STUDY OF PLASTIC FIBRE CONCRETE MANHOLE COVERS

Abstract

The work relates principally to the behaviour of Medium -duty R.C. Manhole Covers made with plastic fibre concrete under static and impact loading. The fibre used it polypropylene fibre. Deflections and crack widths have been measured at various stages of loading upto failure. The influence of fibre addition on compressive and flexural strength of concrete has also been studied. The experimental programme included tests for compressive strength and flexural strength of concrete with fibre contents varying from 0-2 Y. Forty Medium - duty R.C. Manhole Covers were cast by vibro-pressing with fibre contents varying from 0-2 6/.. The covers were 600 mm dia x 77 mm thick, and were provided with 4.2 mm thick steel flat edging to which the rein-forcing bars were welded. Twenty covers were tested under mono-tonic loading upto failure, and central deflection and crack widths were measured. The remaining covers were tested under impact by dropping a 0.5 kN weight through a height of 0.5 m at the centre of the cover. The blows were applied repeatedly till the cover failed due to spalling of concrete on tension face. Crack widths were measured at different stages of loading upto failure. The test results show that with addition of fibres, the ultimate strength and impact resistance of the cover is improved and the failure is more ductile. The increase is observed to be maximum when fibre content is 1 Y. by volume. Under static loading the increase in ultimate load with 1 ic fibre content is 22 y:. Under impact loading the impact resistance is found to increase by eight times when fibre content is 1 I. by volume.