| As an efficient,economical and environmental-friendly maintenance process for the repair of asphalt concrete pavement diseases,hot in-place recycling has always attracted much attention.Among them,the pavement heating technology is the core of the asphalt pavement hot in-place recycling maintenance process.Infrared radiation heating has become the mainstream asphalt pavement heating technology in the market due to its high heating efficiency and strong penetration ability.However,the selection of the infrared bands of the infrared radiation emitted by the metal fiber mesh in the infrared radiant heater is based on simple theories and experience at present,and there is a lack of in-depth analysis and demonstration.Therefore,in order to determine the optimal band of infrared radiant heating for hot in-place recycling of asphalt pavement and achieve efficient and economic heating goals,it is necessary to study heating effect and law of infrared radiant heaters on asphalt pavements at different infrared wavelengths.Firstly,this article analyzed the infrared spectrum absorption characteristics of the three main components of the asphalt mixture: SBS modified asphalt,coarse and fine aggregate(stone)and water,and determined the absorption peak in the wavelength range of 2-15μm.Secondly,the study determined the heat energy transmission efficiency of the whole process of in-place heating of the asphalt pavement with gas infrared radiation,including the heat energy transmission efficiency of the metal fiber mesh surface and the heat energy transmission efficiency of the heater to the asphalt pavement,which provided the calculation of the energy consumption of the heater at different wavelengths with theoretical basis.Thirdly,on the basis of the two theories of infrared “matching” absorption and “non-matching(or partial matching)” absorption,considering the combustion characteristics and material characteristics of the metal fiber mesh,it was determined that the wavelength band of the infrared radiant heater simulation demonstration was 2.5-6μm.Finally,ABAQUS finite element analysis software was used to establish a physical model of the semi-rigid asphalt pavement with AK-16 as the upper layer and AC-20 as the middle layer.The simulation showed that the heating time and energy consumption data of the asphalt pavement by the heater at different wavelengths in the 2.5-6μm band were obtained.The data analysis results showed: in the infrared band of 2.5-6μm,with the increase of the wavelength,the heating time of the infrared radiant heater of the AK-16 graded asphalt pavement firstly increased slowly,and then sharply increased;the consumption of energy of the infrared radiant heater was firstly reduced rapidly,and then slowly reduced.After comprehensive analysis of two evaluation indicators of heating time and energy consumption,the band 4.0-5.0μm was selected as the best band for the hot in-place recycling of asphalt pavement infrared radiation heating when heating distance was 10 cm,the corresponding temperature of heater radiation source was 460-644 ℃.In order to verify the universal applicability of the best band 4.0-5.0μm to asphalt pavements with different gradations.5 different grades of asphalt concrete pavements: AC-13 gradation,AC-16 gradation,AC-20 gradation,SMA-13 gradation and SMA-16 gradation were selected,the numerical simulation of the hot in-place recycling of asphalt concrete pavement infrared radiation heating process was carried out.And their best wavelength points were determined to be near 4.85μm,4.6μm,4.45μm,4.4μm and 4.7μm,which were all in the4.0-5.0μm band.It was verified that when the heating distance is 10 cm and the pulse-type intermittent heating method is adopted,the best band for the hot in-place recycling of different gradations of asphalt concrete pavements infrared radiation heating can be taken as4.0-5.0μm. |
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