Study On Self-healing Properties Of Rubber Asphalt Mixture With Microcapsules

Micro cracks will inevitably occur during the normal use of asphalt pavement.If it cannot be repaired in time,the micro cracks will gradually expand into macro cracks,affecting the normal service performance and service life of the asphalt pavement.The rubber asphalt pavement has good road performance,especially low temperature crack resistance.It can effectively improve the cracking problem of asphalt pavement.Meanwhile,micro capsules self healing technology can make materials self-repair by encapsulating the healing agent.When the micro cracks extend to the micro capsules,the micro capsules will be punctured due to the stress concentration at the tip of the micro cracks.At this time,the healing agent can flow out and promote micro-cracks to heal spontaneously at natural temperatures,extending the service life of the asphalt pavement.In this paper,the toughening technology of rubber asphalt mixture and micro capsules self-healing repair technology are combined to give full play to their technical advantages.At the same time,the author has studied the synthesis of micro capsules,the performance of micro capsules,the self-healing properties of rubber asphalt mixtures containing micro capsules,and road performance.The main tasks include the following aspects:First,a large number of domestic and foreign literatures were referenced to analyze the synthesis methods of various micro capsules.According to the existing experimental conditions,the orifice-coagulation bath method was selected as the synthesis method of the micro capsules,and calcium alginate was used as the wall material.Seed oil as a core material.In order to select the micro capsules that can be used in rubber bitumen mixture,six oil-water ratios of calcium alginate micro capsules,which are 1:1,1:2,1:4,1:6,1:8 and 1;10,are prepared by the same synthetic process.It is found that with the decrease of oil/water ratio,the encapsulation and encapsulation efficiency of micro capsules are better and the mechanical properties are also enhanced.Therefore,from the internal and external structure,heat resistance and pressure resistance of micro capsules,this paper focuses on the micro capsules with better encapsulation performance which oil/water ratio is 1:6,1:8,1:10.The results of the study indicate that the micro capsules with oil/water ratio 1:10 are optimal in all three respects.Therefore,this micro capsule was selected as the final test micro capsule.Secondly,considering the addition of micro capsules and the design method of rubber asphalt mixture,the optimum oil stone ratio of the rubber asphalt mixture with micro capsules was determined by the Marshall test.By analyzing the self-healing property evaluation method of the existing asphalt mixture,the four-point bending fatigue test is considered as the best evaluation method for the self-healing properties of rubber asphalt mixture with micro capsules.The authors selected four-point bending fatigue test to give a 20h interval between rubber asphalt mixture with micro capsules and rubber asphalt mixture without micro capsules.The results show that the rubber asphalt mixture has a certain self-healing ability;the incorporation of the micro capsules reduces the mechanical properties of the rubber asphalt mixture,but prolongs its fatigue life;the calcium alginate micro capsule with a 1:10 oil-water ratio can enhance Self-healing properties of rubber asphalt mixture.Finally,in the condition of the best ratio of oil and stone,combined with the rutting test,low-temperature trabecular test,water-soaked Marshall test and freeze-thaw chapping test,this paper studies the road performance of rubber asphalt mixture mixed with micro capsules.It was found that the presence of the micro capsules reduced the road performance of the rubber asphalt mixture,but still met the requirements for use,in which the reduction in high temperature stability performance was most pronounced.Therefore,it is suggested that the properties of the rubber asphalt mixture with micro capsules should be further optimized from the dimension design of micro capsule,the design of internal and external structure and the mixture ratio of mixture.