Geotechnical evaluation of the quality and durability of argillites from Abakaliki Metropolis (Southeastern Nigeria) as road aggregates

To evaluate the quality and durability of crushed aggregates for certain engineering applications, better knowledge of their mineralogical and chemical characteristics and physico-mechanical properties become very imperative. In this present study, using X-ray diffraction technique along with chemical analysis, representative samples of argillite were tested for mineral compositions, and basic geotechnical tests were used to evaluate their physical and mechanical properties to ascertain their suitability as road aggregates. The results from evaluated properties were compared with the acceptable criteria in national and international usage. Statistical relationships existing between the physical and mechanical properties were described using simple regression analysis. From the results, the mineralogy and chemical characteristics revealed the predominance of quartz, illite, and feldspar reflected in the relatively high silica, aluminum, and alkali contents in the average chemical analysis. The low absorption capacity and high specific gravity influenced positively the mechanical strength. The aggregate crushing, aggregate impact, and Los Angeles abrasion values were generally lower than the maximum allowable value of 30%, an indication that the aggregates, in addition to having sufficient strength to withstand high stresses, have high resistance to impact and abrasion. The high 10% fines values of over 150 kN indicate strong and durable road materials suitable for many special engineering uses. The argillite indicates good road material that can offer significant economic and environmental benefits but would require informed caution. The argillite aggregate high strength and attrition resistance with its cheaper abundance will continue to be prominent factors in its utilization for road projects.