Microsilica is a highly reactive pozzolanic material widely known for improving the strength and durability of concrete. In this study, we explored how replacing 10%, 20%, and 30% of cement with microsilica affects the performance of lightweight concrete over 7, 14, and 28 days. The concrete mixes were prepared using a blend of natural and artificial lightweight aggregates with cement content ranging from 350 to 550 kg/m3. To ensure good workability, a 2% modified lignosulfonate-based superplasticizer was used, and water-to-cement ratios varied between 0.30 and 0.45. Along with compressive strength, we also measured the modulus of elasticity, specific weight, and water absorption under both dry and wet conditions. The results clearly showed that higher levels of microsilica led to notable gains in strength and elasticity, while also reducing the weight and water absorption of the concrete. The most effective mix combined 30% microsilica with a cement content above 500 kg/m3, delivering excellent mechanical performance and durability. These findings highlight the potential of microsilica not only to enhance structural quality but also to reduce environmental impact by lowering cement usage. This study supports the thoughtful use of microsilica as a sustainable and performance-boosting material in modern concrete design.
Fallah-Mehrjardi et al. (Wed,) studied this question.