EXPERIMENTAL STUDY ON REINFORCED CONCRETE BEAMS WITH HYBRID STEEL- POLYPROPYLENE FIBERS

Abstract

This study discusses the results of experimental tests on reinforced concrete beams containing hybrid fibers consisting of different ratios of steel fiber (SF) and polypropylene fibers (PPF). Steel fibers crimped type 50 mm in length and 1 mm in diameter were used as reinforcement in volume fractions of 0.5%, 1%, and 1.5%. Polypropylene fibers with a length of 12 mm were used in volumetric fractions of 0.15% and 0.3%. In the present study, cubes of (150 x 150 x 150 mm) and reinforced concrete beams (120 x 200 x 1200 mm) were casted for compressive strength test and a flexural loading test on beams, respectively. Seven beams, including a specimen of a control beam, had been casted. The experimental results indicated that the increase in the mixture's fiber content increases the loss of workability. All concrete mixtures showed improvement in compressive strength test results due to the improvement of the hybrid fibers on the final resistance properties. As a result of the influence of the hybrid fibers on beams, the number of cracks has increased and distributed more effectively, indicating an increase in the ductility of the concrete and thus improves the structural performance of the beams. The load- carrying capacity was found to increase with the addition of the fibers for all beams. The highest ultimate load was obtained when adding 1% steel fibers and 0.15% polypropylene. The evaluation of the load-deflection curves of the hybrid mixtures showed that the fibers contribute significantly to maintaining the structural integrity and stability of the concrete and thus contribute to extending the service life of the building.