Mechanical Characterization of a Composite Mortar Made from Lateritic Soils Stabilized with Autogenous Welding Lime and Reinforced with Palm Kernel Cake (PKC) for the Production of Compressed Earth Bricks (CEBs)

Abstract

Sustainable construction in sub-Saharan Africa is confronted with a dual requirement: meeting a high demand for housing while reducing the carbon footprint of the building sector. In this context, this study investigates the mechanical performance of a composite mortar based on local resources, combining four lateritic soils from Benin, lime derived from autogenous welding (an artisanal by-product), and palm kernel cake (PKC) fibers, an agricultural waste. The experimental program, structured in two phases, is based on lateritic soils from Zogbodomey, Dassa-Zoumè, Glazoué, and N’Dali, representative of the pedological variability of Benin, with complementary X-ray diffraction (XRD) analyses used to establish relationships between mineralogy and performance. The first phase assesses the influence of lime content (0% to 30%) on compressive strength at 7, 14, and 28 days, as well as flexural strength at 28 days, while the second phase introduces PKC contents (0.25% to 2%) into the optimal formulation. The results show that a 20% lime content is optimal, with 28-day compressive strengths ranging from 4.58 to 5.51 MPa. The lime exhibits a high portlandite content (85.4%), ensuring strong reactivity, while the N’Dali soil is characterized by the presence of kaolinite (26%). The incorporation of 1% PKC improves compressive strength (up to 8.5%) and, more significantly, flexural strength (up to 66%), indicating pseudo-ductile behavior associated with crack-bridging mechanisms. The optimal formulations exceed the 4 MPa threshold required for load-bearing masonry and exhibit performance comparable to a reference cement mortar, thereby opening promising prospects to produce sustainable compressed earth blocks in Benin, within a circular economy framework and a strategy aimed at reducing CO 2 emissions.