Study On The Test Method And Mechanism For Drying Shrinkage Of High Performance Cement

At present, all over the world shows the increasing demand of cement and concrete of superior engineering quality and shows great concern about the problems of its immense consumption of energy and natural resources and burden of the environment. To ensure the sustainable development of cement and concrete materials, it is taken as one of the important project of state 973 plan to study on preparation and application of high performance cement.When concrete is under low humidity conditions, its volume will contract and distort due to moisture loss. Drying shrinkage is one of the main causes of cracking in concrete structures. Drying cracks reduce the durability of concrete structures and sometimes lead to a concrete structure destroyed. Drying shrinkage of concrete structures is mainly caused by the drying shrinkage of cement paste. To guide the preparation and manufacture of high performance cement, it is important to research on the drying shrinkage character and mechanism of cement, to optimize structure model.A reasonable and feasible test method for drying shrinkage of mortar called improved method was first determined from several aspects in comparison with current standard JC/T method. Using improved method to measure drying shrinkage, simultaneously using TG-DSC, chemical bound water, pore structure and pore size distribution of hydrated cement mortars, NMR and IR analysis, influence of key parameters on drying shrinkage of cement was studied; The strength, Drying shrinkage dynamics, and drying shrinkage process of high C3S Cement System were studied; the relationship between the microstructure, composition and drying Shrinkage of cement pastes was also studied; Measures to reduce drying shrinkage cracking of cement based materials were proposed. The results indicate:The drying shrinkage values of cement mortars tested by the improved method keeps a well linear correlation with that of JC/T method. There is more clear relationship between drying shrinkage at 28 days tested by the improved method and...