Research On Heat Dissipation Characteristics And Construction Control Of Thin Overlay Of Asphalt Mixture

With its outstanding advantages,the thin overlay technology has become one of the most developed and applied maintenance technologies among various preventive maintenance technologies.It has been adapted to the changes in China’s road transportation industry from highway construction to highway maintenance.By studying the temperature dissipation characteristics of the thin overlayer during construction,we can provide guidance to the organization of rolling operations from the perspective of compaction temperature to ensure the quality of the thin overlay.The rolling quality of the surface is to ensure the good road performance of the thin overlayer.Based on the theory of heat transfer,this paper establishes the heat conduction equation and boundary conditions applicable to the temperature field of the paved layer during the rolling process of the thin overlay.With the help of ABAQUS finite element calculation software,a simulation model of temperature field is established.Based on the orthogonal experiment theory,the paper has analyzed and compared the sensitive relationship between each factor and the temperature change.What’s more,the paper has determined the significant factors,and analyzed the relationship between different factors and the temperature loss during the construction period of the thin overlay.The control temperature and the effective compaction time has been reserched,and an estimate model is obtained,which provides a theoretical basis for the compaction operation organization.First of all,based on the basic theory of heat transfer and the specific condition of the thin overlay during construction,the heat change of the paving layer is affected by three main parts:the convective heat transfer between air and the thin overlay;the radiant heat transfer;the sensible heat and latent heat of the sprinkling water during rolling.The effect and duration caused by roller sprinkling water were determined through laboratory experiments.The governing equation is obtained,which can be used as a theoretical support for establishing a numerical model.Secondly,the ABAQUS finite element software is used to establish a numerical simulation model,and the method of setting the model is discussed.PARK temperature model is introduced to simulate the initial temperature distribution of the pavement structure before construction.Intel Visual FORTRAN Compiler is used to edit external subroutines to achieve boundary conditions.By comparing the field-measured data with the simulation results of the model,the model has a better simulation of the temperature field during the construction period of the thin overlay.Then,with the help of laboratory experiments,the controlled temperature of effective compaction time during the construction period of the thin overlay of AC-13mixture with SBS modified asphalt as cement is confirmed.The paper divides factors into two groups:construction parameters and environmental parameters.Based on the orthogonal test theory,the paper has used the established simulation model to analyze the effect of each factor on the temperature loss of the thin overlay during the construction period.The research results indicate that the sensitivity order of the influence of construction parameters on temperature loss is paving temperature>watering amount>thin layer thickness>mixture type;environmental parameters are ranked as air temperature>wind speed>solar radiation.Determine the paving temperature,the amount of sprinkler water,the thickness of the cover,the temperature and the wind speed as the significant influencing factors on the temperature loss during the construction period of the thin overlay.Among them,the paving temperature,the thickness of the thin layer surface,the air temperature and the temperature loss rate have a negative correlation.The larger the value of the paving temperature,the thickness of the thin layer surface,and the air temperature are,the lower the temperature loss rate of the thin layer surface is.There is a positive correlation between the amount of sprinkled water and wind speed and the temperature loss rate.The larger the value,the greater the temperature loss rate,and the shorter the effective compaction time.At the same time,the larger the thickness of the thin overlay and the greater the wind speed,the greater the temperature difference between the surface of the thin overlay and the layer inside,and the more affected the uniformity of the compaction of the thin overlay.Finally,with the help of MINITAB,a great data analysis software,an estimation model of effective compaction time of thin overlay construction is obtained:F=0.23x₁-0.0025x₂+0.72x₃+0.17x₃ ²-0.11x₄+0.0088x₄ ²-0.37x₅-31.3.Based on this,the operation organization of roller compaction construction is exemplified with the actual conditions of the project.It is very convenient to guide the construction of thin overlay,and provides theoretical guidance for ensuring the construction quality of thin overlay.