The Fractal Characteristics’ Study Of Waste Fiber Recycled Concrete

With the rapid development of the national economy in recent years, a large number of waste concrete have been produced in the process of building and removing buildings, which has caused huge economic burden to the country and caused serious pollution to the natural environment at the same time. As a kind of new green concrete for recycling of waste concrete and waste fibers,the research of waste fiber recycled concrete has gradually attracted the attention of the whole society.The macro physical and mechanical behavior of concrete materials is characterized by irregularity, uncertainty, fuzziness and self s imilarity, and it is the comprehensive expression of the complexity of its microstructure. This paper based on fractal theory to research the fractal characteristics of pore structure of waste fiber recycled concrete were studied, and the pore structure of recycled concrete was studied by using mercury injection test.A variety of fractal model of concrete internal structure is introduced in detail. Pore structure characteristic parameters of waste fiber recycled concrete were obtained by mercury injection test, then analyze the pore structure characteristics of concrete with different water cement ratio, different recycled aggregate, different fiber length and fiber content, use fractal theory to explain the complexity of the internal structure of waste fiber recycled concrete from the microscopic mechanism. The research shows that, The internal pore structure of waste fiber recycled concrete has obvious fractal characteristics; using fractal theory to analyze and evaluate the internal pore structure of waste fiber recycled concrete is effective, the fractal dimension of pore volume is from 2.64 to 2.73, there is a good correlation between the fractal dimension of pore volume and other parameters.Through the strength and durability test of waste fiber recycled concrete, the relationship between the concrete pore structure and macro properties was established, and the essence of the macro physical phenomenon of waste fiber recycled concrete was revealed by using the fractal dimension of pore volume. Using the method of changing the degree of rough degree to measure the depth of carbonation of recycled concrete, and calculate the fractal dimension of the boundary contour of the waste fiber. The research shows that, there is a certain relation betwee n the fractal dimension and the macro mechanical properties of waste fiber recycled concrete, the compressive strength and splitting tensile strength can be reflected in a certain extent; with the increase of the fractal dimension of pore volume, the compressive strength and the splitting tensile strength increase. There is a certain relation between the fractal dimension and the durability of waste fiber recycled concrete, it can reflect the size of the air permeability, air penetration depth and depth of carbonation in a certain extent; with the increase of the fractal dimension of pore volume, the air permeability, air permeability and carbonation depth decrease.