水泥改性膨胀土基本特性试验

Experiments on basic characteristics of cement-modified expansive soil

通过无侧限抗压强度试验、收缩试验、X射线衍射(XRD)试验、压汞(MIP)试验、扫描电镜(SEM)测试,从宏观力学特征、物相构成演变以及微观结构特性三方面,对水泥改性膨胀土进行系统研究。结果表明:掺入水泥可以有效改善膨胀土的土体强度和胀缩特性;掺入水泥使得膨胀土微观结构发生显著变化,随水泥掺入量的增加,水化反应产生的C-S-H凝胶态产物总量逐渐增多,将土体颗粒粘联胶结形成较大的絮状体,优化土体孔隙结构,改性膨胀土土体内孔径小于100 nm的微细孔体积分数逐渐增大,说明水化产物的总量是决定水泥改性膨胀土微观孔隙结构特征、土体强度及收缩特性的关键因素。

Through the unconfined compressive strength test,shrinkage test,X-ray diffraction(XRD)test,mercury injection porosimetry(MIP)test and scanning electron microscopy(SEM)test,the cement-modified expansive soil was systematically studied in the aspects of macroscopic mechanical properties,phase evolution and the micro-structure characteristics.The results show that cement addition can effectively improve the strength,swelling and shrinkage characteristics of expansive soil.After the cement addition,the microstructure of expansive soil changes significantly,and the gel phase hydration products of C-S-H during hydration reaction increase with the cement content.The soil particles can form a larger flocculent body and can benefit the pore distribution.The volume fraction of micro holes(diameter less than 100 nm)in modified expansive soil increases,indicating that the amount of hydration products is the key factor to soil strength,microscopic pore structure characteristics and shrinkage characteristics of cement-modified expansive soil.