When it comes to paving an asphalt parking lot, environmental temperature can greatly affect the success of your project. If asphalt is paved in the wrong conditions, it will not set at the appropriate rate. This leads to a rough, rocky surface instead of a smooth, black lot. Worse still, the pavement will be more likely to retain water, compromising the asphalt’s integrity long-term. With this in mind, when is the best time of the year to pave an asphalt lot? When are you more likely to meet ideal temperature requirements (often referred to as “the goldilocks zone”)? Let’s find out.
Hot Mix Asphalt (HMA) Temperatures
Hot mixed asphalt is manufactured at temperatures between 275°F and 325°F. These temperatures can drop between 5°F and 25°F on the journey to the worksite depending on environmental conditions and distance travelled. Because of this, HMA temperatures should be between 270°F and 300°F upon arrival at the work site. If environmental temperatures are too low, the asphalt will cool too quickly and set up, making it very difficult to achieve the necessary compacted density. The thinner the layer of asphalt, the more this is exacerbated. Similarly, if HMA temperatures exceed these boundaries, it can damage the chemical and physical binding properties of the asphalt. It is important to measure environmental temperatures to ensure a successful paving day. There are two temperatures to measure: ambient (air) temperature and base (ground or existing pavement) temperature. Both have a significant effect on the paving process.
Ambient (Air) Temperatures
Monitoring the ambient temperatures is key to successful paving. You must be aware of the projected highs and lows for the day, the temperatures during work hours and the wind velocity/ wind chill. The normal requirement is that ambient temperatures should be a minimum 50°F and rising, factoring in wind chill.
Base (Ground) Temperatures
Ambient temperature affects the paving process, but base temperature is an even greater factor. Monitoring the existing temperature of the ground or existing pavement can be accomplished with an infrared thermometer. Like ambient temperatures, base temperatures should normally by at a minimum of 50°F and rising.
The thickness of the asphalt can affect the range of both ambient and base temperatures. Paving can occur at temperatures as low as 35°F if the asphalt layer is between 3″ and 4″ in thickness. That said, it is much more efficient to stay within this mid-range of temperatures. Colder temperatures limit the amount of time that work crews have to pave. For example, when paving asphalt 1.5″ thick at 40°F, crews only have 16 minutes to complete the work.
Though the work can be done at almost any time of year, paving in milder temperatures offers more scheduling flexibility and ensures that your asphalt lot will have integrity and longevity. In Indiana (and areas of a similar climate), this means that late spring and early fall are the optimal seasons to complete your paving project. If you’re commercial parking lot is in need of paving, now is the perfect time to contact us. We’d be happy to get the job done.