Suitability of Some Nigerian Pyroclastics as Construction Materials

This work investigates, by means of geological and geotechnical analyses, the potentials of the Abakaliki pyroclastic (volcanic) bodies within the Abakaliki Metropolis (southeastern Nigeria) as construction materials for various engineering projects. Modal analysis indicates that pyroclastics are fine-grained to porphyritic tuffs, with high amount of plagioclase, glassy groundmass and shaley lithic fragment, and alkaline/basaltic in composition. Comparison with construction standards indicates that the Abakaliki Pyroclastics will perform marginally to fairly well for most construction purposes, such as construction stones, amour stone or rip-rap, as well as concrete and road aggregates; most of the tested samples have geotechnical parameters values outside recommended limits. The poor to marginal performance of the pyroclastic aggregate in the laboratory may be explained by high amount of weak and deleterious minerals (shaley lithic fragment, volcanic glass and chlorite) which suffer material deterioration over engineering time, especially when exposed to adverse climatic factors (high volume of rainfall and high and fluctuating temperature) as is the case in the tropics.