Experimental Study On Properties Of Bound Water In Clay

Clay minerals can interact with water molecules to form bound water on the surface of the particles.The combined water has an important influence on the physical properties of clay,such as plasticity,expansion and contraction,as well as mechanical properties such as strength and deformation.This research is of great importance for improving the engineering properties of clay.Based on main controlling factors and hydration mechanism of each stage of clay mineral hydration to analyze the content of the surface bound water of clay and divided the boundary of different types of combined water.On this basis,the self-formed ionic soil stabilizer was used to modify the bound water on the surface of the clay soil.This paper mainly combines experiments with theoretical analysis.The outline of the research achievements of this thesis are listed as follows:(1)According to the principle of total hydrophilicity,test methods for dynamically observing the interaction between clay and water molecules were established,namely isothermal adsorption test and thermal analysis test.The principle and method of tests are clarified.It is also proposed to reduce the concentration of loosely bound water on the surface of the soil particles by reducing the concentration of hydrated cations around the soil particles.Thereby improving the engineering properties of the clay.(2)The isothermal adsorption tests of several typical clay minerals at 23°C showed that whenp/p_s>0.9,the adsorption amount of water increased sharply and the density of hydrated clay and bound water on the surface of the soil particles changed obviously,which means that the type and property of the water adsorbed on the surface of the clay particles has changed and the pointp/p_s=0.9 is the boundary between firmly bound water and loosely bound water.(3)The type and boundary of water in clay minerals were qualitatively demonstrated by thermogravimetric analysis and differential scanning calorimetry.The results show that free water,loosely bound water and firmly bound water in hydrated clay corresponds to different thermal reaction temperature ranges,namely 25~75°C,75~120°C,120~230°C.Under heating conditions,different types of water will be removed in different thermal reaction temperature ranges.(4)Modify the montmorillonite via ionic soil stabilizer.The lowest plasticity index and the lowest osmotic combined water content were used to evaluate the reinforcement effect of different concentrations of ionic soil stabilizer for the test montmorillonite.The zeta potential test,free expansion rate test and direct shear test were carried out on the soil samples before and after curing.The results show that the ionic soil stabilizer can reduce the thickness of the electric double layer of montmorillonite particles,reflecting the combination water film turned to thin,the cohesion and shear strength of the soil increased,and it also inhibits the expansion of montmorillonite effectively.