FLEXURAL BEHAVIOR OF HYBRID REINFORCED CONCRETE BEAMS COMBINING ULTRA HIGH STRENGTH CONCRETE AND PORECILENITE AGGREGATE LIGHTWEIGHT CONCRETE

The main objective of this research was studied the flexure behavior of hybrid reinforced concrete beams combining reactive powder concrete (RPC) and lightweight concrete (LWC). The experimental work consists of casting and testing in flexure seven simply supported reinforced concrete beams. The dimensions of (7) beams were geometrically similar, having rectangular cross-section, of dimensions (125×200×1600) mm. Lightweight concrete was used in tension layer and reactive powder concrete was used in compression layer for all hybrid concrete beams. The main variables were; type of concrete (LWC and RPC), thicknesses of RPC layer (hR =0, 50, 100 and 200) mm and longitudinal reinforcement ratios (ρ= 0.0033 and 0.0227). The type of LWC used in the experimental work was porecilenite aggregate. The results showed that the characteristic strength (first and ultimate loads) was increased when the thickness of RPC layer was increased. In addition to that, these parameters were decreased the values of deflection. All beams failed by flexure mode without any shear cracks which achieved by yielding of tensile steel in the tension zone. Also, for all hybrid beams, the slip was absent between the concrete layers. Finally, the reinforcement ratio (ρ) had more effective factor of all parameter used to increase the stiffness value of the beams which increased the characteristic strength and reduced the deflection values.