Recently, many types of research in Iraq have had the properties of lightweight concrete beams utilizing both artificial and normal aggregate for economic reasons. Very limited works have been implemented to investigate the resistance of flexural and shear behavior of structural lightweight aggregate concrete; therefore, it is important to study the properties and their structural behavior. The present work is to investigate the shear and flexural strength of lightweight concrete beams made of pumice with silica fume admixture. The lightweight concrete has been made by partial replacement of crushed gravel with 75% pumice and 7% silica fume. The value of compressive force strength is 29 MPa within twenty-eight days. A total of ten reinforced concrete beams is used, with dimensions of (150 x 150 x 750) mm, with and without silica fume, and with varying ratios of transverse reinforcement (stirrups). The deflection at mid-span was also measured using a mechanical dial gauge. Normal-weight concrete beams are also used for comparison with the lightweight concrete beams. Beam behavior was assessed in terms of ultimate deflection, failure mode, and crack pattern. According to the experimental results, the prepared concrete’s weight and strength met the LWC requirements. The results showed a significant effect of the transverse reinforcement ratio (stirrups), where the values of the shear and resistance of flexural rose when the amount of reinforcement increased. Furthermore, the appearance of the first crack has been significantly delayed as the reinforcement ratio rose.
