Multi-scale Study On Mechanical Properties Of Concrete Exposed To Acidic Solution

Microstructures,contents of all elements and porosity of concrete will change because of acid rain corrosion,which will heavily influence the mechanical properties of concrete materials and reduce the life of concrete materials.Relevant achievements of mechanical tests and numerical simulations of concrete corroded were concluded with home and abroad, and the properties of concrete corroded were studied by experiments and numerical simulations from several aspects which include macro、mesoscopic and micro.These are supported by the National Natural Science Foundation named the study of Carrying capacity of reinforced concrete bridge in corrosion and load.The main contents include:1.The analysis of the concrete microstructure in acid rain.One hundred groups of concrete specimens which are10mm×10mm×10mm are used.Mixed solutions of sulfuric acid nitric acid which include pH1.0、pH1.5and pH2.5are adopted to corrode the specimens.Variations of micro-porosities、microstructures and relative element contents are received by MIP、SEM and EDS.2.The analysis of the concrete mesostructure in acid rain.Using concrete specimens of150mm×150mm×150mm,it were scanned at different times during corrosion by CT. Image segmentation and digital processions of concrete sectional drawings are accomplished with MATLAB,recognizing the aggregate-mortar spatial distributions and studying the variations of the porosities of concrete with time dependent in different corrosions.3.The spatial distribution of aggregates、mortar and pores are received,and the two dimension geometric model of concrete has been built by dividing the images and monitoring the edges of concrete.The mesoscopic stress-strain relation has been given and regulated depending on different corrosive conditions.The two-dimensional numerical model of concrete has been built.4.The two-dimensional numerical simulations of uniaxial compressing and pulling concrete has been done,researching the variations of stress-strain relationship which depends on the percent of loads、geometries and the degree of corrosion,analysing the unhomogeneous dispersions of stresses around the pores,discussing the damage rules and the developing trends of cracks of corroded concrete,rebuilding the three-dimension numerical model of concrete in order to offer the basements for numerical simulating in three-dimension.