Statistical analysis of impact strength and strength reliability of steel-polypropylene hybrid fiber-reinforced concrete

This paper statistically investigates the first-crack strength, failure strength, and strength reliability of steel-polypropylene hybrid fiber-reinforced concrete in comparison with the steel fiber-reinforced concrete. The former strengths were measured using the drop-weight test in a batch of 48 discs. The hybrid fiber-reinforced concrete showed smaller variation in the two strengths, although larger scatter in the percentage increase was observed in the number of post-first-crack blows, compared to those of the steel fiber-reinforced concrete. The Kolmogorov-Smirnov test indicates that the two fiber-reinforced concretes hardly followed the normal distributions on the two strengths and the percentage increase. Dunnet's calculations indicate that the hybrid fiber-reinforced concrete provides less significant improvement on the two strengths and the percentage increase than the steel fiber-reinforced concrete. The Kaplan-Meier analysis indicates that the hybrid fiber-reinforced concrete improves a little higher reliabilities of the first-crack and failure strengths than the steel fiber-reinforced concrete. A bi-role failure strength regression model is recommended for the two concretes. (C) 2004 Elsevier Ltd. All rights reserved.