Study On Drying Behavior Of Emulsified Asphalt And Its Influence On Mechanical Properties Of Mixture

Emulsified asphalt is widely used in pavement maintenance and regeneration projects due to its good fluidity at room temperature and easy construction.However,the viscosity of emulsified asphalt at room temperature is very low,and the emulsified asphalt mixture mixed at room temperature requires a long curing time during application,which greatly prolongs the time for open traffic and limits the application of emulsified asphalt.Essentially,the drying behavior of emulsified asphalt and the mixture has an important influence on the mechanical properties of cold recycled mixture because the adhesion ability of emulsified asphalt depends on the residual water in emulsified asphalt.Only after the water in the emulsified asphalt is completely evaporated to form a complete and continuous asphalt film,the emulsified asphalt restores the original adhesion ability of the asphalt.However,there are few studies on the drying process of emulsified asphalt at present,and its influence on the mechanical properties of emulsified asphalt mixture is not discussed from the perspective of the drying process.The content and results in this work are as follows:The relationship between water loss and time was established by the gravimetric method.Based on the emulsion drying model,the drying process of emulsified asphalt and emulsified asphalt mortar was divided into three stages.In the first stage,the water evaporated at a high rate.In the second stage and the third stage,the evaporation rate is small but constant.The critical points of the three stages are determined according to the emulsion drying model.The water loss rate and the cumulative water loss curve,and the drying process is evaluated by the maximum particle volume fraction ф＿max.The effect of the particle size on the drying process of emulsified asphalt was studied.The results show that the smaller the particle size,the greater the accumulated water loss.The larger the maximum particle volume fraction,and the better the drying effect.The results show that the addition of mineral powder mainly affects the whole drying process by reducing the drying rate of the second stage.In contrast,the effect of limestone powder is more obvious than that of granite powder.The drying behavior of three different particle sizes of emulsified asphalt was characterized by AFM.The results show that,from the topography of the sample,with the increase of time,the asphalt particles further fuse to form an asphalt film.The surface of the sample becomes more smooth and the asphalt film changes from incomplete and uneven to complete and uniform.The adhesion force also transitions from an initial non-uniform to a uniform state.The smaller the particle size,the more obvious the fusion effect of the particles,the smoother the surface,the more complete the formed asphalt film.The effects of particle size and cement content on the mechanical properties of the mixture were studied.The results show that the splitting strength of emulsified asphalt mixture with different particle sizes will increase continuously,while the splitting strength decreases continuously with the increase in the particle size of emulsified asphalt.