A study shows that some bacteria can prevent cracks in asphalt

Scientists from Drexel University in Philadelphia demonstrate that the bacterium Sporosarcina pasteurii could prevent the breakdown of asphalt

The proper maintenance of the condition of asphalt depends on a wide variety of factors, from the type of vehicle that travels over it to the weather conditions it endures.

Regarding the latter, during freezing periods it is common to spread salt on the asphalt to prevent the formation of the dreaded sheets of ice. Whether by spreading from trucks or by salt-water sprinklers, sodium chloride works by preventing liquid water from crystallising when temperatures drop below zero.

Afterwards, the water returns to a liquid or vapour state and common salt is left along the edges of the roadway or on the asphalt. If it reaches the roadside ditch, sodium chloride can cause dehydration of plants, damaging the flora and fauna bordering the road. But when it remains on the asphalt, its action is also harmful and damaging to the roadway itself.

Microorganisms against asphalt degradation

When salt comes into contact with calcium hydroxide, a compound derived from calcium oxide found in limestone rocks, calcium oxychloride is produced, a substance that, by seeping into the texture of the asphalt, causes it to crack.

A group of scientists from Drexel University, Philadelphia, United States, have investigated and tested a laboratory strain of the bacterium Sporosarcina pasteurii, a microorganism used in calcium carbonate precipitation processes, a natural cement.

These bacteria interact with common salt, as it falls within their group of nutrients, such that, in the process, they generate calcium carbonate.

Over the 28 days the study lasted, the scientists observed that the samples collected not only showed a lower amount of salt, but also that no deterioration had occurred in them and that, at the same time, the amount of calcium carbonate in them had increased.

In this way, in addition to preventing the degradation of road asphalt, the natural action of the bacteria would promote the resistance of the pavement.

On the other hand, the presence of the bacterial microorganism poses no risk to human health or to other living beings in the environment near the roadway where they may be, since they are non-pathogenic agents, so their application to asphalt would only bring benefits for the preservation and even partial regeneration of roads.