Determining Soil Minerals Composition From Soil Plasticity Characteristics Investigation: A Case Study of Uwelu Spare-Parts Market Scrap Dumpsite, Benin

Abstract

The plasticity properties of soil, largely influenced by its mineralogical composition, are crucial in determining its performance in engineering projects and its suitability for construction and agriculture. This research explores the correlation between soil mineral content and Atterberg limits—specifically, the Liquid Limit (LL), Plastic Limit (PL), and Plasticity Index (PI)—through laboratory testing of three distinct soil samples (Samples 1, 2, and 3) from Uwelu Auto Spare parts market Scrap dumpsite. Findings from the statistical interpretation of the laboratory test results show notable differences in plasticity among the samples. Sample 1 displayed a shift from non-plastic (PI = 3.1%) to moderately plastic (PI = 15.0%), pointing to a combination of silt and low-activity clay minerals such as kaolinite. Sample 2 had high plasticity (PI ranging from 9.1% to 16.4%), characteristic of expansive clays like montmorillonite, which are problematic in construction due to their swelling behaviour. Sample 3 exhibited moderate plasticity (PI = 6.8–11.6%), reflecting a balanced mix of clay and silt, likely containing kaolinite or chlorite. The study emphasizes how mineralogy governs soil-water interactions: soils rich in smectite tend to have higher LL and PI values because of their expansive traits, whereas kaolinite-rich soils demonstrate lower plasticity. These insights have practical implications for geotechnical engineering, such as the need to stabilize high-PI soils and the appropriateness of low-PI soils for use as subgrade material. Ultimately, the research highlights Atterberg limits as useful indirect indicators of soil mineral composition and reinforces the importance of standardized laboratory testing in predicting soil behaviour. The findings contribute to improved understanding of soil plasticity, supporting more informed engineering decisions and sustainable land management strategies.