高庙子膨润土微观结构时效性试验研究

针对高庙子膨润土在不同含水率和不同干密度条件下的微观孔隙结构时效性进行了试验研究。首先采用静力压实法将3种不同含水率条件下的高庙子膨润土粉末压实到2种不同密实状态,压实结束后保持试样体积和含水率不变分别静置1,30,90d,然后分别采用压汞仪法和扫描电镜法对静置不同时间后试样的微观孔隙结构进行量测。试验结果表明,高庙子膨润土集合体间大孔隙随静置时间增加逐渐减少,而集合体内孔隙和小于压汞仪最小探测粒径的极小孔隙逐渐增多；随着静置时间的延续,膨润土微观孔隙结构趋于均匀化。产生上述现象的主要原因是：试样静置过程中,为达到吸力平衡,试样各微观孔隙结构中水分子重分布,导致层叠体内水分子层数增多,蒙脱石水化；随着水化的进行,层叠体晶层间水分子层数逐渐增多,同时厚的层叠体逐渐裂开成薄的层叠体,导致集合体内小孔隙增多；在体积不变条件下,集合体间大孔隙不断被挤压填充,孔隙体积逐渐减少。

Experimental study on ageing effects on microstructure of unsaturated GMZ01 bentonite

The ageing effects on the microstructure of GMZ01 bentonite with different water contents and dry densities are investigated. Firstly, GMZ01 bentonite powder with three different water contents is statically compacted to the designed dry densities. Then, the compacted samples under each initial condition are kept at constant volume and water content for various periods of time (1, 30 and 90 days). Afterwards, the aged samples are subjected to MIP and SEM tests respectively. The test results show that the inter-aggregate porosity decreases and the intra-aggregate porosity increases with the ageing time. The volume of the very thin pores not intruded by mercury also increases with the ageing time. The microstructure of the aged samples tends to be more homogeneous. These observations may be attributed to the smectite hydration induced by suction decrease of the compacted samples during the ageing process. With hydration, the water molecular layers between the interlayer spaces increase, and simultaneously, the large clay particles with many clay layers are split into smaller particles with fewer clay layers, creating a number of interparticle pores inside the inter-aggregates. Under the constant volume conditions, the inter-aggregate pores are gradually filled, resulting in the decrease of the volume of the inter-aggregate pores.