Effect of polypropylene fiber on the strength properties of structural lightweight concrete with different unit weights

Structural Lightweight Concrete (SLWC) is a commonly used type of concrete in the civil engineering field due to its significant properties such as: better thermal fire resistance and lower unit weight compared with conventional concrete. In this study, pumice stone as a type of lightweight aggregate is used in different sizes from 0.5 to 2 mm to produce three different unit weights of lightweight concrete (G1, G2, and G3) with various percentages of polypropylene fiber volume (0.0 %, 0.25%,0.50%). This study investigated the effect of unit weight and polypropylene fiber on the fresh properties of lightweight concrete such as workability. The effects on the mechanical properties of lightweight concrete were also studied such as compressive strengths, flexural strengths, split tensile strength, thermal conductivity and evaluated temperatures (200, 400, 600 and 800oC). With the reduction of the unit weight of lightweight concrete an increase in workability is observed while the higher the volume of pp fiber the workability increases. With an increase in the volume of polypropylene fiber from 0% to 0.5% and a decrease in the unit weight of lightweight concrete the compressive strength and the split tensile strength decreases. However, the flexural strength, thermal conductivity and evaluated temperatures (200, 400, 600 and 800oC) are all improved. When the percentage of polypropylene fiber is increased from 0.0% to 0.50% the optimum vale of flexural strength is obtained and found to be 2.5 MPa. Without the addition of pp fiber, the maximum values of compressive strength and split tensile strength are obtained to be 30 MPa and 2.11 MPa respectively.