Photo from Unsplash

Originally Posted On: https://rstanleypaving.com/the-role-of-temperature-in-asphalt-paving/

The Role of Temperature in Asphalt Paving

If you’ve ever closely observed the pouring of new asphalt, you’ll notice it’s usually hot. That’s because the binder becomes sticky and pliable when heated, allowing the asphalt to spread easily and shape into place. If it were cold, it would be like trying to spread cold butter on a piece of toast.

Temperature is important in all aspects of your paving project. From the mixing process to the final compaction, maintaining optimal temperatures ensures proper workability, durability, and longevity of your surface.

In this blog, R. Stanley Paving LLC’s paving experts discuss the importance of temperature regulation for scheduling projects, selecting appropriate equipment, and achieving long-term results.

Understanding Temperature’s Impact on Asphalt Mix

Temperature acts like a conductor for asphalt’s paving performance. Hotter asphalt becomes stickier and more pliable, allowing for smooth spreading and compaction. This warm, flexible state is ideal for bonding the aggregate and binder together to create a strong final product.

There are a few important ways temperature can affect the properties of an asphalt mix:

Asphalt Viscosity

Asphalt and temperature have an inverse relationship when it comes to viscosity, a measure of flowability. As temperature rises, viscosity decreases, like a thick honey becoming a thin syrup.

This drop in viscosity makes the asphalt binder easier to work with. The hot, fluid binder allows for smoother mixing, spreading, and compaction during paving. Colder temperatures make asphalt stiffer.

Asphalt Compaction

Hotter asphalt mixes become softer and more pliable, allowing the individual particles to move and press together more effectively during rolling. This process eliminates air voids and creates a denser, more uniform pavement.

Colder temperatures make asphalt stiffer and harder to compact. This can leave air pockets trapped within the mix, creating spots prone to cracking and future deterioration under traffic or weather.

Asphalt Curing Time

Asphalt curing is a gradual process where the asphalt gains strength and flexibility. Temperature affects how quickly this occurs. Ideally, warmer ambient temperatures after installation accelerate the curing process by promoting the evaporation of lighter components and allowing the binder to solidify faster.

However, extremely high temperatures can be counterproductive, causing the asphalt to cool too rapidly and potentially hinder proper curing. Cold weather also slows down curing as the asphalt stiffens and chemical reactions proceed at a slower pace.

Temperature Control During Asphalt Transportation

Asphalt needs to arrive at your paving site within the optimal range for workability and compaction. This keeps your project running smoothly and avoids delays due to unusable material.

Here are a few key aspects:

• Heated tanks: Insulated tanks in transport trucks are equipped with heating systems to maintain the asphalt mix at a specific temperature throughout the journey to your site.
• Temperature monitoring: Sensors and gauges constantly monitor your asphalt temperature within the tanks, allowing for adjustments during transport if needed.
• Insulation: The tanks themselves are heavily insulated to minimize heat loss to the environment, especially during travel in colder weather.
• Scheduling: Haul distances and ambient temperatures are factored in to ensure the asphalt arrives within the desired temperature window. Longer journeys might require hotter asphalt.
• Additives: In some cases, additives can help the asphalt retain heat for longer durations during transport. Wax-based ones are common choices, as they retain heat effectively.

Effects of Ambient Temperature on Asphalt Installation

Ambient temperature refers to the surrounding air temperature at your paving site. It’s one aspect of paving that can’t be controlled; it can only be monitored and planned around accordingly. Still, it plays a role in the quality of the job.

Ideally, moderate temperatures (above 50°F or 10°C) are preferred. However, adjustments like using heated equipment to warm the base in colder temperatures or starting paving earlier in the day when temperatures are warmer can help extend the paving window.

During really hot summer days, shade, water sprays on the asphalt mix, or even nighttime paving can help keep your asphalt workable for a longer period. During the planning phase, selecting asphalt mixes designed for higher temperature tolerance can also be beneficial.

Cold Mix Asphalt: Purpose and Applications

Cold mix asphalt, unlike its more common counterpart, hot mix asphalt, is a pre-mixed asphalt solution that doesn’t require heating for installation. This can be convenient, but there’s a tradeoff: it’s far less durable.

Here are its key features:

• Composition: Cold mixes typically consist of three main ingredients-aggregate that provides structural strength, a binder that holds everything together, and special additives that allow the mix to stay workable at lower temperatures.
• No heating required: The key advantage of cold mixes is that they eliminate the need for heating equipment. The binder uses emulsions or cutbacks (solvent-based solutions) that remain workable at cold ambient temperatures.

Cold mix is ideal for quick repairs of potholes, cracks, or small damaged areas (roads, driveways, parking lots). It provides a temporary solution to prevent further damage until a more permanent hot mix repair can be scheduled.

Long-Term Performance of Asphalt Pavement Based on Temperature

If the temperature of your asphalt isn’t ideal for the ambient temperature conditions or surface, it might look good initially, but cracks will often appear shortly after it cools with enough traffic. An example would be if cold asphalt is laid on a hot summer day-it won’t integrate or become smooth.

Here’s how temperature during installation can affect long-term performance:

• Bonding and adhesion: Optimal temperatures ensure that the asphalt layers bond well with each other and with the underlying surface. Inadequate temperatures can lead to delamination or cracking as the pavement ages.
• Density and strength: Temperature affects the final density and strength of the asphalt pavement. If temperatures are too low, the asphalt may not achieve the required density, resulting in reduced strength and increased susceptibility to rutting or deformation.
• Resistance to cracking: Asphalt installed at incorrect temperatures may be prone to premature cracking. Proper temperature control during installation helps minimize thermal stresses and improves the pavement’s resistance to cracking caused by temperature fluctuations.

Achieve a Precise Asphalt Surface With Our Paving Expertise

Temperature control is critical in achieving a precise asphalt surface. R. Stanley Paving LLC’s paving experts control temperature throughout the installation process to ensure optimal compaction, durability, and performance.

Contact us today at (845) 831-1616 to discuss your next asphalt paving project!