Effects Of Additives and The Volumetric Variation on Thermal Properties and Heat Transfer Characteristics of Clay Bricks

This study investigates the production of porous, lightweight clay bricks with improved thermal insulation and mechanical properties, targeting applications in energy-efficient construction. Utilising oat husk, an organic waste product, as an additive, this research aims to overcome the longstanding challenges associated with incorporating additives in energy-brick production. By employing an innovative pre-treatment process, both the mechanical strength and thermal conductivity of the fired clay bricks were enhanced, crucial for building applications.

In this study, raw materials, including oat husk in normal and ash-converted forms, were selected, pre-treated, and blended with clay at varying additive concentrations up to 30% by volume. The semi-dry mixtures were then mechanically compressed, dried, and fired over 12 hours, reaching a peak temperature of approximately 800°C. Both experimental and modelling approaches were employed to evaluate the thermophysical properties of the resulting samples, specifically thermal conductivity and compressive strength.

The results indicated that the addition of oat husk created porous, lightweight bricks with strong insulating qualities. Notably, the 30% additive sample achieved a thermal conductivity of approximately 0.41 W/mK, showing a reduction of over 31% compared to the control sample (0.60 W/mK), though with a decrease in compressive strength. An optimal balance was observed in samples with a 5% oat husk additive, which exhibited a compressive strength of 6.05 MPa, exceeding the control sample's 5.24 MPa by more than 15%, and retained a favourable thermal conductivity of approximately 0.566 W/mK.

These findings suggest that oat husk pre-treated with hydrochloric acid (HCl) can be effectively utilised to produce energy-efficient fired clay bricks with enhanced mechanical and thermal properties. This research contributes a viable solution for sustainable construction, addressing the challenge of organic additive incorporation in energy-brick production for building technology.