The Effect of Periwinkle Shell Ash (PSA) on Geotechnical Properties of Lateritic Soil for Road Construction Application

The study explores the enhancement of geotechnical characteristics of lateritic soil sourced from a popular burrow pit site in Kano State, Nigeria, by incorporating Periwinkle Shell Ash (PSA). The soil sample was mixed with 0 to 10% PSA content at 2% increment by dry weight of the lateritic soil. The prepared samples were subjected to natural moisture content, specific gravity, particle size analysis, Atterberg limits, compaction California bearing ratio (CBR), and unconfined compressive strength (UCS) tests following standard procedure outlined in BS1337 (1990), BS1924 (1990), and ASTM D3282. The soil is Classified as A-6(5) according to the American Association of State Highway and Transportation Officials (AASHTO) system. The soil underwent modifications upon the addition of PSA. Key findings include reduction the liquid limit from 36% to 32%. Concurrently, the plastic limit increases from 16% to 25%. Furthermore, the Maximum Dry Density (MDD) experienced a rise from 1.72 Mg/m3 to 1.82 Mg/m3 , while the Optimum Moisture Content (OMC) decreased from 15.34% to 11.55%. The unsoaked CBR also improved, moving from 26% to a peak value of 40%, indicating enhanced load-bearing capacity. The soil’s UCS significantly increased from an initial value of 44 kN/m2 to 133 kN/m2 before curing. The initial UCS increases to 164, 167, and 215 kN/m2 for curing period of 7, 14, and 28 days, respectively. All the improvements were achieved at the optimised percentage of 8% PSA content. The peak values of CBR and UCS at 8% PSA content satisfied the Nigerian General Specifications for Roads and Bridges (2016) criteria for sub-base materials, which stipulate a 20-30% range. This investigation underscores the potential of PSA as a viable soil stabiliser, promising substantial improvements in the geotechnical properties of lateritic soils for road construction purposes.