Research On Microstructure Of Warm Mix Asphalt Based On Traditional Compaction Methods

At present, the asphalt pavement in road construction mostly adopts the traditionalmaterial HMA(Hot Mix Asphalt), It is the asphalt heated from room temperature to about140℃, the mineral aggregate heated from room temperature to160℃~180℃, and thenmixing asphalt with mineral aggregate in a high temperature of160℃, dischargetemperature no less than150℃, the temperature of paving and rolling is not lower than120℃.However the usage of HMA can causes environmental damage, excessiveconsumption of energy and shrink of living space for people. In order to protect theenvironment, save energy, warm mix asphalt (WMA) is a new product applications as agreen energy saving and environmental protection.WMA is a kind of mix asphalttechnology which can force it to be mixed and construction in the temperature betweenHMA and CMA with the help of certain techniques or additives. Meanwhile， Itsperformance is comparable to HMA.This paper studied lab compaction test of warm mix asphalt, the gradation type isAC-13F and the mixing temperature is130℃, the same gradation of base asphalt mixturemixing temperature is155℃. First, Through the Marshall compaction tests and gyratorycompaction tests, compaction characteristics of warm mix asphalt under differentcompaction methods were studied, the impact that compacting method and compactiontimes and vertical pressure have on volumetric property of warm mix asphalt were analyzedand compared with base asphalt mixture, determined the best test parameters of warm mixasphalt with lab test. Then, with the help of gyratory compaction densification curve tounderstand the data about the accurate change of warm mix asphalt in height during thecompaction in the lab, and the densification curve of test are derived；Finally, processing theinternal section diagram of the asphalt mixture specimen with the help of digital imageprocessing technology, research to internal voids distribution of warm mix asphalt in different molding methods, seek the internal relations between volume properties andcompaction modeof warm mix asphalt.In the marsh design method compaction times75Times, warm mix asphalt to reach thesame porosity with hot asphalt mixture, compaction number to increase25Times, that is tosay, the best compaction times is95Times with the Marshall test; the best compaction timesis50Times and vertical pressure is600kPa with the gyratory compaction tests; the Marshalltest is more sensitive to the gyratory compaction tests on temperature; improving gyratorycompaction densification curve studied the compaction performance of asphalt mixture, getthe construction Energy Index of warm mix asphalt is lower than that of base asphalt mixtureand Traffic Densification Index is higher than it，It shows that warm mix asphalt are easy tobe compacted and good deformation resistance ability, Gyratory compaction tests arecommendably adapted to reflect compaction performance of Evotherm DAT warm asphaltmixture;Digital image processing technique is adopted to study air void characteristic parameters of asphalt mixtures (air void area, air void diameter, air void perimeter) and air void distribution characteristic parameters (air void quantity, air void percentage,air void fractaldimension, average equivalent diameter of air void). The paper makesprimary research on air voids distribution in warm mix asphalt with different compaction methods and the complexity of the voids distribution, proves that there are also non-uniformity infine structure of warm mix asphalt.