Mechanical Activation of a Waste Material Used AS Cement Replacement in Soft Soil Stabilisation

Waste materials, sometimes called by-product materials have been increasingly used as replacement materials to reduce the usage of cement in different construction projects. In the field of soil stabilisation, waste materials such as pulverised fuel ash (PFA), biomass fly ash (BFA), sewage sludge ash (SSA), etc.; have been used since the 1960s. In this study, a particular type of a waste material (WM) was used in soft soil stabilisation as a cement replacement combined with the effect of mechanical activation, using grinding, to enhance the performance. The stabilised soil in this study was an intermediate plasticity silty clayey soil with medium organic matter content. The experimental investigations were conducted to find the optimum content of WM by determining the Atterberg limits and the unconfined compressive strength (UCS) of soil samples containing (0, 3, 6, 9, 12, and 15%) of WM by the dry weight of soil. The UCS test was carried out on specimens exposed to different curing periods (zero, 7, 14, and 28 days). Moreover, the optimum percentage of the WM was subject to different periods of grinding (10, 20, 30, 40mins) using a mortar and pestle grinder to determine the effect of grinding and its optimum time by conducting UCS tests. The results indicated that the WM used in this study improved the physical properties of the soft soil where the index of plasticity (IP) was decreased significantly from 21 to 13.10 with 15% of WM. Meanwhile, the results of UCS test indicated that 12% of WM was the optimum and this percentage developed the UCS value from 202kPa to 700kPa for 28 days of curing. In terms of the time of grinding, the results revealed that 10 minutes of grinding was the best for mechanical activation for the WM used in this study