Study On Aggregate Properties And Its Impact On The Mass-Transfer Of Aggregate/Emulsifier System

Uncontrollable demulsification conditions dramatically restricted the application of emulsified asphalt in road engineering.There were mainly two reasons.One was the complexity of the emulsified asphalt system,and the other was less study on the impact of aggregate on the asphalt system.The emulsified asphalt system was easy to be influenced by such factors as asphalt,emulsifier and various additive and stabilizers,among which the emulsifier was the most important one.This paper,from perspective of asphalt emulsifier and aggregate,studied the impact of aggregate properties on aggregate/emulsifier system mass transfer with relatively controllable mineral powder as aggregates in order to obtain the action mechanism and inner law between aggregates and the emulsifier.(1)Test method was improved according to specific requirements of aggregate for road industry.During the test,such parameters as surface energy,conductivity,Zeta potential,pH value and alkali value of 4 types of limestone and 1 type of basalt aggregates as well as chemical compositions contained in such aggregates(calcium oxide,magnesium oxide,iron trioxide,silicon oxide and aluminum oxide,which accounting for 95-99% of all chemical composition contents)were tested to analyze the rules of parameter change.Findings of the test were listed below:(1)Surface energy was greatly related to grain size and lithology of aggregates.Surface energy parameters tended to decrease with the decrease of grain size;(2)The conductivity of aggregates in water was increased with the increase of the aggregate content(solid-liquid ratio)and finally tended to be gentle;(3)Lithology difference of aggregates produced greater impact on Zeta potential than aggregate grain size;(4)pH value and alkali value of the aggregates were not influenced by the solid-liquid ratio,and it was not easy to tell the differences between aggregates from indicators of pH value and alkali value.(2)Grey correlation method of Grey Theory was used to analyze the correlation between surface energy parameters and other parameters such as specific surface area,granularity,aggregate grain size,ph value,alkali value,potential difference,average diameter of BJH adsorption cumulative pore,multiple-point BE specific surface area(B1)and inner specific surface area of BJH adsorption cumulative pore(B2)for above 4 types of limestone and 1 type of basalt aggregates as well as chemical compositions contained in such aggregates.According to the analysis,measured values such as surface energy,pH value and alkali value of aggregates were highly correlated to the values calculated from surface energy parameters of the chemical compositions contained in above aggregates.In order to effectively differentiate aggregates with different lithological characters,a model of relationship between the "physical and chemical properties of aggregates" & "chemical composition content"(which will change based on surface energy,pH value and alkali value)and the unchanged "physical and chemical properties of aggregates" was established with data analysis and statistics software SPSS 22.0.(3)In order to study the aggregate/emulsifier interphase mass transfer from perspective of adsorption coefficient,MQK-1d and SDBS emulsifiers were respectively mixed with five types of aggregates and five chemical compositions and impact of emulsifier concentration and solid-liquid ratio on the adsorption coefficient of the aggregate/emulsifier solution system was analyzed.According to the test,similar results were obtained when conductivity and absorbency of the emulsifier/aggregate(aggregates and chemical compositions)system were assessed from perspective of adsorption coefficient,i.e.,solid-liquid ratio was obviously more correlated to the adsorption coefficient of the emulsifier/aggregate(aggregates and chemical compositions)system than emulsifier concentration.According to the test results,key indicators influencing the adsorption coefficient of both emulsifiers(MQK-1d & SDBS)and five chemical compositions were specific surface area parameters such as multi-point BE specific area(B1),BJH adsorption cumulative pore volume(B5),and surface energy parameters such as alkali component,pH value,and theoretical alkali value.Key indicators influencing the adsorption coefficient of Emulsifier MQK-1d/ aggregates system were specific surface area parameters such as B3,B4,B5 and surface energy parameters such as dispersion component,acid component,surface energy,granularity D75,conductivity,and contents of iron trioxide,magnesium oxide and calcium oxide;Key indicators influencing the adsorption coefficient of Emulsifier SDBS/aggregate system were specific surface area parameters such as B2,B3,B5 and surface energy parameters such as polarity component,alkali component,potential of electrochemical indicators as well as aluminum oxide content and silicon oxide content.