Investigation of waste EPS foams modified by heat treatment method as concrete aggregate

Abstract

The method for the recycling of expanded polystyrene foam (EPS) in waste state, which causes a significant environmental pollution, is presented in this study. With this method, modified EPS aggregate was produced by heat treatment applied on 10 × 10 × 10 mm EPS aggregates and the production of a new type of lightweight concrete was aimed by means of being used instead of sand. This disadvantage of EPS aggregate concretes with low compressive strength values has been turned into an advantage through heat treatment method. In this method, the heat treatment process temperatures were determined as 75 °C, 100 °C and 125 °C, while the durations of processes were determined to be 15, 30, 45 and 60 min. The ideal heat treatment temperature and time is determined to be 15 min at 125 °C. 16 samples with various aggregate rates were produced, and the following results were obtained from the tests carried out: i) During 15 min of heat treatment at 125 °C, while the volume change decreased by 12 times, the unit weight increased by 21 times and turning into the form of a synthetic lightweight aggregate. ii) Modified EPS aggregated concretes can be used in building parts where semi-carrier lightweight concrete is required with its strength (with values of 12.66–15.83 MPa up to 40% volumetric ratio. iii) Thermal conductivity coefficients of new concretes vary between 0.154 and 0.481 W/mK. It is conferred that modified EPS aggregate concretes can be used both for insulation purposes and as semi-carrier lightweight concrete.