Research On The Asphalt Mixture Crack Test Methods And Evaluation Indexes Based On SCB

Thermal cracking is one of the main failure modes of the asphalt pavement.When the temperature drops down quickly,it will begets the temperature stress inside the asphalt pavement.When the temperature stress exceeds the tensile strength of the asphalt mixture,the asphalt pavement will cracking.The main research field of crack resistance of asphalt concrete in test method and evaluation index of crack resistance.At present,the assessment test of the asphalt mixture property is mainly splitting test,three-point bending test,semi-circular bending test and disk-shaped compact tension test.The stress intensity factor of various specimens is analyzed,and the variation law of stress intensity factor is studied,and the minimum notch depth is determined.Different test methods have their own advantages and disadvantages.By analyzing different test methods,this paper has determined the semi-circular bending test with notch as the method to evaluate the crack resistance of asphalt mixture.The standard fracture energy of the asphalt mixture was calculated by fitting the fracture energy of the specimen with different notch depth,and the reasonableness of the standard fracture energy as the evaluation index of the anti-cracking performance of the asphalt mixture was demonstrated.In this paper,the installation of semi-circular bending test,the forming method and the geometric parameters of the specimen are determined.The specimen's diameter is 150 mm and thickness is 50 mm.The notch depth is 10 mm,20mm and 30 mm respectively.Basis on the research,the semi-circular bending test is carried out,and the failure process of the semi-circular bending test is analyzed.When the temperature is low,the specimen is brittle fracture and the ductile failure is high.During the process of ductile failure,the mixture still has a certain residual strength after the failure is destroyed,and the strength becomes very small after the back bending point of the load curve.The ultimate crack resistance of the asphalt pavement can be evaluated by the fracture energy at the back bending point.Based on the semi-circular bending test,the effects of asphalt properties,gradation,temperature and notch depth on the crack resistance of the mixture were analyzed.The results show that the crack resistance of AC and SMA type asphalt mixture is weak at 15 ?,the standard fracture energy reaches the maximum and the crack resistance is best at 0 ?,the crack resistance is poor at-15 ?.Asphalt properties,gradation,nominal maximum aggregate size is different,will affect the asphalt mixture crack resistance,at different temperatures,the influence is also different.When the temperature is low,such as-15 ?,the asphalt properties,properties of the different has no impact on the standard fracture energy,but the different types of gradients still have a certain impact on the crack resistance of the mixture.The notch depth directly affects the fracture energy of the mixture,the greater the notch depth,the smaller the fracture energy.