RESIDUAL BEHAVIOUR OF CONFINED FIBER REINFORCED HIGH STRENGTH CONCRETE EXPOSED TO ELEVATED TEMPERATURES

Abstract

The use of High Strength Concrete (HSC) is very popular in columns of high rise buildings and special structures like nuclear reactors, chimneys, and cement plants because of its more durability, high concrete compressive strength, and low permeability than normal strength concrete. As those structures are exposed to high temperatures there is a need to investigate the behavior of HSC at high temperatures. Over the year, limited research has been done on the behavior of confined fiber reinforced high strength concrete exposed to elevated temperature. The aim of the present study is to investigate the residual behavior of confined polypropylene fiber reinforced HSC after exposure to high temperature and the parameters studied are transverse reinforcement, effect of addition of fibers and concrete compressive strength. The experimental investigation consisted of casting one hundred cylindrical specimens of size 100 x 200 mm with plain and confined polypropylene reinforced HSC. The transverse reinforcement was provided in the form of hoops at varying pitches. The polypropylene fibers were added to the concrete mix with various volume fractions. All specimens were heated to different temperatures ranging from room temperature to 800° C and tested under axial compression. The results showed that, polypropylene fibers are more effective when concrete is exposed to high temperature and the effect of confinement was less pronounced for higher grade of concrete than lower grade concrete at all temperatures. The results also show that up to 200 C, there is not much variation in strength and strain. However strength is decreased and strain is increased as temperature is increased beyond 200 C with the available experimental data, statistical analysis has been done and an equation was proposed to calculate strength and strain at peak and post peak.