Evaluation of Naturally Occurring Aggregates as Subbase and Subgrade Construction Materials in Akwa-Ibom State, Southeastern Nigeria

An investigative study was conducted on some existing and potential natural aggregates sources in Akwa-Ibom State, Southeastern Nigeria. These aggregates are usually utilized in various construction works, but their suitability as subbase and subgrade construction materials is evaluated in this study. This is based on Nigerian Federal Ministry of Works, American Association of State Highways and Transportation Officials (AASHTO), and US Army Engineering Corp criteria. Most of the aggregates classified as A-2-4 materials; few classified as A-2-6. About 85 % of all the sampled materials satisfied the Nigerian Ministry criteria which are based like the AASHTO and US Army criteria upon particle size distribution, Plasticity Index, Liquid Limit, and California Bearing Ratio value. Possible interlayer interaction with respect to drainage characteristics was also investigated, although this does not form any of the criteria stipulated by the three agencies. A possible improvement to strength and drainage characteristics was also investigated.