Effect of silica fume on Self-compacting Earth Concrete: Compressive strength, durability and microstructural studies

Abstract

In this study, the effects of the combination of clay and cement, as well as the synergistic effect of silica fume with clay and cement were investigated. Firstly, the focus was on determining the optimal combination of different percentages of silica fume (7.5 %, 10 %, and 12.5 %) and clay (50 %, 60 %, 70 %, and 80 %) content by wet and air curing conditions to increase the compressive strength of paste mixtures. Then, the optimal mixture design was selected for the production of concrete samples, and subsequently, the mechanical properties, chloride migration, accelerated carbonation and microstructure analysis were investigated. The results show that the compressive strength of concrete samples containing 50 % clay as a cement (C50) replacement is 59.81 % and 68.13 % lower than that of the control concrete at 28 and 90 days of aging, respectively. On the other hand, the mixture containing 50 % clay and 10 % silica fume (C50S10) improved the compressive strength by 28.08 % in 28 days and 35.18 % in 90 days compared to the mixture containing 50 % clay. At the age of 90 days, the depth of carbonation penetration in C50 mixture was 22.7 mm. In contrast, the C50S10 mixture's carbonate depth after 90 days was 36.7 % lower than that of the C50 mixture. The microstructural analysis demonstrates that the presence of a silica compound in silica fume results in the production of CSH, thus improving the denser mixture. This study suggests using silica fume in combination with earth concrete can be a viable solution to enhance mechanical strength and durability.