Physicochemical, mechanical and thermal analysis of unfired clay bricks: Kaolinite-PEG 6000 composite

Abstract

This study aims to evaluate the potential of polyethylene glycol (PEG 6000), a recycled material, as an additive to improve unfired clay bricks. By proposing a sustainable alternative to traditional methods potentially linked to medical waste. This research explores the physicochemical, mechanical and thermal properties of unfired clay bricks modified by different contents of PEG 6000 (0%, 1%, 3%, 7%, 15% and 20% by weight) according to the standard NM 13.1 0.0442005. The testing methods comply with recognized building sector standards (Belgian NBN EN 771-3+A1 and American ASTM C675-17). The clay used was extracted from Berrechid city and it is identified as kaolinite and some trace of illite, which has non-swelling properties. The incorporation of PEG 6000 into the unfired clay bricks has notably reduced the porosity rate from 3.91 % to 1.21 %, an improvement of 69 % compared to the reference sample, leading to a decrease in the rate of capillary water absorption. The bulk density of the bricks has slightly decreased to 1670.07 kg/m³, which still allowed them to be classified as light bricks. The incorporation of 7% of PEG 6000 increased compressive strength and flexural strength up to 15.98 MPa and 0.959 KN respectively, an improvement of 63.23 % compared to the reference sample, making them suitable for the construction of interior and exterior walls according to the standard NBN EN 771-3+A1. However, thermal conductivity and specific heat capacity have been improved by 42.22 % compared to the reference sample, reaching 0.26 W/m.K and 0.89 kJ/kg.K respectively. Optimization showed that 7% of PEG 6000 is the optimal percentage for manufacturing high-performance bricks, taking into account all properties studied previously. Moreover, the simulations carried out by the TRANSYS software suggest significant energy gains in terms of insulation, achieving up to 58.33% energy savings. In essence, this research demonstrates the potential of PEG 6000 as a sustainable additive for unfired clay bricks, offering improved properties and promising energy efficiency benefits.