Behavior of low-calcium fly and bottom ash-based geopolymer concrete cured at ambient temperature

This paper presents the results of an experimental study on the behavior of fly ash-, bottom ash- and blended fly and bottom ash-based geopolymer concrete (GPC) cured at ambient temperature. A total of 10 bathes of GPC and a single batch of ordinary Portland cement concrete (OPC) were manufactured. The tests of compressive strength, elastic modulus, flexural strength, workability, drying shrinkage and absorption capacity were carried out to determine the properties of fresh concrete and mechanical and durability-related properties of hardened concrete. Test parameters included the mass ratio of fly ash-to-bottom ash, liquid alkaline-to-coal ash binder ratio, coal ash content and concrete type. The results indicate that the selected parameters significantly affect the microstructure and the behavior of GPCs. It is seen that bottom ash-based GPCs exhibited significantly lower geopolymerization than that of the fly ash-based GPCs, resulting in the inferior behavior of the former compared to the latter.