FRACTURE MECHANICS OF FIBRE CONCRETE

Abstract

Fiber reinforced concrete is particularly suitable for use where tensile strength or impact resistance is required. Since the fracture mechanics is a I new method to study the behavior of materials, no exact and available data about fracture mechanics in fiber reinforced concrete is available. The work presented in this thesis was conducted to study fracture mechanics of fiber reinforced concrete, specially the energy release factor (GF), and the stress intensity factor (Kic). I

In order to study the previous factors of fracture mechanics, six groups of different fiber reinforced concretes with a total number of forty four mixes I were prepared and tested. Mix proportioning of different mixes was based on a lot of trial mixes The variables of this study include fiber type and content, I concrete grade, initial crack length to depth ratio, beam width to depth ratio, and crack tip shape. Load-deflection and crack opening distance were I determined. The results were analytically examined and verified. The energy release factor (GF) was determined according to the recommendations of RILEM Technical-Committee 50-FMC. Whereas, the stress intensity factor (K1c) was determined and verified using the guidelines of ASTM-E399 and the model proposed in Zagazig University, Egypt. I

The test results showed that, when concrete compressive strength increased, its brittleness increased as well. Accordingly, the fracture energy I characteristics became worse as the concrete strength increased. Steel fiber showed better fracture resisting behaviour compared to the other two types I (glass and polypropylene fibers). This may be due to the higher bond strength of crimped steel fibers.