FLEXURAL BEHAVIOR AND SIZE EFFECT OF FULL SCALE REINFORCED LIGHTWEIGHT CONCRETE BEAM

Abstract

This article presents the results of experimental investigations on the size effect and the flexural behavior of full size reinforced concrete beams with lightweight aggregate and normal aggregate. The lightweight aggregate (LWA) was manufactured with fine sediments collected from the Shih-Men Reservoir in Taiwan. A total of 6 flexure beams with various reinforcement ratios (from 0.33% to 1.3%) and 6 size-effect beams with various dimensions were fabricated and tested. The designed compressive strength of concrete was 34 MPa. Test results indicated that the reinforced lightweight aggregate concrete (LWAC) beams had a similar load capacity and failure mode as those of normal weight concrete (NWC) beams, but demonstrated larger ultimate deflections and curvature ductility. The curvature ductility of both types of concrete beam decreased as the reinforcement ratio increased. On the other hand, an increase of the beam dimension lead to increases of the load and deflection at the yielding strength and ultimate strength, but reduced the ultimate deflection ratio for both types of concrete beams. In addition, the ultimate deflection-to-span ratio varied from 1/115 to 1/150 (23% reduction) as the effective depth increased from 300 mm to 600 mm for the NWC beams and from 1/84 to 1/188 (55% reduction) for the LWAC beams, respectively. This reveals that the decay of ultimate deflection ratio of the LWAC beams due to the increase of beam size is more significant than that of the NWC beams.