Development of ecoefficient composite bricks from river sediments and snail shell waste

Abstract

The increasing global demand for fired clay bricks has spurred a search for sustainable alternatives due to clay shortages. This study explores the potential of the N’Fis river deposit as an environmentally friendly material for brick production. It also examines the incorporation of snail shells into the deposit, with percentages ranging from 0 to 100% (by weight), fired at 900, 1000, and 1200 °C. Analyses included particle size distribution, carbonate content, Loss-On-Ignition, weight reduction, X-ray fluorescence, X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectrometry, and Atterberg limits. Mineral analysis showed that the deposit contains ⁓40% clay (illite 27%, kaolinite 7%, chlorite and smectite 3% each), quartz (24%), feldspar (20%) and carbonates (15%). These values indicate moderately plastic materials suitable for clay bricks. The high carbonate content in snail shells causes greater weight loss during firing, increasing porosity and reducing mechanical strength. Compressive strength declined from 24.6 MPa (pure deposit) to 14.5 MPa (50 wt% snail shell) but still exceeded the minimum requirements of 10 MPa and 4 MPa specified in standard EN 772-1 and Moroccan norms, respectively. Thermal conductivity decreased from 0.77 to 0.20 W/m K with higher shell content, improving insulation. Bulk density also decreased, producing lightweight bricks. An increase in porosity lowers density and thermal conductivity, thereby enhancing insulation, but simultaneously reduces mechanical strength and increases water absorption. The combined use of river deposits and snail shells offers an economical and eco-friendly alternative for enhancing physico-mechanical and especially thermal properties of fired clay bricks. This approach also contributes to reducing environmental pollution and degradation.