气泡混合轻质土的耐久性与劣化机理研究

Air-foam treated lightweight soil is a ground material prepared by mixing air bubbles and water with soil and cement, which is light in self-weight, strength and density are adjustable, self-standing, and has been widely used in engineering. The water content and density would be increased in long-term soaking conditions, thereby losing the characteristics of light and cause freeze-thaw resistance and wet dry cycling performance decreases, so it is very important to improve the durability of air-form treated lightweight soil for its application. Firstly, the water absorption, permeability, freeze-thaw resistance, anti wet dry cycling performance, and the water absorption of air-form treated lightweight soil after freeze-thaw and wet dry cycling will be investigated by laboratory tests, then the intrinsic correlation mechanism between water absorption and freeze-thaw resistance, wet dry cycling performance of air-form treated lightweight soil will be revealed. Secondly, the characteristics of bubbles and its variation under different conditions will be investigated by scanning electron microscopy experiments, mercury test and fractal theory, then the deterioration mechanism of air-form treated lightweight soil under freeze-thaw and wet-dry cycle conditions will be revealed from the micro-level. Finally, preparing the air-form treated lightweight soil with lower water absorption based on the effect of characteristic of air-form on the water absorption. Research results will be help for the popularization and application of air-form treated lightweight soil.

气泡混合轻质土是由原料土与一定比例的固化剂、水、气泡等混合搅拌而成的轻型填土材料，具有轻质、强度和密度可调节、自立性好、流动性好等优点，在工程中已得到较为广泛的应用。气泡混合轻质土在长期浸水条件下含水量会提高、密度会增大，进而失去轻质特点及引起抗冻融性能和抗干湿性能的降低，所以掌握并提高气泡混合轻质土的耐久性对其推广应用极为重要。本项目拟通过室内试验研究气泡混合轻质土的吸水性、渗透性、抗冻融和抗干湿循环性能，以及冻融和干湿循环作用后的吸水性，揭示气泡混合轻质土的吸水性与其抗冻融循环性能、抗干湿循环性能之间的内在关联机制；通过扫描电镜试验和压汞试验，基于分形理论，研究轻质土中的气泡特征及其在各条件下的变化规律，从微观层面揭示冻融、干湿循环作用下气泡混合轻质土的劣化机理；基于气泡特征对轻质土吸水性的影响规律，研究制备低吸水性的气泡混合轻质土,为气泡混合轻质土的推广应用提供理论和技术支撑。

气泡混合轻质土是由原料土与一定比例的固化剂、水、气泡等混合搅拌而成的轻型填土材料，具有轻质、强度和密度可调节、自立性好、流动性好等优点，在工程中已得到较为广泛的应用。气泡混合轻质土在长期浸水条件下含水量会提高、密度会增大，进而失去轻质特点及引起抗冻融性能和抗干湿性能的降低，所以掌握并提高气泡混合轻质土的耐久性对其推广应用极为重要。项目组围绕气泡混合轻质土的耐久性问题，通过试验和理论分析开展研究，首先提出了利用温差制备气泡混合轻质土的方法，并研制了一种可测试干湿循环/冻融循环作用后气泡混合轻质土渗透性的试验装置和新型的发泡剂；干湿循环和冻融循环作用都会引起气泡混合轻质土吸水率和渗透系数的增大和抗压强度的降低，其中冻融循环的影响更大。影响冻融循环对气泡混合轻质土作用强弱的重要因素是初始含水率的大小，可通过掺入硬脂酸钙或粉煤灰降低气泡混合轻质土的吸水性。本项目的研究成果可为气泡混合轻质土性能的提升和推广应用提供理论基础，具有重要的科学意义和工程应用价值。