Improvement of early strength of fly ash-slag based one-part alkali activated mortar

•Increasing slag content increase the early compressive strength but reduced flexure strength and workability.•Surficial cracking is induced if slag content is high or retarder content is reduced.•Increase in curing temperature led to significant improvement in early strength.•Later age strength was somewhat independent of curing temperature.•Microstructural testing affirms that heat curing does not significantly alter the structure of mix but only accelerates the rate of reaction. One-part Alkali activated material (AAM) is eco-friendly replacement of OPC with adequate strength and durability characteristics. In this study, the impact of slag content, activator dosage, retarder content and curing temperature was evaluated on fresh and early-age mechanical properties of one-part fly ash/slag-based alkali activated mortar. For assessing the effect of curing temperatures, three temperatures were selected: 20 °C low ambient temperature, 35 °C high ambient temperature and 65 °C replicating heat curing. Consistency, setting time, mix temperature and pH measurements were recorded for fresh mix using standard procedures. In addition, hardened mortar specimens were tested for compressive and flexure strength in conjunction with microstructural characteristics (SEM, XRD, and FTIR analysis). The test results depicted that among all parameters, curing temperature governed the development of early age strength of one-part AAM mortar. Microstructural testing confirmed the enhancement of the geopolymerization reaction through heat curing thus leading to a substantial increase in the early strength.