Synthetic fibres or fibre cocktail in terms of shear capacity of concrete after elevated temperatures

Abstract

Elevated temperatures can substantially affect the shear capacity of concrete. Herein we examine the effect of using different types of fibres on the behaviour of concrete at different maximum temperatures in terms of shear failure. The experiments were carried out by testing thirty specimens using two types of fibres at the age of 28 days. The study has adopted the push-off model for testing, which has been widely used as a relatively small, inexpensive, easy to perform and no need for special equipment, using either synthetic fibres or fibre cocktail. In addition, both crack width and crack slip have been investigated using LVDTs in both directions. The shear tests have been carried out at cold state after exposure to different levels of elevated temperatures. Using a bi-component synthetic fibre with 4 kg/m³ approved to enhance the concrete ductility and toughness. However, using cocktail fibres, containing both synthetic fibres of 2 kg/m³ and steel fibres of 40 kg/m³, showed higher values than using synthetic fibres in terms of shear. Finally, mixes containing fibre cocktail showed more ductile behaviour than mixes with synthetic fibres at low as well as high temperatures.