Effect of Sodium Hydroxide Molarity on the Properties of Metakaolin-Eggshell-Based Geopolymer Cured at Ambient Temperature

Geopolymer is a novel form of concrete with the exclusion of cement completely. It is produced from the reaction of aluminosilicate material and alkaline activators. The commonly adopted methods of curing geopolymer concrete are oven curing, ambient curing, steam curing. It has been discovered that oven curing provides higher mechanical strength. However, oven curing method is limited to precast structures, in other to develop a geopolymer concrete which will be able to set at ambient condition, small amount of calcium-rich material can be used like slag, eggshell powder (ESP). For this research, ESP is used together with metakaolin due to it richness in calcium which responsible for setting of concrete in OPC, its availability, and the threat it poses to the environment due to improper disposal. The alkaline activators bind the unreacted materials together and produce sodium aluminosilicate hydrate (NASH), the major compound for strength development. However, in oven cured method, higher molarity of sodium hydroxide results into higher compressive strength, there is reduction is strength when there is excess sodium in the mix which can react with CO2 present in the atmosphere and lead to carbonation which can lead to deterioration of the concrete. Metakaolin is replaced by 0, 10, 20 and 30% ESP. It was discovered that ESP has a substantial effect on the mechanical and durability performance at ambient temperature at 14 M, and there is reduction of strength at 16 M.