Mechanism And Long-term Stability Of Expansive Soil Stabilized With Fly Ash And Calcium Carbide Slag

The construction projects in expansion of land area often require improvementand reinforcement. Lime, fly ash and cement are commonly used as additives forthe expansive soil. By using industrial waste, such as fly ash, calcium carbide slagand other additives to improve the expansive soil, not only can improve theengineering properties of expansive soil, but also can achieve the benefits ofrecycling waste. However, the improved methods by using fly ash and calciumcarbide slag for expansive soil are not yet mature, especially its mechanism ofaction and long-term stability characteristics are not in-depth understanding, needfurther systematic study. In this paper, through the system laboratory test,focusing on the improved method to expansive soil by using industrial waste, suchas fly ash and calcium carbide slag, so as to master the engineering properties ofimproved expansive soil and reveal the microscopic mechanism of action. Throughthe wet and dry cycling test to the improved expansive soil, also can reveal itslong-term stability characteristics. The conclusions are as following:(1) For the physical characteristics, the two kinds of improved soil,20%flyash mixes with2%lime and10%calcium carbide slag, have remarkable effect.The improved soil is non expansive, its maximum dry density and optimummoisture content is lower than the undisturbed soil, which has good compactioncharacteristics.(2) For the strength characteristics, the intensity is increased with curingperiod to the improved soil. In the conservation of14d, it can be achieved betterimprovement. The improved soil with10%calcium carbide slag has the bestimprovement effect, followed by20%fly ash mixes with2%lime.(3) For the swelling characteristics, the deformation is weakened with thegrowth of the curing period. In the conservation of7d, it can be achieved betterimprovement. The improved soil with10%calcium carbide slag has the bestimprovement effect, followed by20%fly ash mixes with2%lime.(4) For the wet and dry cycling characteristics, the destruction of strengthcharacteristics and swelling characteristics have exacerbated with increasing the number of cycles to the fly ash improved soil. The improved soil with20%fly ashmixes with2%lime has remarkable effect.The swelling characteristics of the calcium carbide slag improved soil hasexacerbated with increasing the number of cycles, while the destruction of thestrength characteristics aren’t significantly in the early conservation. Theimproved soil with10%calcium carbide slag has remarkable effect.(5) For the micro-structural properties, due to the formation and developmentof the cementing material, the internal structure of the improved soil is tended todense; experienced wet and dry cycling, the cementing material is damaged andthe internal structure is no longer dense. The two kinds of improved soil,20%flyash mixes with2%lime and10%calcium carbide slag, have remarkable effect.