Excavated soil waste as fine aggregate in fly ash based geopolymer mortar

To explore the significance of geopolymer technology on producing environmental friendly waste based mortar which could be a sustainable replacement for conventional mortar; Low, medium and high plastic soil from different locations was used as fine aggregate to produce fly ash based geopolymer mortars. The experiments were designed using central composite design of response surface methodology. Molarity of NaOH, curing temperature and fly ash content were the key parameters considered in this study. The interaction effect of these parameters with four different fine aggregates (river sand, low, medium and high plastic soils) were identified and discussed. It is demonstrated that geopolymerisation helps in utilizing even high plastic soil as fine aggregate in construction applications. Soil based geopolymer mortar resulted in lower density range compared to conventional geopolymer of similar strength values. The test results show that strength and shrinkage properties of soil based geopolymer mortar significantly depends on the type of clay present in the soil. Geopolymer mix with each specific soil has an optimum combination of NaOH, curing temperature and binder dosage that helps them achieve the desired properties such as higher compressive strength and lower dry density, water absorption and shrinkage values.