One-Year Push-Off specimens using cocktail and polymeric fibres at elevated temperatures

Shear failure is generally considered to be among most of the critical topics in reinforced concrete structures due to specific features that shear failure possesses, including no warning signs and brittle nature, especially after exposed to elevated temperature. The push-off model is adopted to investigate the shear performance at the current study using different types of fibres. Two mixes have been tested herein, i.e., one mix contains 4 kg/m3 of polymeric fibres whereas the other mix contains cocktail fibres, i.e., 2 kg/m3 of polymeric fibres and 40 kg/m3 of steel fibres simultaneously. Test setup is designed to measure the deformations occurred at the shear surface plane using means of Linear Variable Differential Transformers (LVDTs), fixed horizontally and vertically on both faces of the specimen. Thus, two different deformations are investigated: vertical displacement considered as “crack slip” and horizontal displacement considered as “crack width”. Each concrete mix is investigated by exposing the related specimens to one of the five different maximum temperatures adopted. Results showed that, at ambient temperature, shear capacity is significantly increased by the virtue of using cocktail fibres, while insignificant increase is noticed using polymetric fibres only. However, significant decrease is noticed when elevated temperatures are included for both mixes.