Experimental investigation on water retention property of rubble improved by modified hydrophilic polyurethane

Rubble is distributed in discarded spoil sites of engineering construction, mining sites and rocky desertification regions in arid land. Due to the extremely poor water retention capacity of rubble, vegetation restoration proves to be highly challenging in these areas. A type of modified hydrophilic polyurethane material (W-OH), which can effectively improve water retention capacity, shows potential in enhancing the water retention of rubble. In this study, the water desorption and absorption properties of W-OH gel, the influence of temperature on these gels, and the water retention properties and microstructure of rubble improved by W-OH were comprehensively investigated by laboratory tests. The test results showed that the water retention of W-OH gels was dependent on concentration. As the concentration of W-OH solution increased, the desorption rate of the gels decreased, while the residual water content ratio increased, indicating better water retention. The gels possessed a strong water absorption capacity, with higher concentrations leading to greater absorption. Temperature affected the water desorption of W-OH gels. Specifically, higher temperatures resulted in a shorter desorption duration and a higher desorption rate, reducing the water retention capacity. The difference in water retention among gels of different concentrations was more distinct at lower temperatures. The water retention capacity of rubble improved by W-OH was enhanced compared with the original rubble. As the W-OH concentration increased, the initial volumetric water content of the improved rubble decreased, while the residual volumetric water content increased. Microscopic analysis revealed that rubble particles were obviously wrapped and cemented, the pores in the rubble were filled, the pore volume was reduced and the internal structure was enhanced, which contributed to improved water retention. Overall, W-OH showed great promise in improving the water retention of rubble slopes, offering a potential solution for ecological restoration in such areas.