Asphalt Paving: Temperature and Timing
Asphalt Paving: Temperature and Timing
Most people are aware that asphalt is applied while it is quite hot, so it might seem that paving can be performed even in cold weather. However, it can actually be too cold to pave — there are certain laws of physics that simply cannot be overcome completely. For asphalt paving, the most important of these physical laws involves the transfer of heat.
Asphalt Paving: Temperature and Timing
Heat Transfer
When two materials having different temperatures contact each other, the hotter material will transfer its heat to the cooler material until the two materials are roughly the same temperature. This is referred to as conduction. However, heat can also be dissipated by convection; for example, a strong wind expedites the cooling process as long as the air temperature is less than the temperature of the material.
What This Means for Asphalt Paving
If asphalt pavement is to be durable, it must be well-compacted. Compaction reduces the air voids inside the pavement. Excessive air voids can reduce the pavement’s strength, make the pavement more prone to fatigue, increase raveling, decrease the pavement’s durability and lead to rutting. If the asphalt loses too much heat before it has been sufficiently compacted, it will be very difficult or even impossible to ensure that excess air voids have been eliminated.
To ensure that excessive heat is not transferred before compaction, contractors must monitor three temperatures. The first is the temperature of the asphalt mix when it is delivered to the site. The second is the air temperature, which should be a minimum of 50 degrees Fahrenheit and increasing throughout the job. The third is the temperature of the surface on which the asphalt will be installed. The surface temperature is extremely important; this is where the asphalt will lose a great deal of its heat through conduction. Typically, the surface temperature must be at least 50 degrees Fahrenheit, but this minimum may need to be adjusted for the mix and ambient temperatures as well as for the wind velocity.
Timing of Compaction
The exact timing depends on numerous factors. The three temperatures are important, but so are the size and shape of the aggregate in the mix, the properties of the asphalt binder and the thickness of the asphalt layer. For example, coarse and fine aggregates can require more effort to compact, high-viscosity binder can make the mix resist compaction and thin layers will cool faster than thick layers.
Timing also depends on the type and number of rollers available. Rolling equipment may have a different number of rollers, operate at different speeds or be more suitable for certain applications. On a large paving project, the contractor may form a train of rollers that could be different types; for example, he might use a roller with pneumatic tires in the lead position, a vibratory roller in the second position and a static steel-wheel roller in the third position. On a small project, the contractor may choose to use a single roller for all compaction work. An experienced contractor knows the advantages and disadvantages of the different types of rollers, so he will choose the roller or rollers that will provide the best results.
Choose Dirtworks for Quality Asphalt Paving
Dirtworks is an asphalt paving contractor in Cape Cod and we have been providing our customers with exceptional work for over 20 years. We are a family owned asphalt contractor offering an extensive line of services, including asphalt paving and overlays, asphalt repairs, parking lot striping, sealcoating and milling. We also offer site work and excavation services. Our customers in the Cape Cod area know that they can count on us for quality work — whether they need a road built, a parking lot constructed or a street repaired. To request a free estimate, call (508) 240-5541 or use the online form to send us your information.
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