Stabilization of compacted clay with cement and/or lime containing peat ash

Abstract

Soft clay is problematic due to its settlement, swelling and strength issues, when applied as road embankment material. This paper investigates the possibility of the use of cement and/or lime for improvement ground of shallow clay to support highway embankment. A novel approach to stabilize the clay is to use peat ash as a supplementary material in the compacted and stabilized soil. It is worth noting that research on the application of peat ash as a pozzolanic material in stabilizing soft clay is relatively scarce. The objectives of this research are: (i) to stabilize the compacted clay with cement and/or lime, peat ash and silica sand in the laboratory and (ii) to evaluate the effect of binder dosages on short-term and long-term strength of stabilized soil. To this end, the stabilized soil specimens with the highest maximum dry density were chosen for further evaluation under laboratory unconfined compression tests. In addition, the chemical compositions of materials and microstructure of the stabilized clay were examined using X-ray Fluorescence and Scanning Electron Microscope (SEM), respectively. It was found that, the optimal mix design of the stabilized soil is 14% cement, 12% peat ash and 5% silica sand. SEM analysis suggests that the cementitious products were increased with cement and peat ash dosages and clogged the pore spaces. It was further revealed that, partial replacement of cement with 12% peat ash in the optimal mix design resulted in maximum unconfined compressive strength. In summary, a notable discovery is that the partial replacement of cement with 12% peat ash in the optimal mix design can be sustainably applied in order to stabilize the clay without failure. Meanwhile, it has been observed that cement content higher than the lime content enables a better homogeneity of the stabilization, enhancing the strength development in the stabilized soil.