Study On Influence Of Hygroscopic Characteristic Of Fine Aggregate On Water Stability Of Warm Mix Asphalt

Organic wax additive warm-mix asphalt mixture(Warm Mix Asphalt,WMA)are widely used due to their low carbon and energy saving characteristics,but their water stability performance has always been the focus of attention,the moisture absorption characteristics of the fine aggregates are directly related to the water stability of WMA.In view of the water stability of WMA,by analyzing the hygroscopic characteristics of different types and sizes of fine aggregates(absorption-loss discipline),study on the change of micro pore size distribution of fine aggregate before and after heating by means of low temperature nitrogen adsorption,propose the most sensitive particle size range for fine aggregate,evaluation of the change of adhesion between water-sensitive fine aggregates and asphalt by agitated water net adsorption method,and establish the correlation between adhesion and WMA water stability,propose the control range of water content of fine water-sensitive aggregate,optimize the actual mixing process to provide sufficient theoretical basis for improving the water stability of the organic wax warm mixed asphalt pavement.In this paper,the organic wax additive is Sasobit warming agent,and the fine aggregate is limestone,basalt and steel slag.First,through the indoor design water absorption test,the water absorption performance of different types and sizes of fine aggregates under different temperature and humidity conditions was analyzed.The increasing trend of the water content of different types and sizes of fine aggregates with time was analyzed.The relationship between specific surface area and water absorption law was established.The specific surface area of the particle size decreases from 0.075 mm to 0.3mm,and the specific surface area of the fine aggregate with a particle size from 0.6mm to 4.75 mm decreases less,indicating that the change in specific surface area is not uniform between different particle sizes.The greater the change,the water absorption capacity of fine aggregates with different particle sizes is affected by their specific surface area.The water absorption capacity of fine aggregates with different particle sizes is ranked as:0.075mm>0.15mm>0.3mm>0.6mm> 1.18mm>2.36mm>4.75 mm.Secondly,the water loss rule of fine aggregates of different types and particle sizes was studied,and the pore structure changes of fine aggregates before and after water loss were tested by low temperature nitrogen adsorption method.The results show that:due to the fine aggregates being subjected to various Influenced by different factors,the surface pore size distribution is uneven.By comparing the pore size distribution in the two states,it is found that the pore size distribution of 0.3mm fine aggregates changes the most.After heating,the surface moisture is more difficult to dissipate and is most sensitive to moisture.Finally,based on the agitated water net adsorption method,the adhesion between 0.3mm fine aggregate and asphalt was studied,and the correlation between aggregate-asphalt adhesion and WMA water stability performance was established.It was found that 0.3mm fine aggregate residual moisture content when it is 0.4%,the adhesion to asphalt changes suddenly,and the 0.3mm fine aggregate-asphalt adhesion has a linear relationship with WMA water stability.Therefore,in order to ensure that WMA has good water stability during production,it is recommended to control the residual moisture content of the 0.3mm fine aggregate is within 0.4%.