YANG Yong, ZHANG Shuqing, RONG Hui, ZHANG Lei, ZHANG Ying, XU Rui, WANG Xueping, YANG Jiujun
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The current research on the lime, slag, fly ash and other soil modifiers is mainly in the macroscopic properties such as mechanical properties and durability. In this paper, the microscopic angles such as the mineral composition, the functional group peaks and microstructures before and after the modification of the modified materials are attempted to illustrate the intrinsic mechanism of soil modification. The test results show that when the lime was added alone, the modification effect of the raw soil increased with the increase of lime content. The optimum dosage was 10%, and the 28 d compressive strength and softening coefficient respectively reached 3.69 MPa and 0.80, because the platy Ca(OH)2 hydration product filled the voids between the raw soil particles, and the saturated Ca(OH)2 only had its skeleton effect. When 10% lime was separately doped with 5% slag and 5% fly ash, the compressive strength of 28 d increased by 8.1% and 2.4% respectively, and the softening coefficient reached 0.92 and 0.90 respectively, because the secondary hydration reaction of fly ash and slag occurred, among which Mg—O, Al—O and other bonds were broke. The substitution of cations such as Al3+ and Mg2+ were displaced from Ca(OH)2, causing the peak position at 1 436.47 cm-1 to shift to near 1 400 cm-1, and the CSH gel characteristic peak around 1 030 cm-1 and the characteristic peak of volcanic ash reaction around 3 120 cm-1 appeared. The modification effect of slag-added slag was better than that of single-mixed lime, and the modification effect of complex fly ash was not good.