based PAGs.