The Failure Mechanism Of Crack Sealant Based On The Weak Boundary Layer Theory

At present, crack sealant is an effective, simple and widely maintenance method for repairing cracks in our country. Due to the multiple effects of bad natural environment and complex traffic load, serious early failures occur in the sealant. After a long time of pavement condition survey and indoor experiments, it can be found that the adhesive failure is the most serious type with the proportion exceeds 80%, which reduces the performance and service life of pavement seriously, and wastes a lot of manpower and material resources. Therefore, it is very necessary to explore the failure mechanism of crack sealant. The main content of this paper as follows:According to the laboratory test and field investigation in Northeast of China, it is found that the most serious damage of crack sealant is the adhesive failure. And according to fracture modes of the interface, it is found that the existence of weak boundary layer in the interface is the direct cause of adhesive failure of the crack sealant. This paper presents new text fixture and evaluation method about the low-temperature adhesive performance of the interface between crack sealant and asphalt concrete block based on the existing testing device.The influence of asphalt concrete block which is design to bond with the sealant and the environment on the failure of sealant is analyzed. It is found that void ratio and void size of the bonding surface of concrete block have a direct effect on the sealant failure. And when the temperature is too low and long-term soaking and mixed with sand of crack sealant, the adhesive attraction between sealant and concrete block is affected seriously, and lead to the failure of sealant at last.This paper develops suitable preparation procedures and produces different crack sealants, and analyzes the effect of each component in sealant on the failure. It shows that SBS modifier and rubber powder have an important influence on the failure of crack sealant, and the influence of rubber powder is more serious. When the rubber powder is too big or too much, the component distribution of sealant will change and bring about the weak boundary layer in the interface between sealant and concrete block, and lead to the failure of sealant at last.According to the influence factors of adhesive properties between sealant and concrete block, this paper analyzes the failure mechanism based the weak boundary layer theory and puts forward some effective measures to improve the adhesive properties. These measures include choosing the sealant which performance meets the temperature requirements and reasonable grooving method, coating a layer of waterproof material which has good bonding properties in the surface of sealant, and ensuring has no impurities in the cracks, etc.