ARCHIVED - Bitumen Fingerprinting Allows for Improved Product Consistency

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February 05, 2005— Ottawa, Ontario

Road workers repairing asphalt
Road workers repairing asphalt

Everyone has heard of DNA fingerprinting. It is the analysis of characteristic patterns in DNA to identify individuals. Now take the same idea and apply it to bitumen, the tar-like mixtures of hydrocarbons derived from petroleum naturally or by distillation. It may not sound as interesting or as high-tech, but researchers at the National Research Council Institute for Research in Construction (NRC-IRC)'s Urban Infrastructure Program are finding that the process of "bitumen fingerprinting" they have developed is quite a handy tool.

Bitumen is an important component in a number of construction materials used for road surfacing and roofing, including polymer-modified asphalt, crack sealants, shingles and waterproof membranes. In each application, the bitumen is blended with a polymer, which can be a tricky process. There is always the possibility the mixture will separate, so once manufacturers have a mixture that works, they want to stick with it.

Crack sealant applied to aged roadways
Crack sealant applied to aged roadways

Unfortunately, the precise identity of bitumen is difficult to establish, so that two different lots with the same technical grade may have different chemical compositions. Although methods exist to analyze the composition of bitumen, they all use organic solvents that are expensive to use and to discard.

NRC-IRC researchers, however, have come up with a solventless method to fingerprint bitumen to ensure that bitumen products are consistent. It relies on a burning process called thermogravimetry (TGA), which is a method of controlled combustion that allows for measuring the temperature at which a material turns into ashes and gases. Because light, medium and heavy hydrocarbons (HC) in bitumen burn off at different temperatures, researchers can determine the chemical composition of a sample by monitoring changes in the sample's mass and the temperatures at which these changes occur.

Thermogravimetric equipment
Thermogravimetric equipment

Thermogravimetry has long been used to characterize petroleum products rapidly but has generally been plagued by poor resolution and reproducibility. The NRC-IRC researchers have overcome these difficulties, however, by using a combination of research-grade thermogravimetric equipment and a high-resolution method they have developed based on a patented algorithm. The result is improved resolution and greater reproducibility in the chemical analysis of bitumen.

Enquiries: Media relations
National Research Council of Canada

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