| Asphalt pavement has been widely used in the construction of high-grade highways because of the advantages of simple maintenance and good driving comfort.The asphalt in the high-temperature state released a large amount of asphalt fumes,will not only cause pollution to the environment,but also affect the health of construction workers.Domestic and foreign scholars on the compound fume-suppressing asphalt has launched a large number of experiments and theoretical research,most rely on the fume retardant empirical compounding trial method,no unified compounding theory,so it will increase the amount of redundant testing.In addition,there is less research on the fume production characteristics of asphalt mixtures,and the theoretical results cannot be applied to practical engineering.To solve the above problems,this paper establishes the theory of optimal compounding of fume-suppressing asphalt based on genetic algorithm,and establishes a prediction model for the fume production rate of asphalt mixture based on the fume production characteristics of asphalt and mixture,and then evaluates the fume suppression and emission reduction effect of optimal compounding of fume-suppressing asphalt pavement.The main contents and conclusions are as follows:（1）The selected fume retardant is divided into two types of process preparation of fume-suppressing asphalt,with the help of high magnification microscope observation of fume-suppressing asphalt,fume-suppressing asphalt for three major indicators test,and the use of homemade asphalt fume generation-enrichment device for asphalt fume production test,the introduction of fume suppression rateωas an indicator to entropy weighting method of needle penetration,ductility,softening point and fume suppression rate for weighting calculation.The research shows that fume retardant uniformly dispersed in asphalt,no agglomeration phenomenon.Comparing the color change of U1filter tube before and after asphalt fume collection,it shows that this asphalt fume enrichment method has high reliability.The optimization functions of SK-90 and ZH-90 single-doped fume-suppressing asphalt are given.（2）With the optimization function as the objective function,refer to the current specification and fume suppression rate results set constraints,design the genetic algorithm based on fume-suppressing asphalt compounding ratio optimization program.It is shown that the number of iterations converged in both SK-90 and ZH-90 asphalt is smaller than the initial set number of iterations terminated,which indicates that the model is efficient.Due to the variability of asphalt oil sources,SK-90 and ZH-9 asphalts have different objective function values obtained after optimization operations.The four optimized compounding ratios and the corresponding four sets of predicted values of needle penetration,ductility,softening point and fume suppression rate were determined.（3）High magnification microscopy observation,segregation test,FTIR test and three major index tests on optimized compounded fume-suppressing asphalt,and verification of the reliability of the performance prediction index.MSCR test,LAS test and BBR test were carried out to analyze the change pattern of high,medium and low temperature performance of optimized compounded fume-suppressing asphalt.The study shows that the optimized compounded fume retardant is uniformly dispersed in the asphalt,which does not change the characteristic functional group of asphalt,and the asphalt has good storage stability.After adding compounded fume retardant,SK-90 and ZH-90 asphalt ductility,needle penetration are decreasing trend.The softening point of the optimized compounded fume-suppressing asphalt prepared from SK-90 asphalt is smaller compared to the softening point of the base asphalt,while the softening point of the optimized compounded fume-suppressing asphalt prepared from ZH-90 asphalt is larger.The average relative error between predicted and tested values of needle penetration,ductility and softening point indexes is less than 10%,which indicates the veracity of the predicted values of performance indexes.The optimized compounded fume retardant has improved the high and low temperature performance of asphalt.The fatigue life of the optimized compounded fume-suppressing asphalt is higher than that of the base asphalt,indicating that the optimized compounded fume retardant improved the medium-temperature fatigue resistance of the asphalt.（4）The fume production test was conducted on the optimized compounded fume-suppressing asphalt and its mixture,and the prediction model of the fume production rate of the mixture was established based on the aggregate specific surface area theory-area reduction method,and the fume suppression and emission reduction characteristics of the optimized compounded fume-suppressing asphalt pavement were analyzed.The study shows that the fume suppression rate of the optimized compounded asphalt is greater than the maximum fume suppression rate of the single asphalt,and the fume production rate of the mixture are increased with the increase in temperature.In addition,the fume production results show that SMA-13 grade type mixture has the smallest fume production rate.A model for predicting the fume production rate of densely graded and OGFC asphalt mixtures was derived by combining the measured values from indoor tests.From the perspective of fume suppression and emission reduction analysis,the optimized compounded fume-suppressing asphalt pavement has significant fume suppression and emission reduction effect,and with the carbon emission of 0.701kg as the benchmark,the emission reduction of the best emission reduction pavement is 0.6989kg. |
