Mesoscopic Numerical Simulation Of Chloride Ion Permeability In High Performance Concrete

Owing to the high strength,high workability and high durability,high performance concrete,widely accepted in all areas of national production in recent years,is one of the most important new building materials with vast development foreground.As for the main corrosion way of high performance concrete under marine environment,chloride corrosion attract lots of attention of scholars on deeper research.Overall,research on high performance concrete is still in early stage,and there is few research about chloride ion penetration from the meso-level.Concrete could be regarded as a three-phase composites material consisted of mortar,aggregates and transition layers from the the meso-level.The concrete has complex meso-structure and its permeability or transmission affected by synergy effects of many factors.Test methods are difficult to determine the separate effects of factors.From the microscopic point of view,effects of each factor on chloride ion ingress in high performance concrete is take into account respectively,and is numerically simulated through MATLAB and COMSOL.The specific works are as follows:(1)Through the review of related literature at home and abroad,the transmission mechanisms of chloride ion in high performance concrete are summarized to lay a theoretical foundation for subsequent establishment of micro-model and analysis.(2)A group of high performance concrete specimens was fabricated according to regulatory requirements,and naturally immersion method was selected for chloride corrosion test for high performance concrete.The chloride ion transmission in ordinary concrete and high performance concrete were compared and analyzed,and effect of concrete strength on chloride ion transmission in high performance concrete was analyzed.(3)On the basis of random numbers by Monte Carlo method,the two-dimensional circular random aggregate model was established by Matlab program,and a polygon based aggregates was randomly generated within the random circle,which made the area of the polygon become 0.75-1.1 times greater than or equal to the random area of the circle.Finally,based on the longest side edges as the reference edge,new points were generated and judged whether meet the rules for extending outward conditions,and two-dimensional random aggregate model of a polygon was eatablished.(4)Concrete was regarded as a three-phase composites material consisted of mortar,aggregates and transition layers.The two-dimensional random aggregate model was meshing by COMSOL to establish the finite element model of two-dimensional random aggregate.On basis of this,effect of aggregate,mineral admixture and relative humidity and temperature and other factors on chloride ion transmission were numerically simulated and analyzed.