Enhancing Concrete Strength and Thermal Insulation Using Thermoset Plastic Waste

Abstract

Structural concrete is the most frequently used construction material in the world because of its known advantageous characteristics. However, concrete has some limitations, such as its low tensile strength, low strength-to-weight ratio and moderate thermal insulation. Improving these characteristics was the aim of a laboratory-based investigation into the behavior of concrete made in the presence of ground melamine-formaldehyde (MF) thermosetting plastic waste as a sand replacement. The MF is a cross-linked thermoset polymer that cannot be recycled or reprocessed, presenting a serious solid waste disposal problem. The laboratory-based program included tests of tensile and compressive strengths, unit weight and thermal insulation characteristics. The tests were carried out on concrete and mortar with various water-to-cement (w/c) ratios, and sand was replaced by MF at different percentages that ranged from 0% to 60%. The results indicated that replacing sand with MF resulted in a lighter-weight concrete with improved characteristics. In general the strengths were increased as the percentage of MF was increased to reach maximum values at approximately 30% MF. In comparison with control specimens without MF, the strength/weight ratio of concrete was increased by up to 47% and the tensile strength of mortar was increased up to 16%. With regards to thermal insulation, a drop in temperature up to 30% was recorded in specimens with 60% MF. In conclusion, this investigation showed that the addition and reuse of MF in concrete mixes significantly improved the mechanical and thermal characteristics of concrete. This would be an effective approach when added to other protection methods of solid waste, as it addresses the specific waste of MF.