Simulation on strength and thermal shrinkage property mechanisms of pre-cracked cement stabilized crushed stone

For the problem that the cement stabilized crushed stone tends to develop cracks, thus reducing the service life of pavements, an idea based on the coarse aggregate pretreatment technology was proposed to improve the pre-cracked cement stabilized crushed stone material. Some coarse aggregates of the cement stabilized crushed stone were pretreated to make their surfaces coated with a layer of new material, and thus a new interface was formed, to alleviate the influence of reducing cracks on the overall uniformity of the material during the shrinkage process. Then, the strength properties and the internal mechanism of crack development under the thermal shrinkage of new material were analyzed through simulations. A simulation model of the pre-cracked cement stabilized crushed stone was built based on the discrete element method. The virtual unconfined compression tests and restrained thermal shrinkage and cracking beam tests were conducted, respectively. Research results show that under the premise that the pretreatment of coarse aggregates only affects the interface strength of coarse aggregates, there is a good linear correlation between the unconfined compressive strength of the specimen and the two key parameters including the interface strength ratio, as well as the pretreated coarse aggregate replacement ratio. The unconfined compressive strength can be calculated and predicted through the regression formulas. When the interface strength ratio is higher than 40%, the increase in the pretreated coarse aggregate replacement ratio will only reduce the material's strength and cannot avoid the locally transverse cracks. When the interface strength ratio is lower than 40%, the cracks appearing during the shrinkage process of the specimen will change from the locally transverse cracks to the evenly distributed micro-cracks as the pretreated coarse aggregate percentage increases, thus ensuring the overall uniformity of the material after the shrinkage cracking. When the interface strength is less than 30% of that of the untreated material, and the coarse aggregate replacement ratio is higher than 30%, the internally transverse cracks of the specimen will be effectively reduced, and the thermal shrinkage cracking of the cement stabilized crushed stone can be alleviated.