SHRINKAGE CRACKING OF SOILS AND CEMENTITIOUSLY-STABILIZED SOILS: MECHANISMS AND MODELING
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Shrinkage cracking of soil or cement soil can cause the infiltration or seepage of water into the material and lead to reflective cracking in the structure above it. Shrinkage cracking greatly limits the use of cementitious stabilization. Drying shrinkage is the major problem associated with shrinkage cracking. Although some studies on the drying shrinkage cracking of concrete have been carried out, few research efforts have focused on unsaturated soil and cement soil. Even fewer studies consider the shrinkage stress distribution and evolution of the stress profile during drying and/or cement hydration in shrinkage cracking modeling.Using two types of soil and two types of cement soil, this study investigates the soil and cement soil properties that are related to drying shrinkage and shrinkage cracking. These material properties, which are considered in this study to be dependent on pore relative humidity (RH) and/or cement hydration and, therefore, are neither uniform nor constant during drying and/or cement hydration, include the humidity isotherm, diffusion coefficient, soil water characteristic curve (SWCC), tensile strength, tensile stress-strain relationship, and shrinkage potential, etc. This study examines the effects of pore RH and/or cement hydration on these material properties. Models are developed herein to predict the evolution of these material properties during drying and/or cement hydration. By measuring the humidity isotherm and diffusion coefficient and using the finite element (FE) method, the evolution of the pore RH gradient within the soil or cement soil specimens during drying can be fully captured. A coefficient of moisture shrinkage is proposed to bridge the knowledge gap between pore RH and shrinkage potential, which is defined in this study as the maximum possible drying shrinkage of a material at a given pore RH when there is no restraint. Then, the pore RH and/or cement hydration-dependent tensile strength, tensile stress-strain relationship, and shrinkage potential within the specimens during drying and/or cement hydration can be fully understood using the models developed in this study. Finally, FE modeling case studies were conducted to verify the models and procedure proposed in this study to predict shrinkage stress and shrinkage cracking. The results were compared with results from laboratory experiments and good agreement was found.