Loading Rate Effect on the Fracture Behaviour of Three Different Steel Fibre-Reinforced Concretes

Abstract

Three-point bending tests on notched beams of three types of steel fiber-reinforced concretes (SFRC) have been conducted using both a servo-hydraulic machine and a drop-weight impact instrument. These three different concretes had the same matrix, while various fiber contents and deflection (displacement) hardening or softening behaviours, i.e., 40 kg/m 3 Dramix OL 13/0.20 (Concrete PA), 40 kg/m 3 Dramix OL 13/0.20 + 20 kg/m 3 Dramix RC 80/30 BP (Concrete PB) and 40 kg/m 3 Dramix OL 13/0.20 + 60 kg/m 3 Dramix RC 80/30 BP (Concrete PC), respectively. The shape and geometry of the specimen followed the RILEM recommendation but with a reducing factor 1.5. The flexural strength and the fracture energy were measured over a wide range of loading rates (displacement rates), spanning six orders of magnitude, from 2.20 ×10 -3 mm/s (Quasistatic) to 2.66 ×10 3 mm/s. The results show that the fracture energy and the flexural strength increase as the loading rate increases for these three concretes. Besides, such a trend is relatively mild under low rates. The gain of the flexural strength is around 30% compared with its quasi-static values. For Concretes PA and PB, the enhancement of fracture energy is around 20%, but 30% for Concrete PC. However, under high rates the increase in the fracture energy and the peak load are pronounced. For Concrete PA, the dynamic increase factors of the flexural strength and the fracture energy are approximately 6 and 3, while for Concrete PC, they are around 4 and 2 respectively. That is, the higher the fiber content is, the less rate sensitivity gets.