Durability of alkali-activated slag concrete incorporating silica fume and rice husk ash

To improve the mechanical properties and durability of alkali-activated slag concrete (AASC), as well as to reduce carbon emissions and exploitation of natural resources. This paper attempts to introduce rice husk ash (RHA) and silica fume (SF) into the AASC system. The effects of RHA and SF on the physical properties (water absorption and density), mechanical properties (flexural strength and compressive strength), and durability properties (dry shrinkage, resistance to sulfuric acid attack and carbonation) of AASC are examined. The optimization mechanisms are also explored from the points of pore structure and microstructure analysis. The experimental results suggest that RHA and SF can substantially reduce water absorption and improve the mechanical and durability properties of AASC. Remarkably, adding 10 wt% RHA into concrete can reduce the water absorption by 42%, increase the strength by 9.7–20%, the resistance to sulfuric acid attack by 26.91%, and the resistance to carbonization by 54.4%. Unfavorably, its dry shrinkage increases by 3.2–33%. Microstructural investigations demonstrate that the addition of RHA and SF to the AASC system provides an additional source of silica, which could have a filler effect, pore refinement, and pozzolanic nature. Moreover, RHA has more silica content than SF, and the particle size of RHA is finer and the reaction is more adequate, so the effect is more remarkable. The findings of the study suggest that RHA and SF demonstrate promising prospects in improving the durability and sustainability of AASC.