Crack pattern investigation of hybrid fibre reinforced concrete under uniaxial tension

The effect of size and volume of fibres on the fracture of hybrid fibre reinforced concrete was determined by applying uniaxial tensile test. The bone shaped specimens were loaded under uniaxial tension by using freely rotated support loading test setup. The test results showed that the increase in fibre volume results in an increase in both tensile strength and the area under the load displacement curve, which is the measure of the material toughness. It was shown that the use of short fibres not only increased the peak load but also affected the post-peak behaviour and increased the toughness especially when they were used together with long fibres. The image analyses pointed out that in hybrid fibre reinforced concrete the crack patterns are not in general linear. Instead, the cracks propagate inside the samples forming multiple cracks and crack branches as well as developing bridging, though these features are not observed on the surface of the samples. The results showed that with increasing amount of short fibres the average crack area was increased, while the use of long fibres in more abundance increased the width of the largest crack. © 2020 Turkish Chamber of Civil Engineers. All rights reserved.