Strength Characteristics of Oyster Shell Ash and Periwinkle Shell Ash Stabilized Lateritic Soil for Pavement Construction

Abstract

With an aim of contributing to the reduction of the greenhouse gas effect resulting from the incorporation of ordinary Portland cement as a binder material in construction and to further encourage the building of environmentally conscious structures using alternative binders, the strength characteristics of oyster shell ash and periwinkle shell ash as environmentally friendly additives to lateritic soil for pavement construction was investigated. Naturally occurring lateritic soil having a reddish-brown color was obtained from a borrow pit located at Ikorodu Local Government Area of Lagos State, Nigeria. The soil sample classified as SC and A-7-6 (5) using the Unified Soil Classification System (USCS) and AASHTO system respectively was treated with up to 15% oyster shell ash (OSA) and periwinkle shell ash (PSA) blend in a mix ratio of 60%: 40% by dry weight of soil and compacted using the West African Standard compaction effort. The results showed that consistency limits, compaction characteristics (optimum moisture content; OMC and maximum dry density; MDD) as well as strength properties (unconfined compressive strength; UCS, California bearing ratio; CBR, and Durability) improved with the addition of the OSA-PSA blend treatment. Peak UCS value of 556.44 kN/m² at 28-days air-curing was recorded at an optimal 9% OSA-PSA blend. Maximum unsoaked and soaked CBR values of 53.35% and 32.17% respectively were also recorded at an optimal 9% OSA-PSA blend. As specified in the Nigerian General Specifications for CBR values, the lateritic soil optimally stabilized with 9% OSA-PSA content and compacted using the WAS compaction energy can be utilized as a standalone stabilizer for fill material used for the rehabilitation of low-volume pavements. Additionally, the 9% OSA-PSA optimum blend can also be used as a standalone subgrade/base stabilizer during the construction of concrete/interlocked paved walkways. Furthermore, the utilization of OSA-PSA additive in the construction industry would significantly lead to a reduction in the challenges faced by the indiscriminate disposal of these shell wastes into the environment.