Experimental Study On Influence Of Various Factors On Double-k Fracture Parameters Of RCC

Roller compacted concrete(RCC),a kind of dry heterogeneous hybrid material,has the advantages of low cost and constructing relatively fast.It is accepted rapidly and now used in building roads and dams worldwide.However,with the application of RCC in the field of civil engineering,due to defects of RCC itself and its harsh application environment,some fine cracks are generated inside the RCC so that the applicability and durability of building structures could be weakened.Therefore,the research on the fracture properties of RCC is of great significance for its application in engineering practice.Relying on the National Natural Science Foundation of China project—constrained joint tests and real-time simulation of RCC arch dam considering multiple factors(51479168),In this thesis,made three types of specimens and the wedge splitting test.Analying the independent effects of concrete strength,coarse aggregate particle sizes and specimen sizes on the fracture properties of RCC.Furthermore,the coupling effects of various parameters on the fracture characteristics are reported.Firstly,combined with the calculation method of concrete double K fracture parameters provided by the Hydraulic Concrete Concrete Fracture Test Regulations(DL/T5332-2005),the fracture parameter values of RCC wedged tensile test specimens are calculated.It is found that as the heights of test pieces are more than 300 mm,the values of the fracture toughness of the RCC tend to be basically stable.As the heights of test pieces are less than 300 mm,these values are increased slightly.Under the condition that the seam height ratio of RCC specimens remain unchanged,the bearing capacity and double K fracture parameters of the specimens are increasing with the increase of concrete strength.If the largest coarse aggregate size smaller than 40 mm,the bearing capacity of RCC will increase with the increase of the coarse aggregate sizes,indicating that the coarse aggregate particle size of RCC has a certain inhibitory effect on crack propagation.However,if the largest coarse aggregate size is between 40 mm and 80 mm,the bearing capacity of RCC will decrease with the increase of the coarse aggregate particle size,showing that the aggregate particle size will have a relatively small inhibitory effect on the crack propagation.Finally,based on the study of the independent parameters effected on the fracture properties of RCC,combined with the theory of "equivalent maturity",the relationship between RCC equivalent maturity and fracture parameters under the coupling effects of five parameters,such as temperatures,ages,specimen sizes,concrete strength and coarse aggregate sizes,were studied.The relationship between maturity and double K fracture parameters which is acquired by regression analysis can truly reflect the variation law of fracture parameters and provide a theoretical basis for the study of RCC fracture properties.