Behavior of Semi Lightweight Reinforced Concrete Beams Under the Influence of Flexural Loads

Abstract

The presented study involves an experimental investigation into the influence of semilightweight concrete on the structural response of reinforced concrete beams. In this research, six beam specimens with specific dimensions of 100x200x1800 mm were subjected to testing. The research involves the creation of lightweight concrete, achieved by replacing a portion of the conventional fine and coarse aggregates in the concrete mixture with polystyrene foam granules. To enhance the concrete's strength, properties, and workability, a superplasticizer and silica fume additives were incorporated. The experimental program made trial mixtures with different proportions of replacing a mixture of aggregates with polystyrene foam granules, and then lightweight concrete was obtained with a strength of 22.5Mpa and density of 1750 kg per cubic meter by replacing 40% of the mixed aggregate by weight with polystyrene foam granules by volume. Then, six semi-lightweight concrete beams were cast with different reinforcing models. The beams were studied and examined during casting, treatment, and testing in terms of bending, flexural, and strain of the lower reinforcing steel and compression zone concrete, determining the deflection, modulus of elasticity, effective moment of inertia, crack pattern, and knowledge of Type of failure for each beam to compare it with the different codes for designing concrete structures. Through this study, it was found that The values of failure moments for lightweight reinforced concrete (LWRC) obtained from test results are lower than theoretical calculations of moments for normal concrete (fcu = 22.5 MPa) by a rate ranging between 10 to 25 %, according to the percentage mentioned by the American code. The values of failure moments for lightweight reinforced concrete obtained from test results are lower than theoretical calculations of moments for normal concrete (fcu = 40.0 MPa) by a rate ranging from 20 to 35%. From the compression test of the cylinders, it was found that the modulus of elasticity of semi-lightweight concrete using polystyrene foam granules was less than the Egyptian Code calculations for the modulus of elasticity of ordinary concrete by 10%. Still, it was 10% higher than the American Code calculations.