Effect of curing on mechanical strength and microstructure of fly ash blend GGBS geopolymer, Portland cement mortar and its behavior at elevated temperature

The experimental work reported here lay emphasis on mechanical strength, thermal resistance and microstructural characteristics of geopolymer cement to traditional Portland cement prepared under different curing conditions. Portland cement mortars prepared under conventional water curing and air curing aided with 0.5,1, 1.5 and 2.0% dosage (O-1,2,3,4) of poly ethylene glycol (PEG) under different ages. An optimal combination of the PEG has been determined as 1-1.5% with the enhanced the C-S-H gel with better permeability. The strength development of alkali mediated Ground granulated blast furnace slag (GGBS) partially blended with 0, 25, 50, 75% fly ash(FA) (M-1,2,3,4) geopolymer mortars (GPM) prepared under air, water curing and with optimal dose of 1% of PEG. The compressive strength cured under open air and water are compatible that are found to be increased with increase in % GGBS. More than 80% of 28 days(d) strength attained at early ages of 7d in all the GPM samples irrespective of type of curing, suggest that these binders have potential to save time, energy and water that lead to cost economic construction practice. The results on GPM after exposure to elevated temperature 200-600 degrees C show almost retaining the compressive strength while the control of Ordinary Portland Cement(OPC) mortar significantly loses the strength with the development of wider crack width. The microstructural characterization using Scanning Electron Microscope(SEM) analysis indicate that densification of microstructure depends upon curing regime that effect the thermo mechanical strength significantly. (C) 2021 Elsevier Ltd. All rights reserved.