MECHANICAL BEHAVIOUR OF SIMPLE SUPPORTED TWO LAYERS REINFORCED CONCRETE (LWC-NSC) BEAM

This paper represent an experimental investigation of the layered beam to study the possibility of Utilizing the weak effect of the concrete at the tension zone of a loaded simply supported concrete beam that lay at this zone practically by using a lightweight concrete as a part of this region to produce a beam with lighter weight that homogenous RC beam. Where a rectangular beams section (150*200*1000)mm cast with Light-weight concrete (produce by replacing the coarse aggregate of the main normal concrete mix by a crash limestone once and another by replacing 50% of normal coarse aggregate with chopped chopped rubber tyre) in tension zone and normal strength concrete at the rest part and compare it with H RC beams. three deferent level of the lightweight layers (1/3,1/2 and 2/3 of the beam thickness) were studied, all beams tested under Two point load till failure. The result of the maximum load capacity show that there was a clear lowering in load capacity of the beam, but as the lightweight layer increase as this lowering in the load capacity became less, where for (1/3,1/2 and 2/3) replaced thickness the lowering percentage compare with the HRC beam are (-18.96%,- 8.39% and -7.70%) for the mix with crushed limestone and the lowering in weight are (-6.27%, -9% and - 12.59%) for the same sequence respectively