Early structural build-up, setting behavior, reaction kinetics and microstructure of sodium silicate-activated slag mixtures with different retarder chemicals

The utilization potential of citric acid, sodium tetraborate decahydrate and sodium triphosphate pentabasic to control fresh state properties of sodium silicate-activated alkali-activated slag cements (AASC) has been studied. The early structural build-up, reaction kinetics, pore solution chemistry, setting behavior, and hardened properties such as microstructure, pore structure, and mechanical properties of AASC with these chemicals were investigated. Test results showed that early structural build-up, reaction kinetics and setting behavior of AASC can be well controlled by using these chemicals. The citric acid was found the most effective admixture to prolong the setting times of AASC; however, it caused a dramatic decrease in mechanical properties. On the other hand sodium triphosphate pentabasic could provide a slight delay in setting times, while sodium tetraborate decahydrate prolonged the setting times significantly without any detrimental effect on the mechanical properties.