FLEXURAL BEHAVIOR OF HIGH STRENGTH REINFORCED CONCRETE BEAMS STRENGTHENED BY HYBRID FIBERS

An experimental program is achieved to study the enhancement gained from adding different volumetric ratios of hybrid steel, basalt, and glass fibers to high strength concrete mixes, and to investigate the flexural behavior of rectangular reinforced concrete beams produced from these fibrous mixes. Ten rectangular beams, which are identical in geometry and reinforcement, are tested. The first one is a control beam, group A consist of three beams strengthened by different ratios of steel fibers only, group B consist of three beams strengthened by different ratios of hybrid steel-basalt fibers, and group C consist of three beams strengthened by different ratios of hybrid steel-glass fibers. Results and comparative studies expressed in the form of graphs and tables show variable enhancement values in crack, yield, and ultimate loads capacities for the tested beams. Standard high strength concrete cubes and cylinders test results indicate that compressive strength for all the fibrous mixes is slightly worsened, especially for hybrid steel-basalt fibers, due to the increase in matrix porosity whereas the splitting tensile strength is enhanced. Generally, yield and ultimate load capacities for most of the fibrous beams are reduced, especially for hybrid steel-basalt fibrous beams due to the smooth texture of basalt fibers. In addition, adding glass fibers hybridly with steel fibers enhances crack formation and propagation without a noticeable reduction in yield and ultimate load capacities.