Improvement of Mechanical Properties and Condensation Behavior for Alkali-Activated Materials by Sodium Silicate

Abstract

To further enhance the compressive strength of alkali-activated materials and reveal their condensation behavior, the reactivity of alkali-activated slag materials was enhanced through the addition of different kinds and proportions of sodium silicate. The mechanical properties of the specimens were observed regularly and the condensation behavior was further analyzed. The results showed that both solid and liquid sodium silicate could significantly improve the compressive strength. The maximum increase in compressive strength was 123.7%, while the initial and final setting times were significantly shortened to 9 min. When solid sodium silicate content increased from 5% to 15%, the compressive strength first increased to 34.6 MPa and then decreased to 28.6 MPa, indicating that 10% was the optimum solid sodium silicate content. The large amount of crystallized solid sodium silicate in the specimen led to the decrease in mechanical properties. When liquid sodium silicate content increased from 5% to 15%, the compressive strength first increased to 52.8 MPa and then tended to be stable, implying that 10% was the optimum content. This shows that its reinforcement effect has a maximum limit. The activation effect of liquid sodium silicate was better than that of solid.