With air temperatures last week in Minneapolis and Saint Paul reaching 40°F in January, and now a cold front sweeping in, we thought it would be appropriate to highlight some of the seasonal weather effects on asphalt pavements.

In winter, the biggest threat to asphalt pavements is the temperature. Minnesota winters can see minimum temperatures of -30°F or lower. Extreme low temperatures can cause asphalt to contract and shrink, and this contraction and shrinkage creates tension within the asphalt, meaning the asphalt is trying to pull away from itself. If this tension within the asphalt becomes too strong, cracks will develop in the pavement to relieve some of the tension. Rapidly decreasing temperatures cause the asphalt to contract quicker and build tension faster, leading to an increased chance of cracking.

Freezing temperatures also cause water that is trapped beneath the pavement to freeze. As the water freezes it expands and causes the ground to heave. This is commonly called frost heave and can occur below your pavement if it lacks proper maintenance and/or drainage.

In the spring (and sometimes in January), the winter snow and ice begins to melt. As the ice below the pavement (frost heave) melts, it saturates the soils beneath pavement. Also, the spring brings additional rain, which can puddle in deformed areas due to frost heave, and infiltrate cracks and seep beneath the pavement. Water is the biggest threat to asphalt pavements in the spring because it causes asphalt to deteriorate (very slowly). The longer asphalt is in contact with water, the more deterioration is likely to occur. This includes water puddling on top of asphalt, water flowing across asphalt pavements, water moving into the cracks of asphalt pavements, and water beneath asphalt pavements. This is why asphalt roads and parking lots are sloped to allow for quick drainage of the water. Protect your asphalt pavements by crack sealing as soon as cracks appear and patching potholes or severely cracked areas to prevent water infiltration.

During the summer, less rain and more sunshine means asphalt pavements are slowly deteriorated by oxidation. Oxidation is caused by exposure to UV radiation (sunlight) and it is the process of light oils in asphalt combining to form heavier oils. Additional heavy oils make the asphalt more brittle and more likely to crack and/or ravel.

Lastly, fall brings an increase in rainfall, and water becomes the biggest threat again (as in spring). Fall is also one of the busiest times of year for pavement construction, and rain is the biggest threat to delaying project completion.

For more than 70 years, BR has been striving to provide the highest quality asphalt pavements to our Minneapolis-St. Paul customers. We work towards this goal by continually increasing our knowledgeable about every aspect of asphalt pavements, especially how the changing seasons will affect them. For more information about Bituminous Roadways, asphalt maintenance, asphalt paving, asphalt materials, or to get an estimate, please contact Bituminous Roadways at (651) 686-7001 or visit our website.