Development of sustainable concrete using recycled high-density polyethylene and crumb tires: Mechanical and thermal properties

Recycling the non-biodegradable waste materials in concrete is becoming necessary to reduce the environmental pollution in industrial and urbanization countries. Further, since energy-saving is a critical issue worldwide, particularly in hot climate conditions, minimizing the heat flow from the outside to inside the building roofs is also the demand of both the residents and authorities as reflected by the building's codes. In this regard, experimental work was conducted to investigate the concrete's mechanical and thermal properties. Two replacement materials, namely crumb rubber (Ru) and high-density polyethylene (HDPE), were used to replace fine and coarse aggregates to produce insulation concrete. Further, the cost analysis, oil fuel consumption, CO2, and SO2 emissions were computed as a function of the thermal resistance that was figured out from experimental work. The experimental results of insulation concrete revealed that the thermal conductivity was reduced by about 40%, with little lower values for rubber as related to polyethylene. Likewise, it was found that the use of Ru and HDPE with a maximum dosage of 50% resulted in reducing the strength of normal concrete with a maximum value of 90% and 82% for Ru and HDPE, respectively. The flexural strength decreased with increasing Ru and HDPE's content by about 50%. In contrast, the use of Ru and HDPE in the concrete enhanced the ductility performance. Results suggest the usage of screed concrete with 50% of Ru and HDPE replacements to achieve maximum thermal resistance. It is found that the best mixtures (Ru-50% and HDPE-50%) enhance the thermal resistance by about 59 and 48% as compared to the control normal concrete mixture. Based on net present value (NPV) over 30 years, the thermal resistance improvement could decrease the cost of energy consumption from 596 to 377.2 and 405.1 $/m2 for concrete with Ru-50% and concrete with HDPE-50%, respectively. Furthermore, these two optimal mixes could also minimize the oil fuel consumption, CO2 and SO2 emissions from 75.14, 243 and 1.26 (kg/m2.year) to 47.34, 152 and 0.79 (kg/m2.year) when Ru-50% of coarse replacement is used and 50.92, 164 and 0.85 (kg/m2.year) when using HDPE-50% with coarse aggregate replacement, respectively.