THE WATER STABILITY AND MICROSTRUCTURE INDICES OF SULPHATE SALINE SOIL STABILIZED WITH LIME AND FLY ASH

Because of its low compressive strength and poor water stability, sulphate saline soil with much salt cannot be directly used in road embankment construction. It is proposed that sulphate saline soil be stabilized with lime and fly ash. As the stabilizing scheme for engineering purposes, adding lime of 6%, 8%, 10%, 12%, and 14% into sulphate saline soil according to a ratio(lime to fly ash) of 1︰1, 1︰1.5, 1︰2, 1︰2.5, and 1︰3 should be used in stabilizing sulphate saline soil. Unconfined compressive tests on stabilized soils and saturating stabilized soils were carried out to determine a suitable lime and fly ash content and a proper stabilizing scheme. SEM and EDS tests were completed to review the stabilized soil mechanism of lime and fly ash. The microstructure indices of stabilized soil were calculated to analyze the effect of lime and fly ash content on soil microstructure. The results have shown: (1)It is suitable to strengthen the water stability and strength of sulphate saline soil stabilized with lime and fly ash. With the increase of lime fly ash content, the strength of stabilized soils increases first and then decreases. (2)Gel materials and materials in needle-rod type are produced by the reaction of lime and fly ash, which fill into pores of the stabilized soil, enhancing the bonding force between the soil particles, thus increasing the strength and water stability of the stabilized saline soil. (3)The stabilizing scheme of 8% lime-24% fly ash is the most feasible. The stabilized soils have more aggregate particles, better elliptical particles, and a much more stable structure, which increase the compressive strength and water stability of stabilized saline soil, respectively. It has been proven that 8% lime and 24% fly ash can provide technical assistance for stabilizing sulphate saline soil in engineering utilization.