Most people understand that two different materials will have different costs, but what about the time it takes to get the work done using each of those materials? For a business or resident who is impacted by the length of time it takes to rebuild a pavement, the duration of the project has an indirect cost to them. And that cost should be taken into account when deciding what type of material to use.
COMPARING ALL COSTs
Historically, asphalt is thought to be less expensive initially, but doesn’t last as long and requires more frequent maintenance and/or replacement. Concrete typically costs a little more up front but needs much less long-term maintenance and repair over its longer life span. The indirect costs those impacted by reconstruction due to delay or inconvenience are often referred to as user delay cost. There are ways to quantify this cost, but the methods can be complex and difficult to assess.
TIme TO BUILD EACH PAVEMENT
Asphalt is typically laid in layers around 1.5 to 2 inches thick. Therefore most asphalt driveways or parking lots require at least two applications to get the full thickness needed to support vehicle traffic. The first (base) layer of asphalt is usually not strong enough to allow high amounts of traffic for a longer period of time.
Concrete is placed in one full layer, usually anywhere from 4 to 8 inches (or thicker for highway and airport pavements). This means that concrete projects can have as little as half the actual construction time as asphalt, resulting in less disruption to drivers and residents.
Both concrete and asphalt require a cure time, although with asphalt the wait simply involves a cooling off period and is often achieved within a day. With concrete, the required curing time is dependent on the concrete mix and ambient temperatures. In the summer, light traffic (cars, SUVs and pickup trucks) can usually drive on the pavement after about two days, and heavy trucks or buses within three to five days. In the spring and fall, with cooler temperatures or with certain concrete mixes, the cure time could be anywhere from three to seven days.
WORTH THE WAIT
Let’s give a quick example of a 1,000 square foot residential driveway. If the asphalt base layer takes 1 hour to pave, it will require a few hours to cool before the top layer can be placed. This means the crew will likely come back the next day (Day 2) to finish up. And the driveway can start being used (with caution) on Day 3. With concrete, a good contractor can place the 1,000 square feet in about an hour. In the summer, the concrete should be strong enough to drive on after two days, meaning it can be opened on Day 3, with no difference in down time to residents. And with proper materials, construction, curing, and long-term care, your new concrete pavement should last almost a lifetime.