Study On Low-temperature Performance Of Pre-sawed Fibers Bituminous Mixtures

Reflection crack is one of the main causes of damage of asphalt pavement in the winter.Under the combined effect of low temperature shrinkage and load,substratum become to crack and the stress concentration caused cracks going up.At the same time,the stress concentration in the cracks is much bigger than no cracks area,which makes the stress easily exceed the limit of the asphalt mixture surface tensile strength and surface crack.Study on low-temperature cracking property and crack propagation behavior of asphalt pavement can provide theoretical basis for surface mixture design;To carry out the study of reflection crack is of great significance to prevent early damage of asphalt mixture surface layer.According to the research results of scholars inland and abroad,this paper summarizes the factors that affect the reflection crack propagation of road surface.We found that incorporation of fiber in asphalt mixture is helpful to improve anti-cracking performance of asphalt mixture.And this paper is aimed to study asphalt mixture mixed with different fibers' low-temperature crack resistance,simulating and predicting incision pre-existing cracks at the bottom of the asphalt pavement surface,and takes research on the expansion of reflective crack in different positions under the load.We design the incision trabecular load three-point bending test using temperature as the influence factor of specimen's low temperature cracking performance,designing test temperature as-10 ? 0 ? and 10?;For the study of fiber in asphalt mixture specimen cracking performance improvements,we compared polyester fiber mixed,basalt fiber mixed,and lignin fiber mixed mixtures with no fibers-mixed mixtures to carry out experiment;For simulation of pavement reflection crack,we set the prefabrication incision which are 10 mm in depth in the bottom of the specimen.And we design incision position offset center distance from the center of the load as:0 mm,20 mm and 40 mm.The results show that the pre-incision trabecular load three point bending test well simulate the characteristics of low temperature cracking and reflection crack behavior of the asphalt mixture pavement;The lower test temperature is,the specimen crack resistance is better;Basalt fiber is stable to improve crack resistance of asphalt mixture;The offset distance between incision and load greater,specimen crack resistance is stronger.It also means that the horizontal distance between reflective crack and the offset load at the center is larger,the specimen crack resistance is stronger.We use ANSYS finite element software to simulate the trabecular's cracking behavior in 10?.By analyzing the test results,analysis of fracture mechanics and results of finite element analysis,we get the crack propagation angle of the calculated value,test results and simulation value,is used to describe crack propagation behavior.Analysis results show that the reflection crack at the bottom of thes pecimen propagation behavior has a certain regularity.According to different location of the crack,crack presents a different angle value range,to measure the crack propagation behavior.When the crack position offset load center distance x = 0,crack angle range is between 0 ° and 3.5°.When x =20m,crack angle range is between 6.9 and 17.5°.When x = 40 mm,the development of crack angle range is between 20 ° to 30 °.