Abstract: Shrinkage cracking of pavement subbase layers is regarded as a major distress in the construction of pavements, especially for expansive soils. To solve the problem, polymeric soil stabilizing agents are widely used in construction engineering, because of its ability to improve the mechanical properties of soil, such as reducing shrinkage cracking and structural failure of pavement subbase layers. Additionally, bentonite usually be used as the clay specimen due to its high shrinkage potential while drying. In this research, two chemical stabilizing agents, hydrophilic and hydrophobic polyurethane were mixed with bentonite at different weight ratios, and the water content change were monitored over time. The performance of each chemical agent was also quantified by the image process. The results show when PU foam was added at a relative low weight ratio (< 5%), 3%~5% more water can be retained inside samples, and hydrophilic PU foam has a greater performance than hydrophobic PU foam at the early stage. However, there are potential problems including earlier cracking and de-polymerization of hydrophobic PU foam, when using the chemical stabilizing agents in bentonite, which are also illustrated in this paper.
Authors: Xijin Zhang, Xiong Yu, Yuan Guo, and Xudong Fan
Keywords: Bentonite, Hydrophilic, Hydrophobic, PU foam, Image process, Potential problems