Preparation And Performance Evaluation Of Unsaturated Polyester Heat-reflective Coating For Asphalt Pavement

Asphalt pavement is endowed with the advantages of high evenness,comfortableness and low noise,and has been wildly applied in highway construction in China;however,as a black pavement,the asphalt pavement has strong heat absorptivity,especially during hot seasons,the temperature of which is relatively high.Not only the pavement in high temperature is easily produced thermal stability diseases,but also emits a lot of radiant heat,which will aggravate urban heat island effect.In view of the negative effect caused by asphalt pavement,in this paper,a kind of unsaturated polyester heat-reflective coating(UPRC)with high reflectivity and good pavement performance was prepared.Applying this coating on asphalt pavement can effectively decrease the pavement temperature,and thus lessen thermal stability deseases and mitigate urban heat island effect.The fundamental features and components of heat-reflective coating were analyzed firstly,and then connecting with the pavement demand,unsaturated polyester(UPR)was chosen as base material.Methyl methacrylate and butyl acrylate were used to modify UPR.Orthogonal design was applied to obtain optimized base material prescription with good flexibility and viscosity.TiO2,SiO2 and hollow glass bead were selected as main functional fillers.Optimal coating formula with suitable viscosity,good cooling effect and low glossiness was derived through orthogonality experiments.At last,color UPRC was prepared by adding different color pigment.The reflectivity of color UPRC reaches 74.4%.In addition,by means of characterizing the microstructure and researching on the performance of the coating,the curing mechanism of the base material and cooling principle were obtained.It is presented that the cooling effect is deriving from high reflectivity in visible band and near infrared band and high radiation ability in atmospheric window.The performance parameters were tested and its technical indexes were put forward accordingly.The asphalt pavement with UPRC can be called UPRC pavement.The cooling effect of UPRC pavement was evaluated by indoor and outdoor tests.In lab experiments,iodine tungsten lamp was used to simulate solar radiation.The cooling effect of UPRC applied on dense-graded pavement,stone mastic asphalt pavement and open-graded friction course pavement with different dosage were studied respectively.Through these experiments,Optimal contents in different aggregate grading asphalt concrete were put forward.The cooling effect was compared with the coating contaminated in different degree.The accelerated ageing test was also carried out to study the change of cooling effect.These experiments demonstrate that the cooling effect is reduced to some extent when being contaminated,but the coating still keeps good cooling effect after ageing.In outside experiment,it can be founded when asphalt concrete pavement reached around 60 ?,UPRC can reduce pavement temperature about 8?9 ?.The abrasive resistance,temperature-change resistance,water permeability and adhesion of the coating to pavement surface were evaluated.The impact of UPRC on high temperature stability of asphalt pavement was also analyzed.The results indicate UPRC pavement has good pavement performance.The skid resistance of the UPRC pavement with different kind of grading type was studied and the corresponding skid-resistant methods were proposed.After adding the anti-skid granules,the skid resistance is greatly improved and UPRC pavement can keep good wearing resistance,moreover,the anti-skid granules have little effect on temperature reduction.The construction technology was studied and then the construction processes were brought forward.UPRC pavement of test section was constructed and the pavement temperature was measured;tests prove the reduction value of the pavement temperature reaches around 9? at two centimeters deep.UPRC has a high reflectivity in visible and near infrared band,however,atmosphere has a poor energy absorption capability in these two bands,so the reflected energy can penetrate atmosphere to a great extent,and thereupon UPRC can reduce heat radiation from pavement to atmosphere and thus mitigate urban heat island effect.By calculating heat radiation equation of the pavement,it is found that the radiation energy value of asphalt pavement is about five times bigger than that of UPRC pavement.A self-made heat radiation testing device was used to contrast the atmospheric attenuation of infrared radiation above the asphalt pavement and UPRC pavement,which proofs that the heat radiation energy is more easily absorbed by atmosphere above asphalt pavement.Lastly,a computational fluid dynamics software CFX was used to set up a numerical model of temperature field of asphalt pavement,UPRC pavement and atmosphere.