Asphalt breaks loose from the aggregate and powders due to microbial action. In addition, if microorganisms are present in large numbers, they produce gas, causing blisters in the roadway.
Under a state Highway Department grant, Brown determined that naturally occurring microorganisms secrete an emulsion that breaks the bond between asphalt and aggregate.
Spraying a simple and inexpensive chemical, silane— already used to waterproof concrete and some paints—onto the aggregate creates a lasting bond. Brown also found that the addition of lime to the asphalt mix retards the microbial activity.
Taxpayers and motorists in Mississippi will be happy to learn that the Highway Department is beginning to use silane in field tests.
An example of how far the news of Brown's findings has spread is the report that silane soon will be introduced as a standard road construction specification by road building authorities in South Africa.
--Abner Harrison
Updated and adapted by Chris Brown <brownc@ur.msstate.edu>.
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