Study On The Effects Of Formation And Stability For Emulsified Asphalt

In this paper, based on the composition of the system, the influence rules of the formation and stability of emulsified asphalt were studied. The emulsification degree in the process of the emulsified asphalt formation was characterized by the oil-water interfacial tension, and the stability of emulsified asphalt was characterized by its storage stability and the average particle size; the effects of emulsifiers, additives, pH value of soap solution, asphalt types on the oil-water interfacial tension and stability of emulsified asphalt systems were investigated; the relationship amongst the interfacial tension, the stability of emulsified asphalt and the composition and properties of the asphalt were mainly studied using linear correlation analysis and gray entropy correlation analysis; furthermore, the relationship between interfacial tension and stability of emulsified asphalt was analyzed. The results showed that:For KSH asphalt, ZH asphalt, SK asphalt and KL asphalt with similar basic properties such as penetration, softening point, ductility showed great differences in terms of the four-components, elemental composition, the nuclear magnetic resonance spectrum(NMR) and the infrared spectrum(IR). Relative to KSH asphalt and ZH asphalt, the KL asphalt and SK asphalt displays lower hydrogen to carbon ratio, higher content of heteroatom, higher ratio of aromatic and naphthenic carbon, lower alkyl carbon rate and higher molecule polarity.Emulsifiers and pH value of soap solution were the main factors affecting the interfacial tension of the emulsified asphalt system. The abilities to reduce the interfacial tension generated by the the interaction between different emulsifiers and asphalts were different. The abilities of three kinds of single emulsifiers to reduce the interfacial tension under the same conditions from small to large order were as follows : LAS, OP, 1831, while the ability of compound cationic emulsifier MQK to reduce the interfacial tension was greater than the compound anionic emulsifier ER; Relative to MQK emulsified asphalt system, the interfacial tension of ER emulsified asphalt system was affected much more by the pH value, and the suitable pH ranges were 11 ~ 12 and 1 ~ 3 respectively; the laws which interfacial tension of four kinds of asphalts changes with emulsifier and the pH value were almost the same, because the compositions and structures of asphalts were different, so the interfacial tension was different under the same conditions and the order from large to small is KSH、ZH、SK、KL.Distinct types of additive showed different effects on the interfacial tension of emulsified asphalt systems. For ER emulsified asphalt system, since CMC-Na displayed no interfacial activity, it failed to reduce oil-water interfacial tension. And for MQK emulsified asphalt system, the interfacial tensions of four asphalt all reduced and tended to be stabilized with the increase of CaCl2 mass concentration. Change laws of the interfacial tension with varied CaCl2 mass concentration in four asphalt systems are consistent, but the difference in interfacial tension showed no apparent regularity.The relationship amongst the interfacial tension and the composition and properties of the asphalt was mainly studied using linear correlation analysis and gray entropy correlation analysis. The interfacial activity is expressed by the interface pressure, so the greater the interfacial pressure, the higher the asphalt interfacial activity. Linear correlation analysis and gray entropy correlation analysis were conducted on the interface pressure, composition and properties of asphalt. The results showed that the basic properties of the asphalt cannot explain the degree of the interface pressure; For the four-component composition, the higher the asphaltene content, the higher the asphalt activity; for elements, the higher the heteroatom content,the higher the asphalt activity; In the average structural unit, the higher the aromatic carbon ratio, naphthenic carbon ratio, the condensation degree parameter of aromatic ring system and hydrogen replace rate surrounding the aromatic ring system, the lower the alkyl carbon rate and the alkyl chain branching degree, the higher the asphalt interfacial activity.There were a consistency and a better correlation between the effects of emulsifier mass concentration and soap pH value on its average particle size and storage stability, they were the principal factor affecting the stability of the emulsified asphalt system. For ER and MQK emulsified asphalt systems, the particle size and stability substantially reduced with the increase of the emulsifier mass concentration and tended to be stabilized. The particle size and stability decreased with the pH increase of soap liquid in the ER emulsified asphalt system, while, in the MQK emulsified asphalt system, the particle size and stability increased with the increase of soap pH and then tended to be stabilized. Stability performances of four kinds of emulsified asphalt follow the decreasing order: KSH>ZH> SK>KL.For the ER emulsified asphalt system, CMC-Na was able to significantly improve the storage stability of emulsified asphalt but shows no effect on the average particle size of emulsified asphalt; In MQK emulsified asphalt system, there was a consistent effect of CaCl2 on the average particle size and the storage stability of the emulsified asphalt. Emulsified asphalts prepared by four kinds of asphalt systems on the same conditions showed no apparent regularity in the size order of its average particle size and the storage stability.For emulsified asphalt system, the storage conditions were also important factors affecting its stability. Due to negligible influence of storage temperature on average particle size and storage stability of emulsified asphalt, the storage temperature is unlikely to be the principal factor affecting stability of emulsified asphalt. While the storage time has a greater effect on emulsified asphalt storage stability but slight effect on its average particle size, emulsified asphalt during storage time. The comparative stability degree order of four kinds of emulsified asphalt systems presented no change.The relationship amongst the stability and the composition and properties of the asphalt was mainly studied using linear correlation analysis and gray entropy correlation analysis. The stability of emulsified asphalt is expressed by its storage stability. The bigger the absolute value of storage stability, worse the stability of emulsified asphalt. Linear correlation analysis and gray entropy correlation analysis were performed on the emulsified asphalt stability and its composition and properties. The results showed that there was a better correlation between the stability of emulsified asphalt and asphalt four-component composition. And further properties cannot explain the stability of emulsified asphalt. In the four components, the content of resin and asphaltene were the main factors influencing the stability of the emulsified asphalt system,and the higher content of resin plus asphaltene, the better the stability of emulsified asphalt.In terms of the relationship between interfacial tension and the stability of emulsified asphalt, for ER and MQK emulsified asphalt system, the applicable laws of emulsifier dosage and soap pH on the interfacial tension and the storage stability of emulsified asphalt were basically identical. The lower the interfacial tension, the better the stability was. While auxiliaries had different effect laws on the interfacial tension and emulsified asphalt storage stability. The relationship amongst the interfacial tension, the stability of emulsified asphalt and the composition and properties of the asphalt were inconsistent. The polarity of asphalt was the principal factor to affect the interfacial tension, while, the existence and the state of dispersion of asphaltene,thickening and synergistic of resin and asphaltene were the principal factors to affect the stability.