Magnesium Salt Influenced Strength Behavior of Lime-Fly Ash Stabilized Fine Grained Soil

Abstract

The fine grained soil subgrade in coastal areas has the characteristics of high underground water level and serious salinization, and the lime-fly ash stabilized soil (LFSS) often used as the road base material. In order to study the effect of magnesium salt on the material strength, 5 % MgCl₂ solution was used to simulate the groundwater magnesium salt environment, and specimens with 7 d, 14 d, 28 d, 60 d and 90 d curing ages were tested in MgCl₂ solution for 1 d, 5 d, 10 d, 15 d or 30 d. A controlled test was also conducted in purified water. Strength mechanism of LFSS was analyzed; SEM test was taken; and the influence mechanism of MgCl₂ medium was analyzed. The results showed that MgCl₂ medium, immersing time, and curing age have effects on compressive strength of LFSS. More specifically, although the early strength is low, the strength of LFSS maintains slow and steady growth from 7 d to 90 d. Long-term immersing in both MgCl₂ solution and purified water will reduce the strength of LFSS, while the strength of specimen immersed in MgCl₂ solution will decrease faster. Reactions between MgCl₂ and LFSS destroyed the original gels and crystals, causing a negative impact on the strength of LFSS. However, with the test dose of MgCl₂, the reduced strength of LFSS can still satisfy the sub-base requirement of second-class highway in China.