In this study, PET plastic waste, which is a type of polymer commonly used in the manufacture of plastic bottles, has been incorporated into concrete by partially replacing the natural fine aggregate. An experimental study was conducted by casting and testing 90 concrete cylinders and 54 concrete cubes. A concrete mixture was designed in which the natural fine aggregate was substituted partially with PET plastic waste (PW) at a ratio of 0%, 25%, and 50%, with various w/c ratios of .40, .45, and .55. Physical, mechanical, and durability properties were assessed. The downside of the test results show degradation in each of the following characteristics: slump, compressive strength, splitting tensile strength, ultrasonic pulse velocity, water absorption, and porosity. The degradation of these characteristics increased with the increase in the volume of plastic aggregate (PA) and the w/c ratio. While the positive side of the results showed that with the increase of the PA volume and the w/c ratio, the fresh and dry densities decreased further, and by using 50% PET, the dry density became below 2000 kg/m³. Therefore, it is classified as lightweight concrete. Moreover, the fracture of concrete changed from brittle to more ductile compared to control concrete. Also, the thermal conductivity decreased significantly (11%–47%), and by using 50% of PET, the thermal conductivity became less than .71 W/mK, and accordingly, classified as a bearing insulator.

Existence of ultra-high performance concrete (UHPC) is the result of one of the latest advances in concrete technology. As compared to the normal concrete mixtures, the mixtures of UHPC are reported to have several times more strength, elastic modulus, fracture toughness, ductility and durability. UHPC is prepared by mixing high amounts of cement and silica fume with fine quartz sand, quartz powder and fibres. The water to binder ratio is kept very low and therefore a high dosage of superplasticizer is needed to maintain the required flowability. Need for a fine quartz sand and quartz powder for producing UHPC mixtures increases the cost of UHPC in places where these ingredients are not naturally available. In the present study, an attempt was made to develop an optimum mixture of UHPC using readily available local fine dune sand. The local dune sand was used collectively as a natural mixture replacing fine quartz sand and quartz powder. To select an optimum UHPC mixture, several trial mixtures were considered by varying the proportions of the ingredients of UHPC. An optimum mixture of UHPC was selected based on optimum flow (above 180 mm), strength (above 150 MPa) and lower amounts of silica fume and steel fibres to reduce the unit cost. A series of tests were conducted on the specimens prepared with the optimally selected mixture of UHPC for determining its mechanical properties and durability characteristics including resistance against reinforcement corrosion and sulphate attack. Test results indicate an excellent performance of the optimum mixture of UHPC developed through the present work.