Mechanical properties and microstructure evolutions of alkali-activated slag materials subjected to centrifugation with different rotation rates

This paper studies the effect of centrifugation rotation rate on the compressive strength and microstructure of alkali-activated slag (AAS) paste. The results indicate that the compressive strength gradually improves with increase in centrifugation rotation rate and the maximum compressive strength is 71.8 MPa at 5000 rpm with increasing amplitude of 133.8% compared to the AAS paste without centrifugation. The flower clusters gels of C(N)-A-S-H including large proportion of N-A-S-H appear in the AAS paste with centrifugation rotation rates of 0 r/min. The layered gels mainly including the hydrotalcite phase and C(N)-A-S-H are found under the centrifugation rotation rates of 1000 r/min. The globule gels of C-A-S-H including small proportion of N-A-S-H appear in the AAS paste with centrifugation rotation rates of 3000 r/min and 5000 r/min. The more generation of large size globule gels of C-A-S-H is conducive to improving compressive strength of AAS paste. Furthermore, the increase in centrifugation rotation rate promotes the reaction of slag and generation of gel products, and improves the polymerization and cross-linking degree of gel products, causing the lower porosity and higher bulk density, eventually leading to the enhancement of compressive strength.