Strengthening the performance of limestone-calcined clay cement (LC3) using nano silica

Limestone-calcined clay cement (LC3) is a promising cementitious material for the future; however, it poses the problem of low strength in the early stage, which has not yet been solved. This research proposed to increase the performance of LC3 through nano silica, especially its early strength and carbonation resistance. The effects of adding 1% and 2% nano silica on the compressive strength, hydration reaction, microstructure, electrical resistivity, and carbonation resistance of LC3 mixtures were investigated. The experimental results indicated the following: (1) nano silica can significantly improve the compressive strength of LC3 mixtures, especially the - day compressive strength; (2) the results of isothermal calorimetry and thermogravimetric analysis showed that nano silica can significantly accelerate the reaction rate of LC3 mixtures; (3) with the addition of nano silica, the resistivity and ultrasonic pulse velocity of the LC3 mixtures increased significantly, and the carbonation resistance was improved, indicating that nano silica can refine its microscopic pore structure and enhance its durability. In general, the addition of nano silica provides the feasibility to overcome the weaknesses of LC3 concrete (such as low early age strength and low carbonation resistance), enhance the long-term performance, and extend the service life.