Development of a Statistical Model for Strength Prediction of BA-GGBFS-FS Geopolymer Concrete Paver Blocks

Geopolymers, an alternate class of binders which is a cementless one has emerged in the recent decades to replace cement. Geopolymers invented by Joseph Davidovits in 1978 were initially developed to serve as a fire resistant material, but it has now gained momentum as an effective alternate to cementitious binders to limit greenhouse gas emissions. In view of the environmental degradation caused by the cement industry and indiscriminate sand mining, an attempt has been made in this research work to develop geopolymer concrete using Bottom ash, GGBFS which are industrial by products as replacement for cement and Foundry sand, a by product from the foundries as replacement for natural sand and to assess their strength and durability properties.

Multiple regression analysis was used for identifying the relationship between the variables, molarity, mix ratio and density on compressive strength of geopolymer concrete. Compressive strength was taken as the dependant variable and molarity, mix ratio and density were taken as the independent variables. Stepwise method of multiple regression was carried out to identify the extent to which each of the parameters influences the compressive strength of geopolymer concrete. It was observed that molarity and mix ratio were found to be statistically significant when compared to the density. On the whole, the model was statistically significant and accounted for approximately 93% of the variance in compressive strength. Molarity received the strongest weight in the model followed by the Mix ratio. With the sizeable correlations between the predictors, the unique variance explained by molarity was 64% and that by mix ratio was only 21%. The regression coefficients were used to construct an Ordinary Least Squares (OLS) equation. Separate equations were developed for M30, 35, 40, 50 and 55 grades of Geopolymer concretes and was validated with the experimental results.