Whitetopping is a construction process or strategy that calls for applying a layer of concrete to the surface of an existing section of asphalt pavement. The idea behind this particular process is to extend the life of the underlying asphalt and in some cases improve the outward appearance. There are various approaches to whitetopping, with some processes calling for bonding the concrete layer to the underlying asphalt while other methods do not require any bonding.
Typically, the bonding of whitetopping takes place with thicker applications of the overlay of concrete. Known as conventional or unbonded whitetopping, this approach is ideal for high traffic areas, such as streets or roads that experience a steady flow of traffic throughout a typical day. The bonding is actually accomplished by texturing the underlying asphalt before pouring the concrete, reducing the smoothness so that the concrete can partially seep into the asphalt surface. In contrast, bonded whitetopping normally requires the application of a thin layer of concrete to the underlying asphalt, making it ideal for situations in which relatively little traffic occurs.
In just about any setting, the process of whitetopping helps to protect and extend the life of the asphalt. Depending on the specific application, fiber-reinforced concrete may be used to provide additional strength the overlay. This is particularly effective when the strategy is used to add strength and durability to a section of asphalt that sees continual traffic and stress from one day to the next. Typically, different communities have building codes in place that help to determine how thick the concrete must be when used in certain applications. Local road contractors consult the codes before determining the type of concrete that will be used and deciding on the level of thickness necessary to create the desired level of protection.
As with any type of construction project, the proper execution of the whitetopping is essential to the success of the project. Failure to use the right type of cement or to mix the cement with the right aggregate and water combination may result in cracking, shrinkage, or other issues that render the concrete topping ineffectual. For this reason, it is not unusual for the aggregate to be prepared and measured with great care in relation to the cement that is also part of the concrete, and to also control the amount of water that is added to the mixture. In some cases, this involves washing the aggregate in order to remove impurities that could cause the concrete to crack or settle during or after the curing process.