Contribution of Microorganisms to Stripping of Asphalt Pavements

摘要

Stripping, as the term is applied to asphalt pavements, refers to the breaking of the adhesive bond between the gravel and the asphalt. There are a variety of ways in which stripping occurs but the net result is a washing away of the asphalt from the gravel. Since microbes produce surfactants and emulsifying agents that could accelerate the process, the question arises as to whether they play a meaningful role in the stripping process. Preliminary analyses of stripped asphalt samples confirmed the presence of both aerobic and anaerobic microbes. Other studies have shown that microbial growth accelerates the stripping process. Coating the gravel with an organofunctional silane prior to the addition of asphalt retards the stripping process at a concentration of 1/150 v:v in water even in the presence of vigorous microbial activity. The silane treatment (1/150) was found to be effective in retarding stripping by both indigenous microbes and a bacterium known to produce an emulsifier. Lime (1%), incorporated into the asphalt mix, prevented microbial growth and stripping but was not as effective as the silane treatment.