Abstract : Geo-polymer composites are emerging as sustainable replacement options of conventional cement concrete, for effective reduction in carbon footprint. Owing to the use of supplementary cementitious materials viz. fly ash, GGBS, metakaolin, brick husk ash and their combinations, the resulting concrete is different from the conventional concrete in terms of fineness, density, packing etc. Hence, the correlation equations used to derive compressive strength values from non- destructive test results,