Influence of molarity and alkali mixture ratio on ambient temperature cured waste cement concrete based geopolymer mortar

Abstract

Generation of an enormous amount of construction and demolition (C&D) waste due to rapid growth in the infrastructure segment globally is a matter of dire concern for the present decade due to poorly managed disposal to re-utilization. The present study focuses on the formulation of an effective utilization regime of C&D waste (cement concrete) for its re-consumption as geopolymer mortar. Formulation of different molarities of sodium hydroxide (6 M to 16 M) and alkali mixture ratio of sodium silicate to sodium hydroxide solution (1.5, 2.5 and 3.5) have been done and cured for 90D at controlled ambient temperature. The samples were tested for fresh and hardened properties. The effect of silicate modulus and Na2O% with different alkali proportions on the hardened properties were studied. The results reveals that the optimum compressive strength of 20.7 MPa is achieved at a silicate modulus of 1.54 and Na2O% of 12.5%. Further microstructural analysis (mineralogical, elemental, thermal and bonding types) has been done to better comprehend the interactive performance of C&D waste with the change in alkali quantities. The physicochemical and microanalysis reveals that molarity, dissolution of aluminosilicates, and mineralogical compositions are the main factors governing the outcomes while keeping the curing regime at ambient temperature.