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Role of fly ash in control of alkali induced swelling in kaolinitic soils: a micro-level investigation

Surprising heave behaviour in non-swelling kaolinitic soils is experienced in the recent years due to alkali contamination. The ever increasing number of reported failure of structures highlights the need to plan proper control for alkali-induced swelling. Thus, the present paper focuses on the utilisation of fly ash to control the swelling of three kaolinitic soils contaminated with highly concentrated alkali solutions. Different percentages of class F fly ash was used to reduce the alkali-induced swelling in soils. Results indicate that the kaolinitic soils contaminated with different concentrations of alkali solutions exhibited remarkable changes in swelling behaviour. Reduction in swelling was observed in all three soils under consideration. A reduction in swelling of about 68% was noted in red earth when treated with 20% fly ash. However, it was found that 10% fly ash was sufficient to control the undesirable swelling in case of ball clay and china clay. X-ray diffraction and scanning electron microscopy studies enlighten the mineralogical and morphological changes that occured in alkali-contaminated kaolinitic soils stabilised with fly ash.