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.
