Mix optimization and performance of nano-silica/calcium carbonate modified high-performance concrete

This paper presents a novel approach to reducing cement consumption in concrete by using a combination of nano-silica (NS) and nano-calcium carbonate (NC) as cementitious materials-reducing admixtures (CRA). The innovation lies in the synergistic effect of NS and NC, which not only reduce cement content by 20% but also enhance concrete's mechanical properties and durability. Through a systematic optimization, the combination of 1.751% NS and 0.1% NC was found to significantly improve concrete performance compared to the control mix. Specifically, the 28-day compressive strength increased by 7.9%, the splitting tensile strength rose by 11.8%, and the chloride-ion permeability resistance decreased by 2.7%. Additionally, the optimized mix reduced the concrete cost by 11.17 CNY/ton and decreased CO2 emissions by 27.4 kg/ton. This study provides strong evidence for the practical application of NS and NC in reducing carbon emissions in concrete production, offering an environmentally friendly and economically viable alternative to traditional cement-based mixtures.