The expansive clayey soils show swelling-shrinkage behavior in wetting and drying cycles, respectively. The seasonal water content variations cause large volume changes of expansive clays, and consequently great losses on the infrastructure. In this study, the swelling-shrinkage behavior of a natural severely expansive clay was verified in its natural state and after being improved by nanosilica and industrial waste. Firstly, the swelling potential of the natural soil was determined, and then improvement impacts of different combinations of the stabilizers on the swelling potential were assessed by means of odometer tests. The results indicated that the swelling potential of 1-day-cured samples containing 0.5% of nanosilica decreased from an initial value of 75.26% for the natural expansive clay to 58.1%. The improvement by means of 0.5% of nanosilica and 20% of electric-arc furnace (EAF) slag decreased the swelling potential from an initial value of 75.26% for the natural expansive clay to 17.11%. Afterwards, the wetting and drying cycles’ effects on the swelling and shrinkage of the natural soil and that of the best identified combination of additives were verified by means of a modified odometer. The measurement of the axial deformation of soil, water content, void ratio, and saturation ratio during the swelling-shrinkage cycles indicated that the wetting and drying cycles caused the reduction of swelling potential of both natural and improved expansive soil samples. It was observed that the equilibrium condition occurred in lower number of wetting and drying cycles for the improved sample, compared to that of the natural soil. In addition, for the untreated samples, the highest void ratio and deformation variations occurred at saturation degrees between 50 and 90%. However, for improved soil sample, the highest void ratio and deformation variations were recorded at saturation degrees between 70 and 90%. In comparison with untreated expansive soil, occurring the highest void ratio and deformation variations at the higher saturation ratio reflected the reduction of negative effects of water content variations on volume changes when the expansive soil samples were improved. Based on the experiments performed on both the untreated and treated samples using the scanning electron microscope (SEM) and X-ray diffraction (XRD) tests before and after wetting and drying cycles, it was concluded that the additives used in the study decreased not only the swelling potential of highly expansive soil samples but also the swelling-shrinkage behavior of the soil. Additionally, it increased the durability of the samples during wetting and drying cycles.

膨胀黏土在湿润和干燥循环中分别表现出膨胀-收缩行为。季节性的含水量变化会导致膨胀粘土的体积发生较大变化，因此对基础设施造成巨大损失。在这项研究中，天然的严重膨胀粘土的膨胀-收缩行为在其自然状态下得到了验证，并经过纳米二氧化硅和工业废料的改善而得到了改善。首先，确定天然土壤的溶胀潜力，然后通过里程表测试评估稳定剂的不同组合对溶胀潜力的改善效果。结果表明，含有0.5％纳米二氧化硅的1天固化样品的溶胀潜力从天然膨胀粘土的初始值75.26％降低到58.1％。改进方式为0。5％的纳米二氧化硅和20％的电弧炉（EAF）炉渣将溶胀潜力从天然膨胀粘土的初始值75.26％降低到17.11％。之后，通过改进的里程表验证了润湿和干燥循环对天然土壤的膨胀和收缩以及添加剂的最佳组合的影响。在膨胀-收缩循环过程中对土壤轴向变形，含水量，空隙率和饱和度的测量表明，润湿和干燥循环导致天然和改良膨胀土样品的膨胀潜能降低。观察到，与天然土壤相比，改良样品的润湿和干燥循环次数较少时达到了平衡条件。另外，对于未经处理的样品，最高的孔隙率和变形变化发生在饱和度为50％至90％之间。但是，对于改良的土壤样品，在饱和度为70％至90％时记录了最高的空隙率和变形变化。与未经处理的膨胀土相比，当膨胀土样品改良时，最高的孔隙率和在较高饱和度下发生的变形变化反映出水分变化对体积变化的负面影响减少了。根据在润湿和干燥周期前后使用扫描电子显微镜（SEM）和X射线衍射（XRD）测试对未处理和已处理样品进行的实验，结论是，研究中使用的添加剂不仅降低了高度膨胀的土壤样品的溶胀潜力，而且还降低了土壤的溶胀-收缩行为。另外，它增加了样品在润湿和干燥周期中的耐久性。