Assessment of hook end steel fibre as a substitute material in high performance concrete beam

A study was done to identify the optimum fibre content to achieve the maximum flexural capacity of high performance concrete beam. Hook end steel fibre of diameter 0.75 mm and 60 mm length has been used. The proportion of steel fibre is 0%, 1%, 2% and 3% by mass, and this is done by adding to concrete mixture. The targeted compressive strength of concrete is more than 70 MPa since it is high performance concrete. From the flow test, as the steel fibre content increases, the flow started to decrease. The flow result for 0%, 1%, 2% and 3% steel fibre are 654 mm, 605 mm, 584 mm and 556 mm respectively. The superplasticiser dose should be increased as steel fibre content increase to maintain the same flow. From compressive strength test, the addition of steel fibre increases the compressive strength of high performance concrete. The optimum steel fibre of 2% able to achieve maximum compressive strength of 105.7 MPa (14.9% gain in compressive strength than control sample). Other than that, addition of steel fibre also improves the tensile strength of concrete. The optimum steel fibre of 2% able to achieve maximum tensile strength of 9.1 MPa (46.8% gain in tensile splitting strength than control sample). Four beams were cast of size 100 mm x 300 mm x 2000 mm for the four-point flexural test. The highest flexural strength that was obtained is 21.65 MPa which was achieved at 2% of steel fibre. Further increase of steel fibre more than 2% reduced the respective strength of high performance concrete.