Strength, workability, and setting time of alkali-activated cement at ambient curing

Ordinary Portland Cement (OPC) 's success comes at a risk to the environment due to the carbon dioxide emissions associated with its production. This has led the scientific community to look for alternative building materials with lower environmental impact. Alkali-Activated Cement (AAC) is an excellent alternative. Various types of AAC concrete have been investigated; however, most of these studies focus on heat-cured AAC mixture, mainly investigating mechanical behaviors. The construction industry is not only looking for environmentally friendly concrete but also convenience and flexibility. AAC at ambient curing conditions is a preferable binder with wider applications. The use of ground granulated blast furnace slag (GGBS) is common when targeting ambient curing behaviors. GGBS, however, reduces the setting time and flowability of the concrete. In this study, the effect of binder content, alkaline solid to binder ratio (AS/B), sodium silicate to sodium hydroxide solids ratio (SS/SH), and total water to total binder solid (TW/TS) ratio on strength, setting time and flowability of AAC concrete is studied. Binder content was varied from 550 kg/m³ to 750 kg/m³, AS/B ratio from 0.14 to 0.22, SS/SH ratio from 1.5 to 2.5 and TW/TS ratio from 0.29 to 0.39. The results showed that the increase in binder content increased both setting time and flowability. AS/B ratio has an opposite effect on strength and setting time and flowability, while the increase in SS/SH ratio decreased setting time and increased flowability. Understanding these behaviors is of paramount importance in the design of a suitable concrete mixture.