Thermal insulation of mud bricks made with walnut shells: Characterization and simulation study

Abstract

This work aims to study the thermal performance of a new bio-composite (clay-walnut shell). Firstly, a geotechnical analysis was carried out on the soil. Different percentage additions: 0, 10, and 20% by weight (wt.%) of walnut shells were adopted to evaluate the thermal impact of WS on unfired clay bricks. Then, the thermophysical properties of produced bio-composites were compared with those of clay alone. The thermal transport properties were measured using the hot disk method. Geotechnical analysis showed that the base material (soil extracted from Nador city; eastern Morocco) has a high clay fraction of 51.8 % and moderate plasticity. Thermal analysis showed that WS improves the thermal insulation of mud bricks while reducing the density. Introducing 20 wt% WS decreased the thermal conductivity of clay by 45.22%, resulting in an increase in thermal resistance. Finally, a comparative study on the dynamic thermal behavior of two types of walls (concrete block wall and clay brick wall − 20 % by weight of walnut shells).The numerical findings revealed that the use of the developed composites increased the energy performance of residential buildings allowing respective savings (10.8% − 7.94%) of energy for heating and cooling needs, motivating the proposal to use WS as a new aggregate for construction.