The need for a standard test method that would allow the determination of the complex shear modulus of bituminous mixtures using relatively inexpensive laboratory equipment has led to the development of a new ASTM International standard, D7552, Test Method for Determining the Complex Shear Modulus (G*) of Bituminous Mixtures Using Dynamic Shear Rheometer.
D7552 was developed by Subcommittee D04.26 on Fundamental/Mechanistic Tests, part of ASTM International Committee D04 on Road and Paving Materials.
According to Gerald Reinke, president, MTE Services Inc., and a D04 member, D7552 will be useful in field testing as well as in laboratories.
“The test enables operators to determine the complex shear modulus of field cores, regardless of layer thickness,” says Reinke. “This functionality makes the test a good tool to provide forensic analysis of field mixtures.”
Reinke says that among the practical applications of the new standard is the ability to determine that a mix design has been duplicated in actual production. “A field quality control mix sample can be prepared and tested within three to four hours if the proper test equipment is available,” Reinke notes. “Additionally, if there are questions as to the quality or consistency of mix being placed on the road, field cores can be cut, prepared and tested within a similar time period.”
Independent testing laboratories specializing in the forensic investigation of projects will be the primary users of D7552. Labs that are engaged in research about the impact of aging time and temperature on the commingling of RAP and/or shingle asphalt on the stiffness modulus of bituminous mixtures will also find the standard useful, according to Reinke.
Technical Information: Gerald Reinke, MTE Services Inc., Onalaska, Wis.
ASTM Staff: Daniel Smith