Statistical and experimental study to evaluate the variability and reliability of impact strength of steel-polypropylene hybrid fiber reinforced concrete

This paper presents the statistical and experimental study on the variability and reliability of impact strength of steel- polypropylene Hybrid-Fibre reinforced Concrete (SPHFRC) by using a simple drop weight test recommended by ACI committee 544. The experimental findings show that hybridization of polypropylene-steel fiber leads to improvements of both the mechanical properties and the impact resistance of concrete when compared to its mono fiber counterpart. The normality test was carried out on first crack strength (N1) and failure strength (N2) using a distribution plot and its accuracy was verified with the Kolmogorov-Smirnov test. The improvement in the impact strength of SPHFRC discs (control group) over mono FRC discs at a 95% confidence level on the results of the impact test was assessed employing Dunnet's calculation. The failure lifetime reliability analysis for impact strength of different FRC was assessed using the non-parametric procedure. Moreover, by using the regression technique, linear relationships between the first crack and failure strengths for all the FRCs mixes were proposed. The strength prediction models proposed in this study performs very well with the data set of previous researchers.