Improved strength and reduced permeability of stabilized peat: Focus on application of kaolin as a pozzolanic additive

The aim of this work is to demonstrate the application of kaolin as a pozzolanic additive of stabilized peat. In addition to kaolin, Portland composite cement, calcium chloride and silica sand were used as the materials to stabilize the peat. To achieve such aim, test specimens of both untreated and stabilized peats were tested in laboratory in order to evaluate its unconfined compressive strength and rate of permeability. Each test specimen was prepared in such a way that it has to simulate the in situ condition of deep peat stabilization by deep mixing method. It was found that test specimen with 10% partial replacement with kaolin has the highest unconfined compressive strength that exceeds the minimal required unconfined compressive strength of 345 kPa. The test specimen was subjected to 100 kPa initial pressure and cured in water for 7 days. The unconfined compressive strength of the test specimen was discovered to be 33.7 times greater than that of untreated peat specimen. In laboratory permeability tests, the rate of permeability of untreated peat was found to be 6.43 × 106 times higher than that of stabilized peat. Samples of the test specimens were examined using Energy Dispersive X-ray (EDX) and Scanning Electron Microscope (SEM). High peaks of calcium element from the EDX results of stabilized peat specimens imply that the specimens have high calcium composition as a result of cement hydrolysis, and addition of kaolin is believed to induce secondary pozzolanic reaction in which the cementation crystals of mainly calcium silicate hydrate were formed to bind the soil. Based on the observation of SEM of the stabilized peat specimens, it was found that there was a significant pore refinement in the test specimens as a result of the filler effect of silica sand and pozzolanic activity of kaolin.

► Stabilized peat with kaolin has a high unconfined compressive strength.
► Initial pressure and curing duration affected the strength of stabilized peat.
► Binder and silica sand dosages influenced the strength of stabilized peat.
► Stabilized peat with kaolin has a very low permeability rate.
► Kaolin played a major role at refining the pores of stabilized peat.