RESIDUAL PROPERTIES OF BASALT AND POLYPROPYLENE HYBRID FIBRE REINFORCED CONCRETE EXPOSED TO ELEVATED TEMPERATURES

摘要

One of the important issues about concrete of-late is its behaviour during fire. The mechanical properties of concrete decrease on exposure to a temperature above 300℃. In order to circumvent this problem, hybridization of two or more types of fibres in concrete is gaining importance. A high modulus fibre helps in preventing thermal cracks, whereas low modulus fibre (polypropylene, nylon) helps in preventing spalling by reducing pore pressure. An experimental study was conducted to explore the use of basalt fibres. The aim of this study was to develop a concrete that shall be able to retain strength and prevent spalling even after exposure to 800℃. It has been found that hybrid fibre reinforced concrete with polypropylene (V_f = 0.25%)+basalt (V_f=0.50%) fibres retained upto 70% strength when exposed to elevated temperature of 800℃, whereas control specimens retained only 52% of their original strength. In addition, no spalling was observed for both basalt fibre reinforced concrete (BFRC) and hybrid fibre reinforced concrete (HyFRC) even when exposed to 1000℃ temperature for all mixes. A relationship between residual properties and fibre dosage was developed to optimize fibre dosage for a temperature range of 25℃ < t < 1000℃.