EFFECTS OF COARSE AGGREGATE SIZES WITH GLASS FIBER ON SHEAR BEHAVIOR OF REINFORCED CONCRETE BEAM

Abstract

In the current day construction industry in Ethiopia, concrete has emerged as the most common building material. Hence careful consideration must be given to factors that affect its strength. One of the factors affecting the shear strength of concrete is the size of coarse aggregate used in the mix of concrete. This thesis carried out by using 1:1.52:2.28 cement, sand and coarse aggregate mix ratio, 0.55 water-cement ratio, 10mm, 14mm, 20mm and 37.5mm coarse aggregate sizes for experimental shear strength test in the laboratory by using three point load universal testing machine at 28 days. The study investigated fourteen sets of concrete samples for each had three replication; seven sample with 0.25% glass fiber and the rest seven without glass fiber all concrete sample made using the cement treated aggregate gradation procedure. The result showed that by Appling 61.6 KN up to 108 KN external load deflect the beam without glass fiber but a beam with glass fiber needs 73.1 KN up to 127.1 KN this result shows with glass fiber increased 8.07% up to 15.73%; The bending moment of the beam without glass fiber 6943.74 Nm up to 12163.74 Nm but with glass fiber 8237.49 Nm up to 14312.49 Nm this result shows with glass fiber increased 7.5% up to 15.7%; The shear force without glass fiber varies from 30922.13 N up to 54122.13 N but with glass fiber 36672.13 N up to 63672.13 N this result shows with glass fiber increased 7.5% up to 14.99 % and Shear strength without glass fiber varied from 11.61 MPa up to 20.29 MPa but with glass fiber 13.81 MPa up to 23.93 MPa this result shows with glass fiber increased from 7.78% up to 15.91%. It was concluded that shear strength of concrete made from uniform size aggregates increases with decrease in aggregate size and that well graded aggregates using the cement treated aggregate gradation procedure resulted in concrete of lower shear strength relative to those produced using uniform size aggregates such as 10mm and 20mm. It was also conclude that concrete made from combined aggregates have less shear strength relative to concrete made from uniform size aggregates and well graded aggregate.