Effects of citric acid on the rheology, hydration and strength development of alkali aluminosilicate cement

Alkali-activated aluminosilicate cements, as a sustainable and high-performance class of cementitious materials, can benefit from the development of admixtures that can enhance various aspects of their performance. Alkali activation generally occurs at a faster pace than the hydration of Portland cement (PC). In this investigation, citric acid was evaluated as an admixture for controlling the hydration kinetics, enhancing the fresh-mix rheology and delaying the setting of alkali aluminosilicate cement (AAC) without compromising its long-term strength. The obtained experimental results showed that the use of 3 wt% citric acid reduced the heat of hydration, improved the fresh-mix rheology and increased the hardened material compressive strength of the AAC. The results demonstrate the merits of using citric acid as an effective admixture in alkali-activated cement to make it more compatible with the construction practices established for PC.