Effect of Ceramic Waste Valorization on the Stabilization of Tori-Dokanmey Ferralitic Soil for Road Pavement Layers in Benin

Abstract Bar soil (locally known as “terre de barre”, a ferralitic soil common in southern Benin), a ferralitic material abundantly available in southern Benin, offers a low-cost local resource but exhibits poor geotechnical performance, particularly low bearing capacity and high sensitivity to water, making it unsuitable for road construction. This study investigates the stabilization of bar soil through the incorporation of pulverized ceramic waste (broken tiles), ground and sieved to 0.08 mm, in proportions ranging from 2.5% to 15% by weight. Geotechnical characterization tests were conducted in accordance with current ISO and French standards. The results demonstrate a significant improvement in the treated soil’s properties. While the untreated bar soil contains 48% fines and fails to meet the Experimental and Study Center for Building and Public Works (CEBTP) specification limits, the addition of 7.5% ceramic waste reduces fines to 28%, enhancing the particle size distribution. Furthermore, the plasticity index decreases to 13 at 12.5% ceramic content, and the maximum dry density reaches 2.10 t/m³ at 15%, exceeding the minimum threshold of 1.90 t/m³. The California Bearing Ratio (CBR), a key indicator of load-bearing capacity, increases from 23% for raw soil to 48% at 15% ceramic waste, qualifying the material for use in sub-base layers under traffic classes T1 to T5. Based on these findings, an optimal ceramic waste content between 7.5% and 15% is recommended. This approach offers a technically effective and economically viable solution aligned with CEBTP design guidelines 1984, revised in 2019.