| With the increase of highway mileage in our country year by year,the task of highway repairment and maintenance is becoming more and more serious.A large number of RAP materials produced in the process of highway repairment and maintenance not only occupy land space resources,but also bring pollution to the environment.The emergence of these problems makes people pay more attention to RAP regeneration technology.At present,the recycling of RAP at home and abroad is mostly controlled within the dosage of 30%,but there is lack of corresponding experimental study on the higher content of RAP.For this reason,this paper combines the material characteristics of GA and RAP to develop RGA?Regenerated Guss Asphalt?with higher content?>50%?of RAP.The influence of different parameters on its performance is analyzed,and the performances of RGA and GA in various aspects are comprehensively evaluated,then,RGA is also applied in practical engineering.Firstly,the performance indexes of raw materials were tested,and the old asphalt in RAP was separated from aggregate by extraction and screening test,and the properties of old asphalt,aggregate gradation and mechanical properties were tested respectively.Then,based on the aging,regeneration mechanism of asphalt and the strength formation mechanism of GA,the regeneration concept of RGA was put forward and the mix proportion was designed to determine the primary selection of RGA.The primary ratio of RGA was determined to be 76:24 and the filler-bitumen ratio of new material was 5.0.Secondly,the effects of different production control parameters?RAP heating time,RAP heating temperature,mixing temperature,mixing time?and mix proportion design parameters?filler-bitumen ratio,RAP content?on the performance of RGA were studied by fluidity test,penetration test and low temperature bending test.The experimental results show that all parameters have significant influence on the performance of RGA.For production control parameters,the increase of RAP heating time,RAP heating temperature and mixing time will lead to the decrease of RGA penetration,penetration increment and low-temperature flexural-tensile strain but the increase of fluidity;while the increase of mixing temperature is beneficial to the fusion of new and old asphalt on RGA,so it will lead to the increase of RGA penetration and penetration increment,but the fluidity and low-temperature flexural-tensile strain will decrease with the increase of the strain.For mix design parameters,the increase of filler-bitumen ratio will make RGA fluidity show an obvious upward trend,while penetration and low-temperature flexural-tensile strain show a significant downward trend.Since the best filler-bitumen ratio of RGA is based on three indicators,the performance indicators of RGA do not show a single change trend with the increase of RAP content.According to the performance of RGA under various parameters,the heating temperature of RAP,heating time of RAP,mixing temperature and mixing time were determined respectively to be150?,60min,230?and 45min.Under these parameters,the optimum RAP content and filler-bitumen ratio for RGA production were 78%and 4.8.Thirdly,a group of GA gradation was formed on the premise that the pass rate of the key sieve hole?0.075mm?is the same as that of RGA and the pass rate of other sieve holes is approximately close to each other.The optimal oil-stone ratio corresponding to the gradation is selected and GA is formed.The high-temperature,low-temperature,fatigue and mechanical performance of RGA and GA are tested and evaluated comprehensively.The experimental results show that the high-temperature performance of RGA at different temperatures are all lower than those of GA,but its penetration?3.34mm?and penetration increment?0.28mm?of RGA can satisfy the requirements of specifications at 60?.For the low-temperature performance,the bending strain of RGA at different temperatures is slightly lower than that of GA,and is higher than that of the specification at-10?by 2.5×10-3.In addition,the shear strength parameters,cohesion“c”and internal friction angle“?”,of RGA are slightly lower than that of GA,and the shear strength of RGA is only 17.18kPa lower than GA.In terms of fatigue performance,the fatigue life of RGA at various strain levels can only reach more than23%of GA,although its fatigue performance is lower than that of GA,but much higher than that of AC,SMA and other conventional hot recycled materials.Therefore,based on the comprehensive performance of RGA,it is considered that it can meet the requirements of practical engineering application.Finally,the test section of RGA is paved with the determined production control parameters and mix proportion.The construction technology of RGA applied in repair engineering are described,and the implementation effect is evaluated and tracked.The results show that all the performance indexes of RGA can meet the requirements of the specifications,and the test sections perform well without disease. |
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