The Evaluation Of Comprehensive Performance Of SMC Normal Temperature Modified Asphalt And The Asphalt Mixture

In order to solve the problems of high construction temperature,high energy consumption and high pollution emissions of traditional hot mix asphalt,the scale of using various warm and cold asphalt modifiers in the process of pavement paving getting more and more big.The SMC normal temperature asphalt modifier is one of the star products,developed by China Academy of Transportation Science.It is mainly composed of the rubber oil from waste plastic and tires,which belongs to novel cold mix asphalt modifier.It’s claims that the modifier can be transported,stored and mixed at normal temperature.SMC can not only replace the traditional cold mix asphalt to complete the reinforcement of the road,but also be used as the paving material of the full-width pavement.Now it has been developed to the third generation,and has achieved more than 1,000 kilometers of engineering application cases in less than 3years.However,the primary premise of applying warm and cold mix modifiers is that the quality of the project cannot be affected by blindly seeking to reduce the construction temperature.So in order to comprehensively investigate the properties and engineering practical value of SMC modified asphalt,this paper carries out systematic experimental research and calculation analysis in four aspects of SMC,including road performance,modification mechanism,environmental impact and economic benefit.The main work of this paper and the results are as follows.（1）Road performance:the performance of SMC modified asphalt is evaluated by using the evaluation method of liquid petroleum asphalt and the traditional three indexes test method,and its volatilization characteristic is emphatically investigated.In terms of mixture,the volume parameter,strength parameter,dynamic stability,residual stability,freeze-thaw splitting strength ratio and maximum bending strain of SMC modified asphalt mixture are tested under two gradation schemes and six dosages.The results show that:When this modified asphalt is used for road paving,the construction should be completed within 4 hours after preparing,and the maintenance time of 7 days should be guaranteed.Under AC-13gradation,the suitable dosage range of SMC is 6%-10%,and the suitable dosage range of AC-20 gradation is 6%-8%.Under the above conditions,the construction temperature can be reduced to 100℃,but it is difficult to achieve the claimed effect of"production and paving at normal temperature".Compared with conventional hot mix asphalt mixture,the low temperature crack resistance of the mixture is optimized to a certain extent after adding SMC,but the high temperature stability and water stability are deteriorated.（2）Modification mechanism:the change of functional groups in asphalt before and after adding SMC was analyzed by Fourier Transform Infrared（FTIR）.The results show that:The essence of SMC is a kind of quaternary ammonium salt surfactant containing amido groups.After SMC is added to asphalt,a dense water film is formed on the surface of asphaltenes because of the strong hydrophilicity of amido groups.（3）Environmental impact:the emission of CO₂、CO、SO₂、NO_x、PM_2.5、PM₁₀、benzo（a）pyrene from asphalt mixture during the laboratory mixing process is quantitatively detected through waste discharge test.The environmental benefit of SMC is evaluated according to the real time emission data obtained from the test.The results show that:In the laboratory test,SMC has an inhibitory effect on the discharge of seven kinds of wastes generated in the mixing process of the mixture.After adding 10%SMC,the production temperature of the asphalt mixture decreases by about 75℃,and the emission reduction effect is significant:CO₂emissions decreased by 44.6%、CO emissions decreased by 96.6%,、SO₂ emissions decreased by 78.8%、NO_x emissions decreased by 69.2%、PM_2.5 emissions decreased by 9.4%、PM₁₀emissions decreased by 8.4%、benzo（a）pyrene emissions decreased by 76.9%.In the aspects of eigenvector of three environmental impacts which are global warming,health hazards and acidification effects,SMC has a significant effect on the mitigation of health hazards.（4）Economic benefit:In combination with the survey data,the Life Cycle Assessment（LCA）method is used to assess the economic benefits of SMC modified asphalt mixture in the life cycle composed of three stages:the production,the transportation and the construction.The results show that:Under the same boundary condition,the energy saving effect of SMC is mainly reflected in the energy consumption required to heat the asphalt during the production process.Adding 8%SMC can reduce mixing temperature of the asphalt mixture by 68℃,saving nearly 40%of the fuel combustion energy consumption.The comprehensive results show that:It is almost impossible to achieve road construction at normal temperature without bad performance effects by adding SMC.There is a certain bad effect by adding SMC on the road performance of asphalt and asphalt mixture.Therefore,It is necessary to comprehensively consider the dosage of SMC asphalt modifier in combination with the quality requirements,environmental and economic benefits on the actual project.On the premise of not affecting the project quality,the effect of reducing construction temperature,energy saving and emission reduction should be given full play.It is hoped that the research results in this paper can provide reference for similar engineering cases.