Research On Concrete Pore Fractal Characteristic And Its Representation To Chloride Diffusivity

Pore structure of concrete which can affect chloride diffusivity greatly, pore fractal dimension can reflect pore fractal characteristic has fractal characteristic. In this paper, the tested results of imagine analysis and mercury intrusion porosimetry (MIP) have been used to calculate the pore area fractal dimension and pore volume fractal dimension, and the relationship between fractal dimension and chloride diffusivity has also been analysised.On the basis of this research, pore area fractal dimension which changes between 1 and 1.2 is on behalf of the roughness of big pore in concrete, and pore volume fractal dimension which changes between 3 and 3.2 is on behalf of the complex of pore distribution in concrete. With the growth of age, pore area fractal dimension decreases and pore volume fractal dimension increases, and pores filling in concrete become more complicated, as a result chloride diffusivity will decrease when chloride permeate through the pores.When the content of limestone increases from 10% to 30%, pore area fractal dimension of concrete fluctuate at large range, then the correlation between pore area fractal dimension and chloride diffusivity or strength also increases. When different admixtures (such as flyash, slag and limestone) are mixed in with a content of 30%, pore area fractal dimension of them change little, but the chloride diffusivity and strength of concrete change greatly, and the order of the correlation between pore area fractal dimension and them is flyash, slag and limestone, the result indicates the activity of admixture is another important factor we have to consider about.In terms of pore volume fractal dimension, it will fluctuate much when the content of limestone is 10%, and it will decrease as the content increases to 20% or 30%, the order of pore volume fractal dimension fluctuates from high to low is flyash, slag and limestone. The correlation between admixture and chloride diffusivity or strength, summarizes in the end, it has to consider about if this change can let pore volume fractal dimension fluctuates more.In addition, theories have been approached in this paper in combination with Katz-Thompson equation and Byung Hwan Oha equation, model and equation are established between pore structure and chloride diffusivity, and the relationship between fractal dimension and chloride diffusivity can be explained by the model and equation.