Synthesis and Characterization of a Novel Chemical Sand-Fixing Material of Hydrophilic Polyurethane
Zhiren WU, Weiming GAO, Zhishen WU, Kentaro IWASHITA and Caiqian YANG
Abstract:A novel chemical sand-fixing material of hydrophilic polyurethane resin, which was prepared by excessive MDI polymerizing with hydrophilic polyol, was studied in this paper. The structure of this sand-fixing material was characterized by termination with -NCO. It can react with water in several minutes to become a gel and a sand-fixing layer was formed by spraying the material on the sand surface. Several properties relating to the sand fixation were studied systematically, including curing time, permeability and porosity, mechanical properties, water retention capacity and durability from UV radiation. From the results, after 3 hours, the reaction rate of the sand-fixing materials was 95%, and after 4 hours, it was close to 100%. The curing time can be controlled by changing the temperature and concentration of the sand-fixing material according to the application for the best sand fixation effect. By increasing the amount of sand-fixing material sprayed on the sand, the thickness of the sand-fixing layer increased linearly. The relationship between the concentration and Yamanaka soil hardness was approximately linear. When the concentration of the sand-fixing material was 8%, the index of the layer reached to 28`29 mm. The compressive strength of the sand-fixing specimen was increased by increasing the concentration of the sand-fixing material, when the concentration increased from 3% to 7%, the compressive strength increased from 1.1 Mpa to 3.8 Mpa, respectively. When the sand-fixing material of hydrophilic polyurethane was sprayed on the sand, it basically formed a protective layer on the sand surface and prevented water vapor from penetrating. When the concentration of the sand-fixing material was more than 3%, the water retentive rate was more than 60% two weeks later, However, when the concentration was less than 3%, it was more than 80% in 6`8 days. Moreover, It is found that the amount of sediment decomposed by UV radiation increased almost linearly with increasing radiation amount. The lifetime of the sand-fixing layer is approximate 4`8 months. Key Words:Chemical sand fixation, Hydrophilic polyurethane, Sand-fixing material, Sand-fixing layer