Evaluation of Asphalt Binders Used for Emulsions

Principal Investigator(s):

Mihai Marasteanu, Professor, Civil, Environmental and Geo-Engineering

Project summary:

In recent years, increased emphasis has been placed on the preservation of asphalt pavements. Many of the technologies available for preservation, such as seal coating/cold in-place recycling, fog sealing, etc. use asphalt emulsions as a main component. However, unlike asphalt binders for which performance based specifications are available, the asphalt emulsions lack a similar set of testing procedures. This project was an effort to better characterize asphalt emulsions that are typically used in cold in-place recycling (CIR) applications. A simple approach was developed that treated the cured residue as asphalt binder and applied the standard Superpave specifications to the material. A literature review examined methods that have historically been used to produce, characterize, and apply asphalt emulsions. Four emulsions were tested in this project: CRS-2P, CSS-1, EE, and HFMS-2P. The emulsions were cured two ways, the first being allowed to sit overnight in a pan at room temperature, and the second being a modified RTFOT approach. Air cured samples were also aged in the PAV. These residues were then tested with the BBR and DT at low temperatures and with the DSR at high and intermediate temperatures. AASHTO MP1 specifications were applied in order to characterize the emulsions by PG grade. Following this, AASHTO MP1a specifications were followed in order to find the critical cracking temperature of the emulsions. Master curves were constructed from the DSR tests of complex shear modulus vs. frequency. Finally, a sample mix design was developed using these emulsions and an empirical equation to predict the dynamic modulus of the mixture.

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