Engineering properties of polystyrene aggregate concrete
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The project reported in this thesis was concerned with the ultilization of re-cycled polystyrene granulates as lightweight aggregate for use in concrete. A manufacturing process for the conversion of polystyrene waste from the packaging industry into chemically coated expanded polystyrene aggregate was developed by Building Systems Technology (BST) Pty. Ltd. When the treated polystyrene aggregates are incorporated into fresh mortar or concrete they are uniformly and evenly distributed in the cement paste or the mortar matrix. The polystyrene aggregate produced by BST was used to establish the workability, strength, deformation, bond strength, and the functional properties of the concrete. The properties of the concretes made with the polystyrene aggregate were compared with concretes made with normal weight aggregates of equivalent mix proportions using General Purpose Portland (Type GP) cement. It was found that it is generally feasible to manufacture structural grade lightweight concrete from treated re-cycled polystyrene aggregate. No reduction was observed in the compressive and tensile strengths, and the modulus of elasticity of concretes made with the polystyrene aggregate, and cured in water over a period of about one year. The maximum cylinder compressive strength of concrete made with the treated polystyrene aggregate satisfied the strength requirement of medium strength structural reinforced concrete. This investigation has shown that structural grade polystyrene aggregate concrete having saturated surface-dry density of 1800 kg/m³ to 2400 kg/m³ can be produced with cylinder compressive strength up to 32 MPa. The test results have shown that, for a stress/strength ratio of 30% of the 28-day cylinder compressive strength, the creep strain of polystyrene aggregate concrete compares well with concrete made with normal weight aggregates. The functional properties such as impact resistance and freezing and thawing durability of concrete is improved when polystyrene aggregate is incorporated. From the conclusions derived, design recommendations are suggested. Limitations of the investigation and suggestions for future work are presented.
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