Research And Application Of Cold Recycled Mixtures With Emulsified Asphalt Based On The Theory Of Three-level Dispersion

There are two theories for the strength formation of asphalt mixtures,one is the traditional surface theory and the other is the modern mastic theory.The traditional surface theory holds that the asphalt mixture consists of aggregate skeleton（composed of coarse aggregate,fine aggregate and filler）and asphalt.The asphalt is distributed on the surface of the aggregate skeleton,and the aggregate skeleton is cemented to an integral whole with a high strength.While the modern mastic theory believes that the asphalt mixture is a dispersion system of a three-level spatial network structure.Firstly,asphalt mastic is a kind of micro-dispersion system in which the filler is dispersed in the asphalt medium,then the asphalt mortar is a fine dispersion in which the fine aggregate of particle size≤4.75 mm is dispersed in the mastic medium.Finally,the asphalt mixture is a coarse dispersion in which the coarse aggregate is dispersed in the mortar medium.The mastic theory believes that the asphalt mastic is the most important among the three dispersions,and its composition and structure will affect the high and low temperature properties of the asphalt mixture.Based on the theory of three-level dispersion of asphalt mixture,the performance,influencing factors and influence mechanism of micro-dispersion mastic and coarse-dispersion cold-recycled mixtures with emulsified asphalt（CRME）were systematically studied,and then the application and performance verification of CRME in pavement engineering were carried out on the basis of work indoors.The results of the research showed that:The hydrophilicity coefficient,density,fineness modulus,P₂₀ and D₁₀ of the mineral powder should be analyzed and evaluated as key indicators when it is applied,since the characteristics of the filler have a direct influence on the performance of micro-dispersion mastic.And it has important guiding significance for improving the performance of the mineral powder-asphalt mastic and CRME.The addition of cement can increase the modulus of the hydrate-residue mastic and CRME while also reducing the stress-strain reaction time of the two systems,indicating that the influence of cement on rheological properties of micro-dispertion and the dynamic mechanical properties of coarse-dispersion is consistent.This indicates that the three-level dispersion structure of the modern mastic theory can be used to explain the strength formation process and mechanism of CRME.In addition,the clustered hydration product formed after adding cement can be intertwined with the demulsified asphalt film to form a spatial network structure which acts like a“reinforcing bar”in the micro-dispersion mastic and CRME.This affection not only increases the interfacial adhesion coefficient of the mastic but also improves the interfacial adhesion properties of CRME,so that the splitting strength of CRME can be greatly improved by the hydrate-residue mastic.At the same time,the hydration product can also play a role of“modulus buffering”on the RAP surface:the modulus difference between the aged asphalt and evaporation residue of emulsified asphalt（EAR）is reduced due to the participation and influence of the hydration product after adding cement in CRME.Therefore,the strain difference between the two sides of the bonding interface under load is reduced and the coordination of the deformation inside the mixture is greatly increased,so that the mechanical properties of CRME can be greatly improved by the hydrate-residue mastic.It is found that the conventional performance and deflection value of CRME can meet the requirements of construction technical specifications and provide qualified road performance through the construction practice and performance verification of the cold recycled pavement structure design and cold regeneration of emulsified asphalt as the base layer in pavement engineering.Moreover,the stone cost and energy consumption cost can be saved by nearly700,000￥and 250,000 to 350,000￥respectively per 1 km of pavement engineering（the road width is 22 m）when CRME is used as the base layer compared with LSPM（Large Stone Porous Asphalt Mixes）.