PURPOSES : The purpose of this study is to examine the manufacturing method for emulsified asphalt and its bond performance by analyzing the properties of the emulsifier used to produce cold recycled asphalt mixtures. METHODS: In this study, four types of slow-setting cationic emulsifiers, a microsurfacing emulsifier, and six types of nonionic emulsifiers were used to manufacture emulsified asphalt. Because each emulsifier requires its own unique effective dose to provide the best performance, the optimum asphalt content for each effective dose was determined. Then, the optimum asphalt content for the emulsified asphalt mixture was determined by the tests to check its basic physical properties. By using the determined optimum content, asphalt mixtures were manufactured and dynamic immersion and tensile strength tests were conducted on the mixtures to analyze the influence of the emulsifier on the physical properties of the mixtures. RESULTS : The dynamic immersion test results showed a coating ratio of 54-85%, which is considerably higher than that of using ordinary straight asphalt. The tensile strength test yielded noncompliant values less than 0.4 N/mm, which is the standard requirement for dry indirect tensile strength. The correlation analysis between the dynamic immersion and tensile strength ratio tests showed very high correlation of 0.78. The correlation between the emulsifier content and water resistance performance was low, between -0.55 and -0.24. CONCLUSIONS : While the storage stability improves with increasing emulsifier, the effectiveness proportional to the increase is weaker as the emulsifier increases. The performance testing of asphalt residues before and after manufacturing the emulsified asphalt showed no significant change. It is proved that the emulsified asphalt maintains high coating resistance according to the dynamic immersion test results. In addition, according to the results of tensile strength ratio, cold recycled asphalt mixtures manufactured by the materials normally and commercially used are not compliant with the national standard specification; thus, additional effective materials will be needed for quality compliance. In conclusion, it is evident that the dynamic immersion and tensile strength ratio tests have good correlation, but the quantity of emulsifiers used is not related to the level of moisture resistance.

PURPOSES: The purpose of this study is to evaluate the mechanical properties of a cold-recycling asphalt mixture used as a base layer and to determine the optimum emulsified-asphalt content for ensuring the mixture’s performance. METHODS: The physical properties (storage stability, mixability, and workability) of three types of asphalt emulsion (CMS-1h, CSS-1h, and CSS-1hp) were evaluated using the rotational viscosity test. Asphalt emulsion residues, prepared according to the ASTM D 7497-09 standard, were evaluated for their rheological properties, including the G*/sinδand the dynamic shear modulus (|G*|). In addition, the Marshall stability, indirect tensile strength, and tensile-strength ratio (TSR) were evaluated for the cold-recycling asphalt mixtures fabricated according to the type and contents of the emulsified asphalt. RESULTS: The CSS-1hp was found to be superior to the other two types in terms of storage stability, mixability, and workability, and its G*/sinδ value at high temperatures was higher than that of the other two types. From the dynamic shear modulus test, the CSS-1hp was also found to be superior to the other two types, with respect to low-temperature cracking and rutting resistance. The mixture test indicated that the indirect tensile strength and TSR increased with the increasing emulsified-asphalt content. However, the mixtures with one-percent emulsified-asphalt content did not meet the national specification in terms of the aggregate coverage (over 50%) and the indirect tensile strength (more than 0.4 MPa). CONCLUSIONS : The emulsified-asphalt performance varied greatly, depending on the type of base material and modifying additives; therefore, it is considered that this will have a great effect on the performance of the cold-recycling asphalt pavement. As the emulsified-asphalt content increased, the strength change was significant. Therefore, it is desirable to apply the strength properties as a factor for determining the optimum emulsified-asphalt content in the mix design. The 1% emulsified-asphalt content did not satisfy the strength and aggregate coverage criteria suggested by national standards. Therefore, the minimum emulsified-asphalt content should be specified to secure the performance.