Stabilization of Clay soil Using Cement and Volcanic Ash for Sustainable Pavement Structure

Abstract

A residual clay soil was collected at Bako village along Gwagwalada-Garki road in Federal Capital Territory of Nigeria using the method of disturbed sampling. The clay was characterized and microstructural tests including X-ray diffraction (XRD) test, Scanning Electron Microscopy (SEM) test and Electron Dispersive Spectroscopy (EDS) tests were also conducted on the clay soil. The clay was then compacted at Standard Proctor energy level to obtain the maximum dry density (MDD) and optimum moisture content (OMC). Unconfined compressive strength (UCS) tests were then conducted on the natural clay and clay mixed with 0, 2, 4 and 6% cement which are in turn admixed with 0, 3, 6, 9, 12 and 15% volcanic ash (VA) each. Results showed that the clay classified under clay of high plasticity (CH) based on unified soil classification system. The clay also consists majorly of montmorillonite, ankerite, calcium silicide, anorthite, anothoclase and orthoclase minerals. The SEM test revealed flaky nature of the clay with pore spaces. The natural clay specimen compacted at standard proctor energy level mixed with varied composition of VA showed 2.5 times increase in UCS compared to the value of the natural clay. For clay made of 6% cement with varied percentage VA, the UCS increased by 80% compared with UCS of specimen containing 6% cement-0% VA. The optimal VA value for maximum UCS values lies between 6% and 9% VA.