Indoor Simulation Study On The Compaction And Forming Time Of Cold Mixed And Cold Laid Emulsified Asphalt Mixture

The high energy consumption and heavy pollution of hot mix asphalt mixture used in road paving restrict the sustainable development of road construction,therefore there is an urgent need to develop high energy saving and low emission asphalt mixture technology.Based on this,the research group has developed a cold mixed and cold laid emulsified asphalt mixture for road structural layers in the early stage.This material is energy-saving,emission reducing,and has excellent performance.However,due to the influence of multiple factors on its strength formation,it is difficult to grasp its compaction and forming time.The current specifications lack criteria for determining the compaction and forming time of cold mixed and cold laid emulsified asphalt mixture,which seriously affects the promotion and application of this material.Therefore,this article combines theoretical analysis and indoor experimental research to reveal the changing patterns of different factors affecting the performance of cold mixed and cold laid emulsified asphalt mixture.Referring to the technical requirements of hot mixed asphalt mixture,a criterion for determining the compaction time of cold mixed and cold laid emulsified asphalt mixture is proposed,and a prediction model for its compaction time is established.Firstly,AC-13 and AC-16,commonly used in the surface layer,were selected as the experimental gradation for mix design.Referring to the technical requirements of hot mix modified asphalt mixture and Marshall design method,the mix design was carried out based on the coating state of emulsified asphalt on the mineral aggregate.The optimal emulsified asphalt dosage and external water dosage for AC-13 and AC-16 cold mix cold laid emulsified asphalt mixture were determined.Secondly,research is conducted on the standards and methods for determining the compaction timing of cold mixed and cold laid emulsified asphalt mixtures.A fitting equation was established for the splitting strength,high temperature,low temperature,and water stability of emulsified asphalt mixture with forming time.Based on the compliance of various road performance with the specification requirements of hot mix modified asphalt mixture,the compaction time of AC-13 and AC-16 emulsified asphalt mixture was determined.On this basis,combined with the correlation analysis of splitting strength with high temperature,low temperature,and water stability,the judgment indicators and standards for the compressibility time of emulsified asphalt mixture were determined.The judgment index is the splitting strength,and the judgment standards AC-13 and AC-16 are 0.69 MPa and 0.64 MPa,respectively.Then,the mechanism analysis of the impact of compaction timing on the strength of cold mixed and cold laid emulsified asphalt mixture was conducted.Through indoor experiments,it was determined that the main influencing factors on the compaction timing of cold mixed and cold laid emulsified asphalt mixture were temperature,humidity,cement dosage,and sand equivalent.SEM electron microscopy scanning equipment was used to scan the interior of specimens compacted too early and too late.Combined with the analysis of the impact of compaction timing on the later strength of emulsified asphalt mixture,the reasons for the decrease in strength of emulsified asphalt mixture compacted too early and too late were explored,This lays the foundation for further analysis and optimization of material properties.Finally,a prediction model for the compaction timing of cold mix and cold laid emulsified asphalt mixture was established.The orthogonal design of splitting strength test was conducted using temperature,humidity,cement dosage,and sand equivalent as influencing factors.A regression equation was established for the variation of splitting strength of AC-13 and AC-16 with molding time under multiple factor combinations.The earliest and latest compaction time of cold mixed and cold laid emulsified asphalt mixture under various factor level combinations was determined based on the criteria for determining the compaction time.On this basis,the degree of influence of each factor was determined through range and variance analysis,and multiple nonlinear regression analysis was conducted on the experimental data using SPSS analysis software.A prediction model for the compaction time of cold mix and cold laid emulsified asphalt mixture was established,with high fitting accuracy.