| Because of the high utilization rate of obsolete asphalt pavement materials,low energy consumption and low pollution,the emulsified asphalt central plant cold recycling technology has shown good road performance in the maintenance and expansion projects of various levels of pavement,and the economic and environmental benefits are pretty high.However,due to the complicated geomorphology and climatic conditions,the application and promotion of emulsified asphalt central plant cold recycling technology in the mountainous areas of western Sichuan is insufficient.In view of this,this paper has carried out relevant researches on the optimized method of mix design,road performance,curing method in the normal temperature and humid environment and the secondary hot compaction characteristics of cold recycled asphalt emulsified mixture(EACRM).The construction process has been ameliorated by paving a test road,and the relevant conclusions of the indoor tests have been verified.The main research work and conclusions of this paper are as follows:(1)The design method of EACRM is optimized,mainly reflected in these points: the EACRM gradation design method after reclaimed asphalt pavement(RAP)extraction is proposed;the feasibility of Marshall compaction method for determining the optimal moisture content is verified;the Core Lok is adopted to ameliorate the void content determination method;and the test steps of the optimal emulsified asphalt content and the optimal cement content are separated.(2)Through the preliminary tests,the relevant parameters of road performances tests were determined and revised,and the designed mix is tested.Through the orthogonal test method,the sensitivity and significance of EACRM’s road performances are studied.It is found that the high curing temperature significantly affects the strength and anti-stripping performance;the cement content affects the high temperature stability,low-temperature crack resistance and water stability performance significantly;and RAP content affects the fatigue performance significantly.The optimal gradation is determined,and the optimal cement content is adjusted on the basis of the sensitivity and significance of road performances.And it has been found that,the best cement content obtained by using dry-wet split ratio as a control index,which can not make EACRM achieve the optimal road performances.(3)For the main controlling factors of EACRM’s road performances,a single factor analysis is carried out.It shows that,with the increase of the amount of emulsified asphalt and the amount of RAP,the high temperature stability of EACRM gradually declines,the fatigue performance gradually enhances,and the water stability first enhances and then declines.And with the increase of cement content,the high temperature stability gradually enhances,the low-temperature crack resistance and fatigue performance first enhance and then decline,and the water stability gradually enhances.Compared with P.C42.5 cement,P.O42.5 cement strengthens the high temperature stability and water stability more significantly,but the lowtemperature crack resistance and fatigue performance are worse.When the amount of emulsified asphalt is greater than 3.5%,EACRM can meet the low-temperature crack resistance requirements of ordinary asphalt mixture,and when the RAP content is 88%,the low-temperature crack resistance and water stability of EACRM is best,which further verifies the optimal gradation,and the optimal amount of emulsified asphalt is adjusted to obtain the production mix.(4)The normal temperature and humid environment is simulated by indoor tests to study the control methods and performances changes of EACRM in this condition.In the normal temperature and humid environment,EACRM can end curing at 15°C for 10 days,20°C for 7days,and 25°C for 4 days.When the temperature is lower than 15°C,it is not suitable for construction of EACRM.And the strength of EACRM increases slowly,the low-temperature crack resistance gradually declines.In the projects,care should be taken to prevent the lowtemperature cracking of EACRM layer caused by the sudden drop in temperature after being in the normal temperature and humid environment for a long time.(5)Marshall secondary compaction,secondary roller rolling and the secondary shear gyratory compaction(SGC)tests are used to simulate the EACRM secondary hot compaction process,and the characteristics of secondary hot compaction and road performances increse extent were studied quantitatively.It is found that,when the number of Marshall’s first compaction exceeds 50 times and the number of the secondary compaction exceeds 25 times,EACRM is difficult to continue to be compacted.After the secondary hot compaction of EACRM,the degree of compaction is further strengthened,but if emulsified asphalt cold recycled layer is thick enough,there will be a gap between the bottom and the upper part of the layer after the secondary hot compaction.EACRM is more difficult to be compacted to the specified degree of compaction than SBS AC-13 C,and the ability to resist deformation is worse.The lower layer EACRM and the upper layer SBS AC-13 C have the same compaction effect by Marshall double-sided compaction 35+25 times,wheel rolling 24+36 times,and SGC compaction 65+100 times,or Marshall double-sided compaction 50+25 times,wheel rolling32+36 times,SGC compaction 100+100 times.In terms of road performances of EACRM after the secondary hot compaction,the high temperature stability can be strengthened by more than 30%.The secondary hot compaction greatly increases the low-temperature bending flexural tensile strength,thereby significantly strengthen the low-temperature crack resistance,and when the bending strain energy density is used to characterize the low-temperature crack resistance,the low-temperature crack resistance performance of EACRM is increased by more than 20%.After the secondary hot compaction,fatigue life of 200με strain level is increased by more than 70%.And the water stability performance is also greatly strengthened.The stability of various road performances is better than before the secondary hot compaction.(6)By paving an emulsified asphalt central plant cold recycling test road,the construction technology are ameliorated,and the relevant indoor tests conclusions are verified.It has established a successful engineering example for the further promotion of amulsified asphalt central plant cold recycling technology in mountainous areas of western Sichuan. |
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