A new ASTM international standard on the solubility of asphalt will provide an alternative for a solvent that has been banned as an ozone depleter by the Kyoto Protocol, an international environmental treaty with the goal of stabilising greenhouse gas concentrations that may help minimise global warming.

The new standard, ASTM D7553, Test Method for Solubility of Asphalt Materials in n-Propyl Bromide, was developed by Subcommittee D04.47 on Miscellaneous Asphalt Tests, part of ASTM International Committee D04 on Road and Paving Materials.
According to Stephen Burhans, manager, asphalt quality assurance/quality control, Paramount Petroleum Corp, and a D04 member, the main impetus for developing ASTM D7553 was that almost all asphalt specifications have a requirement for a maximum amount of insoluble matter to ensure that undesirable materials are not blended into the products.
However, the specified test to verify conformance (D2042, Test Method for Solubility of Asphalt Materials in Trichloroethylene) is now rarely used because trichloroethylene is a chlorofluorocarbon (CFC) banned by the Kyoto treaty.

N-propyl bromide
The solvent covered by ASTM D7553, n-propyl bromide, has been approved by the US Environmental Protection Agency under its Significant New Alternatives Policy as an alternative to chlorofluorocarbons. Committee D04 had previously approved n-propyl bromide as a trichloroethylene replacement in ASTM D2172, Test Methods for Quantitative Extraction of Bitumen from Bituminous Paving Mixtures.
“Since ASTM D7553 does not have a complete multi-laboratory precision statement, it cannot yet be substituted in the various specifications for buying and selling purposes,” says Burhans. “We will be working with ASTM’s interlaboratory studies staff to seek participants in a round robin study to develop a complete precision statement later this year.”