While pavement appears solid and permanent, it is constantly moving below the surface. Temperature changes, weather events, and seasonal changes all cause asphalt and concrete to expand and contract. The small changes can cause pavement damage such as cracks and potholes; and despite the day-to-day minimal shifts, the months and years of shifting are what homeowners see when the asphalt of their driveway, a park pavement, or a road has visible damage.

Understanding why expansion and contraction occur is vital so that homeowners can understand their pavement damage and why preventative care is required. With maintenance and repairs, expansion and contraction damage can be curtailed before needing to rebuild it entirely.

Thermal Expansion Explained

When pavement materials are warmed, they expand—just like any other solid material. Asphalt and concrete have aggregates, sand and binding materials that react the same way to temperature. On a hot July afternoon, the surface temperature of a driveway or roadway can get above 120°F; so, the materials push outward a tad.

In fact, this outward movement is difficult to detect because it happens slowly. It doesn’t take a lot of outward movement to put stress on the material, especially when the pavement abuts an edge, curb or other hard surface. If this outward push is not able to move outside the perimeter of the pavement surfaces, the movement creates pressure that may cause small hairline cracks or surface buckling in the surface. With repeated small movements, the material eventually weakens.

Expansion is a natural process; however, if there are no joints, sealants, or intentional spacing when constructing pavement, the material has no point of release for the energy. That’s why engineers are careful to construct road construction with allowances for thermal expansion.

Seasonal Stress on Asphalt

Asphalt is a more flexible material than concrete, and therefore asphalt is the preferred material for parking lots, highways, and driveways. However, asphalt regularly faces the temperature gun, suffering from changes in temperature. During the winter months, cold air works to cool the material, making it shrink and contract. In the summer months, hot conditions expand the asphalt. Over time, all stable material will face fatigue under such movements.

Homeowners can observe and monitor for themselves how small cracks form through the winter and then are subsequently expanded once the weather warms. This will occur numerous times for all climates that see continuous and ongoing freezing and thawing cycles. When water soaks into the pavement, and then enters a freezing cycle and expands, the stress is magnified. This process continues until the pavement starts to become visibly damaged with signs such as spider cracks, and highs and lows.

• Asphalt is more susceptible in environments where the winter and summer extremes are high
• Freeze-thaw cycles exasperate cracking. Read more on this page.
• Additional weight from larger vehicles increases the wear of the material as it expands and shrinks

Activities like sealcoating and yearly inspections are by far the best and most economic ways to slow fatigue and annual seasonal wear. Adding a simple single layer of protective coating will give asphalt a coating of protection from the elements such as water (hydro) and sun.

Concrete vs. Asphalt Movement

Concrete and asphalt certainly serve similar intentions, but they work very differently when you consider expansion and contraction. Concrete tends to be less flexible and while it may not flex as easily, it exerts much weight when expanding. Sidewalks, driveways, and roadways made from concrete have control joints for a reason. These joints allow the concrete to move without breaking into pieces.

Asphalt is more flexible in nature. It moves slightly under weight, which prevents it from cracking immediately. That said, this has its downside too. Asphalt is very flexible and quite susceptible to fatigue when remaining any length of time under weight. Over time, asphalt can lose its strength of the aggregate binding product because of a worn binder from the aggregates from constant movement.

For the homeowner who needs to choose between asphalt and concrete, it is typically based on climate, proposed traffic, and maintenance habits. A reputable concrete contractor Nashville will help guide property owners down the right path based on local considerations and long-term needs.

Cracks From Temperature Cycles

Cracking (see https://www.britannica.com/technology/cracking-chemical-process for more info) is the most prominent indicator. It does not happen overnight and takes time. Pavement will expand and put pressure against surrounding structures and then contracts, leaving small voids to thermometer pressure change cause throughout the day. Each expansion and contraction cause weakness and allows tiny openings to water entry.

When moisture enters the pavement, it is a serious problem. The water will freeze in the winter, expands and forces the cracks open wider. When it rains, the rainwater will wash away (erode) the subbase layers, causing great damage too. Both processes will lead to potholes and uneven driving surfaces.

Professionals like driveway paving experts recommend sealing the cracks as soon as they develop. Performing small repairs early prevents large repairs down the road. Parking lot striping contractors stress the importance of filling cracks before painting new lines for the same reason, as they know broken pavement will not keep the paint in place once repeated vehicle traffic happens.

Preventative Care Methods

If you think you can escape the inevitable expansion and contraction of pavement, then you are wrong. You can, however, take care of your investment to prolong the life of your pavement. The difference between a surface that lasts decades versus one destroyed in a few short years is regular maintenance.

Some of the most effective preventative measures are:

• Sealcoating every other year or every third year as an effective barrier to UV rays and moisture
• Filling cracks when they are first discovered, to prevent water from entering and causing freeze-thaw stress on asphalt
• Good drainage design, to allow rain to drain away rather than allowing it to form puddles
• Professional inspections by driveway paving contractors or road construction professionals can notice potential issues before they spread

By utilizing the above preventative measures, homeowners can extend the life of pavement while being good stewards and promoting money-savings by preventing potential major repairs. Expansion and contraction never will cease, but smart preventative measures allow a safe, strong, and attractive surface we will all want, for many years.