Pore Fractal Characteristics Of Cement-based Materials And Carbonation Behavior

This paper aims to use fractal theory to analysis the pore structure characteristics ofconcrete. Through researching on the chaos and fractals theory, establish the fractal theoryrelated to high performance, high function concrete, especially establish the theory related toconcrete durability to provide a theoretical basis for the engineering application. In order torealize the goal of concrete materials science and technology, try our best to manufacture thehigh performance, high function concrete in the specified performance design.Cement-based materials are composite systems which have a complex structure ofheterogeneity, multiphase (gas, liquid and solid) and multi-level (microscopic,submicroscopicand macroscopic). Its macroscopic physical mechanics behavior showed irregularity, uncertaintyand fuzziness, nonlinearity, etc. Those reflect the complexity of microstructure. Thecharacteristics of macro gather some structure and micro porous structure and the mechanicalbehavior and durability are connected closely. The complexity,the particularity in macroscopicand microscopic structure,the universality of use parts of the constituent materials, whichdetermine the concrete materials science had to depend on the latest research results of variousdisciplines of cross to improve their own. Concrete materials fractal theory can be used to be anew branch of materials scientific researching, as following the materials science,micromechanics, fracture mechanics, cement chemistry, rheological etc. It is very effective thatanalyse and evaluate on series of characteristics of concrete material, research materialcomposition, structure and failure mechanism, describe microscopic fine structure andmicroscopic levels of the mechanical behavior and the macro field performance self-similarityfeatures by using fractal scientific.In order to research on the change rule on fractal characteristics of the pore of cement basedmaterials further. Under the guidance of the fractal theory, explore the fractal characteristics ofpore structure that is related to surface area of the pore of the cement base composite materialswith various admixtures and different mix proportion by nitrogen adsorption method. Based onthe fractal theory, using the mercury injection pore method (MIP) study the fractal characteristicsof pore structure of different admixtures of concrete material. Using fractal theory can explainthe change of pore structure quantitatively, explore the relationship between concrete carbonationand the quantitative characteristics of pore micro structure, research on the change of porestructure influence on carbonization durability. Research shows that, surface area of the complexinternal structure of cement based materials has the fractal characteristics observably. Testing andevaluating the fractal characteristics on surface area of the pore of cement-based materials bynitrogen adsorption method is effective. The fractal dimension of pore surface area is between 2.36and2.58. It is good for analyzing surface characteristics of pore structure further. Surfacefractal dimension of pore structure and surface area have not good correlation, correlationcoefficient is-0.636. This characteristics and conclusion that quality fractal dimension of powderand surface area evaluating fineness of powder have not very good correlation is consistent.Surface fractal dimension of pore structure and strength have not good correlation, correlationcoefficient is-0.393. But Surface fractal dimension of pore structure and volume have goodcorrelation, correlation coefficient is-0.812.The pore structure of concrete has the remarkable multiple fractal characteristics. Usingfractal theory can explain the change of pore structure quantitatively, establish the quantitativemodel among pore fractal dimension, age and carbonation depth. Variance analysis shows thatthe model among pore fractal dimension, age and carbonation depth is remarkable. It is provedthat, the carbonization durability studied by pore fractal characteristics is effective. It provides anew method for evaluating the carbonization durability of concrete structure durabilityreasonably. With changing thick depending on the drawing method, can fine measure thecarbonation depth of concrete.