A Comparative Study of the Engineering Properties of Fired and Unfired Hollow Clay Bricks Stabilized with Lime and Pozzolana

Abstract

The transition to sustainable, energy-efficient masonry has renewed interest in stabilized earth-based bricks as alternatives to fired clay bricks. This study focused on a comparative study of engineering properties of fired and unfired hollow clay bricks stabilized with lime and pozzolana. A representative clay was characterized by particle size distribution, Atterberg limits, and X‑ray fluorescence (XRF). The soil was classified as a highly plastic, slightly silty sand, and both clay and pozzolana contained high reactive silica and alumina contents, indicating strong pozzolanic potential. Hollow bricks incorporating 0% to 8% weight of lime and pozzolana were produced and tested in fired and unfired conditions. Bulk density, water absorption, and 28‑day compressive strengths were determined. One hundred and fifty samples were prepared using the manual moulding method. These samples were tested for 7 ,14, 21 and 28days. Testing was conducted with a universal testing machine. Fired bricks were fired at a temperature of 900˚to 1100˚ in kilns and an infrared pyrometer thermometer for determining the temperature. Stabilized bricks, increasing lime and pozzolana content led to a higher density of 2071.98kg̷ m³ for stabilized 8%LP and 2089.30 kg̷ m³ for fired hollow brick, with reduced water absorption of 0.95% and 0.92% for stabilized 8% LP and fired hollow brick, respectively. Additionally, there was improved abrasion resistance of 0.46% as against 0.21% for stabilised and fired, respectively. Enhanced compressive strengths, reaching a maximum compressive strength of 2.145 MPa at 8% stabilization. Corresponding fired bricks achieved 15.035 MPa. Lime and pozzolana stabilization therefore, substantially improves unfired hollow clay brick performance, offering a viable low‑energy alternative to conventional firing for non-load-bearing and low‑rise construction, and contributing to reduced environmental impact of masonry materials. Finally, the study of fire resistance of the stabilized brick can be looked at in future research.