Characterization and Modeling of Shrinkage Cracking of Cementitiously Stabilized Layers in Pavement
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This research identifies the properties of cementitiously stabilized materials that significantly affect shrinkage cracking in pavements with cementitiously stabilized layers. Methods for measuring these properties are recommended. The research approach consists of literature review, test procedure evaluation, and model development and calibration. Based on the test procedure evaluation, unconfined compressive strength, and indirect tensile strength and modulus tests are recommended. A suite of shrinkage-related tests is used to develop shrinkage cracking models; these tests include free drying shrinkage (including ultimate drying shrinkage), coefficient of thermal expansion, coefficient of friction, and restrained shrinkage cracking tests. Performance-related models are developed based on laboratory experiments, including strength and modulus growth models, and shrinkage cracking models. The strength growth models are developed based on extended testing at different curing times up to 360 days under standard curing conditions. Temperature and relative humidity are included in the growth models to assess indirect tensile strength and modulus values, which are critical to early-age shrinkage cracking and are sensitive to early-age curing conditions. Restrained shrinkage cracking tests are conducted on laboratory-scale beams. These results considering the effect of moisture gradient and drying shrinkage gradient along the depth of CSL are used to develop new mechanistic based shrinkage crack spacing and width models.It is found that neither the existing models nor the developed mechanistic based models can predict crack spacing and width in the field. Empirical shrinkage crack spacing and width models are developed based on dimensional analysis using field data.The developed shrinkage cracking models are recommended for incorporation into the Mechanistic-Empirical Pavement Design Guide, thus allowing for rational analysis and design procedures for pavements with cementitiously stabilized layers. The performance properties and their test procedures also are recommended. Three levels of material property characterization are provided. For those properties that do not have AASHTO or ASTM test methods, test procedures are drafted.