Thermo-hygro-mechanical Model Of Early-age Concrete Based On Micro-pore Structure Evolution

With the proceeding of hydration, the microstructure of concrete at early age evolves continually. Meanwhile temperature and humidity in the concrete change vehemently, which significantly influences the developing of the mechanical properties of concrete. Studying the coupling thermo-hygro-mechanical relationship and the correlation among temperature, humidity and mechanical property of early-age concrete are of great importance for understanding the macroscopic mechanical properties of concrete, which are also meaningful for preventing deformation and cracking of early-age concrete. The main research work of this thesis is as follow:(1) To establish the coupling thermo-hygro model based on hybrid mixture theory (HMT) considering the characteristic of the microstructure evolution of early-age concrete. The adsorption curve of early-age concrete is acquired based on the microstructure evolution through establishing the relationship between saturation and several factors, such as hydration degree, temperature, capillary pressure and so on. An innovative coefficient for counting the influence of humidity on hydration rate is proposed, which takes the influence of humidity on hydration rate under self-desiccation as a reference based on the existing test.(2) The test for measuring the temperature and humidity at different location of early-age concrete is conducted under different environment including constant and cyclic temperature and humidity. The degree of coupling relationship between temperature and humidity is analyzed specifically. The experiment results agree well with the model prediction results. And the further influence of coupling thermo-hygro relation on the proceeding of hydration is explored based on the validated test, which revises the theory model continually.(3) To establish the coupling thermo-hygro-mechanical model based on the microstructure evolution of early-age concrete. The deformation of concrete under external load can cause water redistribution in the concrete pores, which may induce the variation of the internal relative humidity. This thesis takes the effect of the deformation of solid phase on thermo-hygro transfer into account based on the coupling thermo-hygro model of early-age concrete. The influence of the loading on the porosity and the intrinsic permeability coefficient of early-age concrete is deduced. Finally the effect of loading on the temperature and relative humidity is analyzed emphatically by means of concrete axial compression.