Research On Environmental Simulation Test Technology And Its Relative Theory Of Concrete Structures

Environmental effects play an important role to the characteristic change of concrete structures while durability and early age property research is involved. Environmental simulation test technology will be studied and used in establishing simulation environment to perform all kinds of simulation research. Accelerated durability test of concrete structures and its relative theory are discussed, as well as shrinkage cracking of concrete at early age with external environment fluctuation. Based on the study, the rules of material damage and deterioration can be achieved to enhance our knowledge on mechanical behavior of concrete. Therefore, the study is of great importance to improve structures safety and durability. The research contents and results are as following:(1) Environmental simulation test technology is studied. The key techniques of environmental test of concrete structures are analyzed. The basic scheme is put forward to construct artificial climatic environmental laboratory with auto control and multifunction. Then, the layout, function and performance of the laboratory is determined suitably.(2) Subsystems of environmental simulation laboratory are detailedly studied, such as main chamber, air cycling, sunlight, raining, adding humidity, dehumidifying, cooling, and heating, and so on. Advanced environmental simulation laboratory can be constructed based on the work.(3) Design methods of environmental test of concrete are discussed. Research models of all kinds of experiments in different environments are listed, which have laid down the basis for environmental tests measuring basic mechanical properties and environmental effects.(4) Strategy for accelerated durability of concrete structures is analyzed. The main contents of accelerated durability study are introduced; design principles of accelerated durability experiment are put forward as well as analysis methods of test data. The basic principles of accelerated durability test are discussed. Service lifespan of concrete structures can be evaluated through accelerated durability tests in laboratory.(5) Autogenous shrinkage of concrete at early age is calculated based on the concept of maturity and degree of hydration. Analytical model of shrinkage due to internal and external drying is established by tests results and humidity diffusion theory. Linear aging viscoelastic constitutive model is used to calculate restrained stress based on the general Maxwell model. Cracking damage criterion can be determined applying strength decreasing factor combined with early age strength development. Shrinkage cracking evaluation of concrete at early age is predicted.