The Preparation And Properties Of Self-healing Materials Of Road

Under the normal usage, the asphalt concrete pavement may have micro cracks anddamages. If these damages are not repaired in time, the minor cracks would extend into muchlarger cracks, which may affect the normal performance and diminish the standard servicelife.This paper introduced the concept of biological self-healing, by adopting of materialsupplement and the use of microcapsule technology to encapsulate and add regenerant agentsinto the asphalt. When the micro-cracks are extended to the microcapsules, the microcapsuleswall will be ruptured and the regeneration agent will improve the properties of asphalt in thecracks and prompt asphalt to achieve good self-healing characteristics at room temperature ora lower temperature. This process will delay the expansion of cracks or even repair cracks,and extend the service life of asphalt pavement.Main contents and conclusion are as following:1. Analyzed the current cons and pros of the microcapsules technology, we confirmedto use situ polymerization for producing microencapsulation, wall material isurea-formaldehyde resins, and the core material of the capsule is permeable asphaltregeneration agent A. This paper explores the regeneration agent microcapsule preparationprocess in detail, and the optimal reaction conditions for microcapsules preparation are:①Formaldehyde molar ratio of1.5:1and urea solution in the alkaline PH of about8ambient,with temperature of60~75℃and60~75min to give the reaction urea formaldehydeprepolymer.②The surfactant used is sodium dodecyl benzene sulfonate, at a concentration of0.5wt%; emulsified stage regeneration speed800r/min.③The emulsified regenerant is addedto the prepolymer solution, controlling the stirring rate at500r/min; capsule core and wallmass ratio of1.2:1. Dilute hydrochloric acid solution was slowly adjusted to PH=3, whileslowly warming to60℃, after the end of the reaction2~3h.④Then stirring was continuedat a slow speed to cool to room temperature. The microcapsules containing the suspensionwas filtered, washed, and dried to obtain microcapsules. Prepared by the structural capabilityof the obtained microcapsules, the microcapsules with good morphology, dense surface, coating was84.94%,82.46%content of the capsule core, the average particle diameter of21.14m, mainly concentrated to5microns between35microns, which is about73.0%of thetotal microcapsule.2. The effect of regeneration agent microcapsule self-healing capacity of asphalt isstudied by the self-healing ductility test and self-healing DSR test. Self-healing ductility testanalysis shows that when the microcapsule content is0.3wt%, the capacity for self-repairasphalt has improved significantly, and does not significantly reduce the bitumen properties.Self-healing DSR test data shows that: When the microcapsules content is0.1wt%, the asphalthas a loading time of1120s in the first fatigue test, which has the strongest resistance tofatigue; and when the content is0.5wt%in the second fatigue test, from loading to destructiontakes449s, anti-fatigue ability was the strongest after healing, means self-healing ability ofthe asphalt is strongest. In conclusion, a small amount of microcapsules will effectivelyincrease the service life of asphalt, but with microcapsule content increases, the overallservice life of the asphalt is reduced but with improving self-healing capacity.