Experimental study on the effect of nano SiO2 dispersion on the compressive strength and early high-temperature resistance of modified cement paste

Abstract

This study investigates the influence of varying levels nano-silica (NS) dispersion levels on cement paste (CP) properties. Utilizing ultrasonic dispersion and water-reducing agent, NS was uniformly dispersed within the CP. This research methodically investigates the dispersion of NS and its subsequent effects on CP's mechanical properties, high-temperature resistance and microstructure. The findings demonstrated that effectively dispersed NS markedly improved CP's initial and residual compressive strength after high-temperature exposure. Optimal comprehensive performance of the cement paste was achieved with an ultrasonic dispersion duration of 40 min, an NS concentration of 1.0 wt%, and Polycarboxylate Ether concentration of 0.75 wt%. The 28-day compressive strength was 83.7 MPa, and the normalized residual compressive strength was 37.3 % after holding at 800 ºC for 2 h. Microstructure analyses indicate that optimal NS dispersion facilitates the early cement hydration process by filling minute voids and increasing the compactness of the cement matrix. This enhancement positively impacts CP's internal structure, mitigating crack formation and growth, thus enhancing compressive strength and high-temperature resilience.