On the strength and pulse velocity of rubberized concrete containing silica fume and zeolite: Prediction using multivariable regression models

Abstract In this study, rubberized concrete containing waste rubber chips, silica fume and zeolite was investigated. For this purpose, coarse aggregates were partially replaced by waste tire rubber, i.e. 10 wt% and 15 wt%. Silica fume and zeolite were incorporated into the binder to replace 10% of the cement. Different mixes were cast and cured in two curing conditions. Compressive strengths of mixes were measured at different ages as 3, 7, 28, and 42 days. Ultrasonic tests were carried out to measure the pulse velocity in different mixes of the rubberized concrete. The relationship between the compressive strength and the pulse velocity was investigated by a power relationship and the coefficients were determined for different mixes. It was observed that strength drops were typically greater in sample without admixtures especially at 28 days of age. It was also found that the pulse velocity could well capture the curing condition and admixtures’ effect on rubberized concrete. Quite high correlations were also observed between the compressive strength and pulse velocity in various mixtures. In order to predict the compressive strengths of the rubberized concrete, different types of multivariable regression models were developed and compared to find the best predictive model for the rubberized concrete. It was found that the full quadratic model was the best model with highest correlation among the assessed regression models.