Study On Long Term Performance Of Cement Stabilized Old Pavement Aggregate

Recycling the old asphalt mixture and old concrete aggregate as the old material applied to the road base,not only can reduce the impact of the stacking and burying of the old material on the environment,but also can turn waste into treasure,reuse resources,respond to the national environmental protection and green construction concept.At present,there are many achievements in the short-term performance research of cement stabilized recycled aggregate and old asphalt mixture,such as compressive strength,temperature shrinkage and dry shrinkage.The research on the long-term performance of water stabilized old asphalt mixture and old concrete aggregate used in road base is insufficient,which affects the further promotion and use of these recycled materials.The main contents include:(1)The physical and mechanical properties of recycled aggregate and old asphalt mixture are tested,and the differences of aggregate properties and its internal components are analyzed(2)The influence of recycled old material content,cement dosage and curing age on ultimate flexural strength and fatigue resistance is explored(3)The effects of recycled materials and cement dosage on the mass loss and compressive strength loss of the specimens after five freeze-thaw cycles were studied(4)Using the self built scouring test equipment with high convenience and accuracy,taking the mass loss of test specimen and unconfined compressive strength loss as evaluation indexes,the influence of old material content and cement dosage on anti scouring performance is explored;Explore the method of mixture gradation optimization to effectively improve the anti scouring performance(5)Comparative analysis and Research on the data of plant mixture and laboratory in engineering test section.The main conclusions are as follows:(1)With the increase of the content of old materials,the strength loss of the specimen increases gradually,and the freezing stability coefficient decreases,and the decreasing speed increases gradually;With the increase of cement dosage,the frost stability coefficient is improved(2)With the increase of recycled aggregate and old asphalt mixture content,the ultimate flexural strength and fatigue life first increase slightly and then decrease significantly,and there is an obvious inflection point.The results show that the mixture with recycled aggregate content less than 35% and recycled old asphalt content less than 30% has the best anti fatigue performance;The flexural tensile strength and flexural fatigue performance can be significantly improved by increasing the cement dosage,and the best performance can be obtained when the cement dosage is about 4%-5%(3)With the increase of recycled aggregate and old asphalt mixture,the erosion resistance of cement stabilized base decreases significantly;With the increase of cement dosage,the cumulative erosion amount and compressive strength loss of the specimens decrease,which significantly improves the anti erosion performance.It is reasonable to use about 4%cement dosage(4)Compared with the original gradation,the improved gradation can reduce the mass and unconfined compressive strength loss of specimens after scouring test to a certain extent,and then improve the anti scouring ability of road base mixture.On the premise of meeting the grading requirements,recycled fine aggregate should not be used as much as possible,and natural fine aggregate should be used as little as possible.