Use of high volume fly ash cement for stabilization of expansive soils with high soluble sulfates content

Expansive clays are usually chemically stabilized with cement or lime to reduce their plasticity and volume change potential, and improve other properties. However, if the soils are rich in soluble sulfates, the calcium in the lime (or liberated during cement hydration) can react with the sulfates to produce ettringite and/or thaumasite. These minerals can undergo significant expansion, causing severe damage to structures and pavements.; A practical way of reducing the swelling potential due to sulfate attack appears to be a reduction in calcium hydroxide. The results of the experimental program conducted in this study suggest that Class F fly ash can be effective in chemically binding calcium hydroxide into cementitious products by boosting the pozzolanic activity, making it less available to react with sulfates to form the gypsum necessary for the formation of expansive minerals.