Predicting compressive strength of geopolymer concrete using NDT techniques

Abstract

The present investigation is mainly focused on predicting compressive strength of geopolymer concrete (GPC) using non-destructive testing (NDT) techniques viz., Schmidt rebound hammer (SRH), ultrasonic pulse velocity (UPV) and combined method. The NDT techniques were performed to compare the accuracy between the SRH, UPV and combined method in estimating the compressive strength of GPC. In this study, four mixes of GPC were prepared with different fine aggregate blending. Sand and granite slurry or granite fines (GF) are blended in different proportions (100:0, 80:20, 60:40 and 40:60). Coarse aggregates of size 20 and 10 mm are blended in proportions 60:40. Ground granulated blast furnace slag (GGBS) and fly ash (class F) were used at 50:50 ratio as geopolymer binders. Combination of sodium hydroxide (8M) and sodium silicate solution was used as an alkaline activator. Prior to compressive strength of test specimens, SRH, UPV and combined method were recorded after 7, 28 and 90 days of curing at ambient room temperature. From the results, it is revealed that the compressive strength, SRH, UPV and combined method results were increased up to fine aggregate blending of 60:40. Different equations were proposed correlating the compressive strength of concrete to SRH, UPV and combined method. Statistical analysis includes type of fit, sum of square residuals and standard errors were determined for the proposed equations. The measured compressive strength of all mixes was compared with predicted equations developed by past researchers.