ABSTRACT
This experimental investigation was carried out to determine the strength of concrete confined by plastic pipe and the effect of slenderness ratio on the strength. Pipes of 75mm and 100mm diameters of varied lengths: 410mm to 1210mm were used. Two different concrete mixes were tested: a 1.5 sand-cement ratio and 3 coase aggregate cement ratio. The second had a 1.0 sand - cement ratio , and 2.0 coarse aggregate cement ratio. The samples were made into three series and one group was reinforced with 6mm diameter bars. All tests were carried out in uniaxial compression under monotonic loading. Results showed appreciable increase in concrete strength when confined by the plastic pipe. Increase in strength of about 2 times the strength of unconfined concrete was recorded. The reinforcement bars were of no significance in terms of strength increase particularly in the case of short columns. By slender columns slight increases were recorded.