| Asphalt pavement has the advantages of comfortable driving,small noise and so on,which has become the main form of road engineering.However,no matter in frozen area or rainy area,due to the impact of external environment and asphalt mixture performance,many diseases,such as rutting and cracking,may be caused in the service period of asphalt pavement,which will reduce the service life of the road and increase its maintenance cost.The method,improving the performance of asphalt mixture,is used to reduce the occurrence of pavement diseases.Previous researches show that calcium sulfate whisker and polyester fiber have a certain influence on improving the performance of asphalt mixture in some aspects.Calcium sulfate whisker will enhance the high temperature stability of asphalt mixture to some extents,while polyester fiber mainly promotes the low temperature performance of asphalt mixture.In this paper,based on the Basic Public Welfare Research Project of Zhejiang Province“Study on key technologies of multi-scale polyester fiber and calcium sulfate whisker compound modified HMAC for low temperature crack resistance”,the performance of asphalt and asphalt mixture modified by stearic acid coupling agent modified anhydrous calcium sulfate whisker and polyester fiber were studied by means of laboratory experiments.The main work has been finished as follows:1)At first,the high and low temperature of calcium sulfate whisker-polyester fiber compound modified asphalt were studied by cone penetration test,force ductility test,apparent viscosity test,bending beam rheology test and dynamic shear rheology test.Then,based on apparent viscosity test and bending beam rheology test,the viscous flow activation energy index was introduced,and the viscosity-temperature characteristics of asphalt were researched in combination with the viscosity-temperature index,the penetration index,the complex modulus index,and the viscous flow activation energy index,meanwhile,it was evaluated that the feasibility of characterizing the viscosity-temperature property of asphalt from the perspective of energy.Next,the significance of calcium sulfate whisker and polyester fibers on the performance of modified asphalt was evaluated using analysis of two-factor ANOVA.At last,the reaction mechanism of calcium sulfate whisker-polyester fiber with asphalt was revealed by SEM test,ATR-FTIR test and XRD test,respectively.2)Based on the dispersility of calcium sulfate whisker and polyester fiber,the production process of calcium sulfate whisker-polyester fiber compound modified asphalt mixture was optimized.The effects of content and addition order of calcium sulfate whisker and polyester fiber,and production temperature of asphalt mixture on the performance of asphalt mixture,dispersibility of calcium sulfate whisker and dispersibility of polyester fiber were respectivley studied through the laboratory tests,polyester fiber dispersibility test and EDS sulfur element surface scanning test.Then,the regression equations between the dispersibility index of calcium sulfate whisker-polyester fiber and asphalt mixture performances were established.At last,the optimal production parameters of calcium sulfate whisker-polyester fiber compound modified asphalt mixture,calcium sulfate whisker modified asphalt mixture and polyester fiber modified asphalt mixture,were obtained,respectively.3)The mix design of calcium sulfate whisker-polyester fiber compound modified asphalt mixture was optimized by Centeral Composite Design.The bitumen-aggregate ratio,calcium sulfate whisker content and polyester fiber content were treated as the influence factors.The void ratio,stability,dynamic stability,-10℃split tensile strength,tensile strain at break,residual stability after immersion in water,and freeze-thaw split strength ratio were treated as the response indicators.And then,the experiments of three factors,five levels and seven responses were design to explore the effect of interaction of different factors on response indicators.Next,the quadratic response surface models were established according to the results of analysis of ANOVA.Finally,the mix ratio of calcium sulfate whisker-polyester fiber compound modified asphalt mixture was optimized with the goals of high temperature stability performance,water stability performance and low temperature crack resistance,respectively.The expected values of the road performance evaluation response indicator were set,the optimal content of calcium sulfate whisker and polyester fiber and the optimal bitumen-aggregate ratio were also determined.Meanwhile,the laboratory test data were used to verify the model predictive values.4)To analyze the effect of calcium sulfate whisker-polyester fiber on the performance of asphalt mixture,four kinds of asphalt mixtures,base asphalt mixture,calcium sulfate whisker modified asphalt mixture,polyester fiber modified asphalt mixture and calcium sulfate whisker-polyester fiber compound modified asphalt mixture,were selected.The high temperature stability performance,water stability performance and low temperature crack resistance of four kinds of asphalt mixtures were studied.Then,the effect of calcium sulfate whisker and polyester fiber on the inhibition of water damage development of asphalt mixture was evaluated with the logistic damage model.Next,the grey correlation method was used to explore the correlation between the high temperature stability index and low temperature crack resistance index of asphalt mixture,the performance index of asphalt binder,and the physical and mechanical indexes of asphalt mixture,respectively.Then,the direct and indirect evaluation indicators suitable for the high temperature stability and low temperature crack resistance of calcium sulfate whisker-polyester fiber compound modified asphalt mixture were respectively proposed.5)The low temperature crack resistance and crack propagation behavior of four kinds of asphalt mixtures were studied by the pre-notched trabecular bending test and pre-notched SCB test.Two toughness evaluation indictors,stress intensity factor KIand fracture toughness JIC,were introduced to analyze the low temperature crack resistance of asphalt mixture,and the mechanism of calcium sulfate whisker and polyester fiber toughened asphalt mixture was discussed at the same time.Then,the applicability of two toughness evaluation indicators in the resistance to crack propagation of calcium sulfate whisker and polyester fiber compound modified asphalt mixture was researched.At last,the crack propagation path of the pre-notched trabecular specimen and the pre-notched semi-circular specimen were revealed from the macroscopic view during the loading failure process. |
