Experimental Study to Measure Conductive Heat Transfer Properties in New Materials with Environmental Waste Aggregates

Abstract

This study presents the design, development, and operational evaluation of the HD25 Hot Box, a guarded hot plate apparatus designed to measure the thermal conductivity of concrete specimens under steady-state conditions. The HD25 Hot Box was developed to assess the heat transfer properties of construction materials, particularly those incorporating environmental waste aggregates such as high- and low-density polyethylene and perlite. The device adheres to the Argentine standards IRAM 11559, IRAM 11549, and IRAM 11601, ensuring accurate and reliable measurements. The apparatus consists of two main units: a heating unit and a cooling unit, which work in tandem to establish a uniform, one-dimensional heat flow through prism-shaped concrete specimens. The HD25 Hot Box measures key thermal properties, including thermal conductivity, resistivity, resistance, and transmittance. The study highlights the impact of incorporating plastic waste into concrete, demonstrating that replacing traditional aggregates with plastic waste reduces the material´s density and thermal conductivity while increasing its thermal resistance and resistivity. For instance, replacing 37% of coarse aggregate with plastic resulted in a 40% reduction in thermal conductivity and a 68% increase in thermal resistance compared to conventional concrete. The device´s design includes a central heating plate surrounded by a guard section to ensure uniform heat distribution, and a cooling unit that uses a closed-loop water circulation system to maintain temperature stability. The HD25 Hot Box is compact, lightweight, and energy-efficient, making it suitable for laboratory use. The study concludes that the HD25 Hot Box is a reliable tool for evaluating the thermal properties of concrete, particularly those incorporating recycled materials, and provides valuable data for energy-efficient building design. The findings suggest that replacing up to 19% of traditional aggregates with plastic waste and perlite fines is optimal for maintaining both thermal and mechanical properties in construction materials.