Research On The Double-K Fracture Parameter Of Multi-factor Roller Compacted Concrete

Roller compacted concrete is a kind of bigger consistency of mixture and need to be vibrated compaction super hard dry concrete,it has the advantages of rapid construction,save the dosage of cement and reduce the mass concrete temperature rise,etc.With the construction of the roller compacted concrete dam around world in a short time,during the dam operation,the defects of concrete and the change of the environment lead to both internal and surface cracks,it will result in the crack of the Roller compacted concrete dam,and then,it will affect the durability and application of the dam.So the fracture mechanism of roller compacted concrete has important realistic significance and practical engineering value.This paper from the roller compacted concrete three aspects of the initial crack-depth ratio,age and curing temperature to analyze the influences of various factors on the fracture behavior,and provide effective theoretical foundation for the study of roller compacted concrete anti-cracking.In this paper,through many different groups of the initial crack-depth ratio,age and the curing temperature of wedge splitting RCC specimens complete fracture tests was carried out.Based on the double K fracture theory and according to norm for fracture test of hydraulic concrete,double K fracture parameters calculation formula to calculate double K fracture parameters value of roller compacted concrete wedge splitting specimen is calculated.By analyzing the test data,some concluding are shown as followed:(1)Under the same size,the smaller the initial length,the longer the critical crack propagated length and the larged the toughness,along with the increase of crack-depth ratio,the degree of crack propagation almost invar,in the condition of different crack-depth ratio,the crack fracture toughness value change very small,it can be considered to be material intrinsic parameters,with the increase of crack-depth ratio,unstable fracture toughness increase firstly and then steady;(2)Roller compacted concrete initial load and unstable load increase with the increase of the age,the ratio of crack load and unstable load is between 0.4405 and 0.5835.Along with the increase of age,the crack load,the greater the proportion of buckling load.The critical effective crack length and the critical crack propagated length declined with the increase of age,it is showed that the longer the age,the worse the ductility of the specimen,the more to probability brittle failure.The change rule of normal concrete fracture parameters affected by age is same as RCC.Whether through specific age under corresponding to the ordinary concrete fracture parameters calculated values of fracture parameters of RCC under age remains to be studied;(3)In the different temperatures,roller compacted concrete wedge splitting specimens the crack fracture toughness and the unstable fracture toughness ratio of tends to be stable,and the fracture toughness and crack instability fracture toughness increases with temperature;(4)To determine the equivalent temperature of roller compacted concrete dam fracture parameters and the equivalent relation between maturity and effectively reflect the fracture parameters of RCC dam with temperature and ages of the law of development,in order to further improve the formula to solve the problem of the size effect of fracture parameters.