| The current asphalt concrete pavement has entered the period of maintenance.There are about 19 million tons of RAP generated every year,and this number is still growing now.Therefore,it is urgent to increase the utilization rate of RAP to reduce the waste of resources and environmental pollution.After decades of research by road workers on pavement regeneration technology,the current research on hot mix asphalt regeneration technology and warm mix asphalt regeneration technology is mature.The former has a good effect on the recovery of asphalt performance,but the mixing temperature is too high during the construction process,which leads to excessive energy consumption and pollution;while the latter achieves a lower mixing temperature,but the improvement of the performance of aging asphalt by warm mixing agent is weak.And the utilization rate of waste and RAP is not high,it needs to be reconciled through the reconciliation of RAP and new asphalt.Existing studies have little effect on the performance and mechanism of asphalt under the combined action of regenerant and warm mix additives.This article systematically studies the macroscopic performance,rheological properties,composition changes,colloidal structure and microstructure of the warm-mixed recycled asphalt binder.To this end,it carried out the following research efforts:(1)Determine the dosage of regenerant.The best dosage of regenerant was determined through conventional indexes and rheological performance indexes such as three indexes?DSR temperature scanning.Then add the warm mix additives to the prepared recycled asphalt binder,to investigate whether the performance of the reclaimed asphalt will change after the warm mix additives and regenerant are added at the same time.Through the Rotational Viscosity Test to explore the viscosity reducing effect of the warm mix additives.The test results prove that the asphalt mixture has good performance under the combined action of warm mix additives and regenerant.(2)DSR temperature sweep,frequency sweep and LAS amplitude sweep experiments were carried out on the asphalt binder to analyze the high and low temperature performance,visco-elastic properties and fatigue resistance of asphalt.The results show that the regenerant can effectively reduce the complex shear modulus,increase the phase angle,and improve the visco-elastic component ratio of the asphalt binder.The addition of the warm mix additives makes the change of these two indicators more complicated.Under the combined action of regenerant and warm mix additives,it will reduce the ability of asphalt binder to resist repeated load,but improve the elasticity of asphalt binder and increase its fatigue life.(3)Through the four-component separation test of asphalt binder,determine the changes of asphalt components and colloidal structure during the aging and regeneration process.Thetest results prove that the components of warm-mixed asphalt and hot-recycled asphalt have the same change trend,and the warm mix additives will not change the four-component ratio of asphalt binders.By calculating the difference between the theoretical value and the actual value after regeneration,the mechanism of action of the regenerant is judged,and it is concluded that each component in regeneration is not a simple superposition of the physical layer,but a chemical component migration has occurred.The connection of macroscopic properties proves that asphaltene and colloid have a greater influence on the high temperature index of asphalt,while aromatics and saturated components mainly affect the low temperature index of asphalt.(4)Fourier infrared spectroscopy test was used to qualitatively and quantitatively analyze the functional group index of the two recycled asphalts,and through differential scanning calorimetry test to study the thermal properties of asphalt,such as glass transition temperature,endothermic peak characteristic parameters,it provides theoretical support for the study of asphalt aging and regeneration mechanisms at the micro level. |
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