Effects of Activated Fly Ash in Low Ordinary Portland Cement

Swayam Gupta, Harshit Gour

Abstract: This study investigates the effectiveness of various activation strategies- chemical, mechanical, and thermal- for improving the reactivity of fly ash in very low clinker ternary binders. All binders contained 30% OPC, 40% fly ash, and 30% of either metakaolin or limestone as the second supplementary cementitious material (SCM). Compressive strength of mortar cubes was evaluated at 1, 3, 7, 28, and 90 days, and hydration studies were performed using thermogravimetric analysis (TGA) and isothermal calorimetry. Chemical activation was found to provide the highest early-age strength, while mechanical and thermal activations showed more pronounced effects at later ages. The results indicate that the optimal activation strategy depends on the type of co-SCM present in the system, highlighting the importance of multi-SCM design for sustainable low-carbon binders.

Keywords: fly ash activation, supplementary cementitious materials, low clinker binder, compressive strength, pozzolanic reaction