胡敏酸对水泥土强度的影响及机理

On the strength of cement soil affected and effected by the humic acid and its mechanism

针对实际工程中胡敏酸造成水泥土搅拌桩强度降低的问题,利用室内试验研究不同胡敏酸掺入量、不同水泥掺入比制备的水泥土试样以及在不同养护龄期下水泥强度的变化规律,基于扫描电镜(SEM)和能谱分析(EDS)的检测结果,分析胡敏酸对水泥土试样强度的影响机理。结果表明,1)水泥土试样的无侧限抗压强度随着胡敏酸质量分数的增大而减小,其峰值应力处的应变也随着胡敏酸质量分数的增大而降低;水泥土试样的无侧限抗压强度随着养护龄期的增大而增大;水泥土试样的无侧限抗压强度随着水泥质量分数的增加而增大,但随着胡敏酸质量分数的增大,低水泥质量分数的无侧限抗压强度增幅较小。2)通过对扫描电镜观察和能谱结果的分析,添加胡敏酸制备的水泥土试样,微观结构变松散,土颗粒周围的胶结物质减少;水泥质量分数较低时孔隙较多且较大,孔隙随着水泥掺入比的增大而减少,水泥结构变得更为密实;水泥土试样中水泥的水化产物即水化硅酸钙(C—S—H)与水化铝酸钙(C—A—H)随着胡敏酸质量分数的增大而减少,其微观结构中水泥的水化产物减少,能谱分析中水泥土的Ca质量分数减小,其宏观上表现为水泥土无侧限抗压强度降低。

The given paper is aimed at analyzing the strength reduction of the cement pile mixed with soil and stabilized by humic acid in common practical engineering projects.For the said purpose,we have conducted lots of experiments of the influential mechanism of humic acid accordingly with the strength of the cement stabilized soil samples through different ratios of humic acid content and different ratios of cement content through scanning electron microscope(SEM) and energy spectrum analysis(EDS).The above said experimental results show that:(1) The unconfined compressive strength of the cement stabilized soil samples tends to decrease gradually with the content increase of the humic acid,whereas the strain at the peak stress tends also to decrease gradually with the increase of the humic acid content.What is more,the unconfined compressive strength of the cement stabilized soil samples also tends to increase gradually with the increase of the curing age.Besides,the unconfined compressive strength of the samples of cement stabilized soil tends to grow up with the increase of the cement content,though the increase rate of the humic acid content and that of the unconfined compressive strength is also small with the low cement content;And,(2),The microstructure of the cement stabilized soil samples prepared by adding humic acid tends to get loose due to the decrease of the cementing substances around the soil particles through observation via the scanning electron microscope and energy spectrum analysis.What is more,when the cement is small in content,there would appear bigger pores.But,in spite of the gradual decrease of the pores with the increase of cement ratio addition,the structure tends to get denser.The hydration products in the cement tend to promote stabilization of the soil samples,such as the calcium silicate hydrate and the calcium aluminate hydrate.At the same time,the decreasing rate tends to get gradually minor with the increase of humic acid content.And,the Ca content of the cement stabilized soil may tend to decrease in the energy spectrum analysis.In addition,the stabilized soil can help to reduce the cement hydration products in the microstructure of the cement,which clearly demonstrates that the unconfined compressive strength of the cement stabilized soil may decrease from the macroscopic point of view.