Effects of steel fibres on concrete properties and flexural behaviour of reinforced concrete slabs

Abstract

Concrete is a material that is good in compression but weak in tension. Enhancing the tensile properties of concrete will lead to its greater application in construction. It was reported that improvement on the mechanical properties of reinforced concrete structure can be achieved by the inclusion of short fibres. The use of short steel fibres have been reported to increase the toughness, abrasion, impact resistances and allow for decrease in concrete slab thickness. This paper focuses on the study conducted in the laboratory on the effect of steel fibre on concrete properties and behaviour of steel fibre reinforced concrete slabs under flexure with different amount of tensile reinforcements. A number of concrete cubes and prisms with and without steel fibres, 0%, 0.5%, 1.0%, 1.5% and 2.0% together with four reinforced concrete slabs having different amount of tensile reinforcement were cast and tested to failure in flexure. The optimum dosage of steel fibre to be included in concrete slab was 1%. The reinforced concrete slabs manufactured consist of slab with tensile reinforcement bar of R-150 as control slab, slab with tensile reinforcement bar of R-300 and 1% dosage of steel fibres, slab with 1% dosage of steel fibres without tensile reinforcement, and one plain concrete slab without reinforcement. All the slabs cast having the overall dimensions of 100 x 500 x 1000 mm, and tested to failure under four point loading. Cube compressive strength, modified compressive strength, flexural strength, ultrasonic pulse velocity test and rebound hammer test were conducted. The behaviour of the reinforced concrete slabs was studied through their ultimate load, load-deflection characteristic upon loading, cracking history, and mode of failure. The experimental results show that the inclusion of steel fibres was found to improve the compressive strength, slightly lowered the UPV value but no significant effect on the rebound hammer compared to the control sample. It was also found that based on slab SB-R300-1SF the inclusion of steel fibres increased the ultimate load of the slab by 25%, reduce the tensile reinforcement by about 50%, improve the flexural stiffness and ductility of the slab when compared to the control slab, SC-R150.