Any paving contractor knows that you need to pay close attention to asphalt’s temperature while it is being installed, or undergoing repairs. There are a few different aspects of the asphalt’s temperature that you need to keep in mind in particular. Keeping these at the right temperature will improve asphalt’s strength, required maintenance, life span, and resistance to weather.
What happens when the temperature is off?
The ideal range for asphalt is 290-220 degrees F. When applied to the job site, it should be in the 275-300 degrees range. This ensures that it doesn’t become too cool while being laid to prevent compaction. Ambient temperatures, below 50 degrees will ensure it is too cold to fully compact. Some companies, however are able to lay thinner layers of asphalts at slightly cooler temperatures. But it is important to note that this is for a specific purpose: asphalt being laid in 1.5 inches or thinner, by companies with the right experience. Laying asphalt too thin can also cause problems, due to the layers cooling much more quickly than they would when laid in much larger quantities and thicknesses. As for general purposes though, go for 50 degrees minimum. 50 Makes for a pretty good bottom limit, as a rule, when it comes to asphalt laying temperatures.
What about the high range though? Usually anything over 90 degrees is considered too hot, and it will result in the asphalt melting, bruising, sloughing, and curing improperly.
Basically, the rule of thumb is this: keep it between 50 and 90 degrees. 40 Degrees is a good limit for a 1 and a half inches or less, 50 is a good limit for anything more, and always lay asphalt in sub-90 degree weather.
When the temperature is off, the asphalt will not be compacted enough and that prevents the aggregate from fully bonding with its surrounding pavement. This leads to nooks and crannies in the asphalt which allow in water. When water gets in, it expands and contracts with weather changes, starting the pothole and cracking process all over again. Additionally, when the asphalt cools too quickly, the entire surface will ravel. Raveling is asphalt deterioration through the loss of aggregate- the loose rocks and stones that compose most of the asphalt. You’ve probably noticed it when walking through a parking lot, and you start kicking around loose pebbles.
In the end, asphalt paving that is installed at the wrong temperatures will incur damage more quickly. This will shorten the entire life of the asphalt, and may create serious repair bills for the owner along the way.
What temperatures do you need to keep in mind?
Temperature of the asphalt mix itself
As we mentioned before, the asphalt mix temperature should be 275-300 degrees when it reaches the job site. This only becomes an issue when there is an extremely long travel period between the asphalt plant and the job site, allowing cooling during transit.
Temperature while it is being laid
As the asphalt is coming out of the paver, check its temperature with an IR thermometer. This ensures it is the right temperature during laying and compaction. It also makes sure that the environment isn’t changing the mix directly prior to application.
This is the temperature of the ground. Once asphalt is laid, it will start cooling to match the ground temperature quite quickly. Fortunately, the base temp is easy to monitor. Buy an infrared thermometer from any tool store, and check a few points in the areas the asphalt will be laid. Make sure it’s between 90 and 50 degrees, and you are good to go.
This basically means the weather. For the day of paving, check the forecast. We are going for that ideal condition with a high below 90 and a low above 50. Fortunately, that shouldn’t be too hard during large swathes of the year, particularly spring and autumn.
Check wind speed when you look at the forecast as well. The higher the wind velocity, the more quickly the asphalt will cool.
Also be on the lookout for precipitation, rain, sleet, or snow can stop your paving project in its tracks.
What seasons should you be careful of?
Summer and winter are the seasons to look out for. During both (even on milder days) the temperature can cause thermal segregation in hot mix asphalt. This essentially means that different parts have different temperatures. Thus, you will have the same problems mentioned above when the temperature isn’t right will occur.
Cold mix asphalt can be used at a wider temperature range
Cold mix asphalt uses special polymers in the aggregate bitumen mix. These polymers cause a chain reaction when it is laid, hardening the asphalt and bonding it to the surrounding surfaces.
Cold mix asphalt is applied at under 175 and 50 degrees Fahrenheit for construction.
When it comes to repairing damage, such as cracks and holes in asphalt paving, then cold mix asphalt works for all seasons. However, remember that cold mix is typically only used for temporary or smaller repairs.
Ensure your asphalt is installed in all the right ways
If keeping track of weather, ground, and mix temperature seems like a lot for your paving project, you aren’t alone. Fortunately, that’s why companies like Reliable Paving are here for you. Our team of over 200 asphalt paving contractors are professional, experienced (35 years plus!), and adaptable. Our services range widely, from repairs and re-striping to whole new paving installations. If you want to get your paving project started on the right foot, then don’t hesitate to contact us today.