EFFECT OF PLATEN RESTRAINT ON STRESS-STRAIN BEHAVIOUR OF CONCRETE UNDER UNIAXIAL COMPRESSION

Abstract

The results of an experimental investigation of platen restraint on the behaviour of concrete in uniaxial compression are discussed. The effect of four anti-friction media viz. Neoprene, PVC, Teflon and Grease on platen restraint was studied for a normal strength concrete (Nominal 28- day cylinder strength of 25 MPa) and a relatively high-strength concrete (Nominal 28-day cylinder strength of 50 MPa ). The testing of the cylindrical specimens under a strain rate of 2.25 mm/hour indicate that the ascending branch was insensitive to platen restraint and the anti-friction media had no role to play. In the case of normal-strength concrete, the descending branch was significantly affected by platen-restraint and an almost brittle failure marked by a vertical descending branch was obtained with grease as the anti-friction media, which was also most effective amongst all the anti-friction media under investigation. The anti-friction media had a relatively smaller role to play in the case of relatively high strength concrete where the descending branches had a sharper slope compared to the normal- strength concrete. Even for the relatively high-strength concrete, grease was relatively the most effective anti-friction media. Thus investigation indicates that unlike the ascending branch, the descending branch is not a intrinsic material property of concrete.