Whitetopping
Encyclopedia
Whitetopping is the covering of an existing asphalt
pavement with a layer of Portland cement
concrete
. Whitetopping is divided into types depending on the thickness of the concrete layer and whether the layer is bonded to the asphalt substrate. Unbonded whitetopping, also called conventional whitetopping, uses concrete thicknesses of eight inches or more that is not bonded to the asphalt. Bonded whitetopping uses thicknesses of two to six inches bonded to the asphalt pavement and is divided into two types, thin and ultrathin. The bond is made by texturing the asphalt. Thin whitetopping uses a bonded layer of concrete that is four to six inches thick while an ultrathin layer is two to four inches thick. Ultrathin whitetopping is suitable for light duty uses, such as roads with low traffic volume, parking lot
s and small airport
s. Fiber reinforced concrete
is used in some thin whitetopping overlays and almost all ultrathin whitetopping overlays.
Whitetopping is suitable for asphalt pavement with little deterioration, although repairs can be made to the asphalt if necessary. If the pavement is badly damaged, it should be completely removed and a new concrete pavement should be installed. The pavement should be relatively hard, as well. Deterioration of overlays is significantly increased on asphalt bases with high viscosity
. If a grade or a distance between the pavement and a bridge
needs to be preserved, the asphalt can be milled so that the height of the pavement does not change. However, whitetopping requires the asphalt layer to be at least three inches thick. If necessary, a section of new concrete roadway can be placed under a bridge with gentle slopes on either side that meet up with the whitetopped portions of the road.
Asphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...
pavement with a layer of Portland cement
Portland cement
Portland cement is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout...
concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
. Whitetopping is divided into types depending on the thickness of the concrete layer and whether the layer is bonded to the asphalt substrate. Unbonded whitetopping, also called conventional whitetopping, uses concrete thicknesses of eight inches or more that is not bonded to the asphalt. Bonded whitetopping uses thicknesses of two to six inches bonded to the asphalt pavement and is divided into two types, thin and ultrathin. The bond is made by texturing the asphalt. Thin whitetopping uses a bonded layer of concrete that is four to six inches thick while an ultrathin layer is two to four inches thick. Ultrathin whitetopping is suitable for light duty uses, such as roads with low traffic volume, parking lot
Parking lot
A parking lot , also known as car lot, is a cleared area that is intended for parking vehicles. Usually, the term refers to a dedicated area that has been provided with a durable or semi-durable surface....
s and small airport
Airport
An airport is a location where aircraft such as fixed-wing aircraft, helicopters, and blimps take off and land. Aircraft may be stored or maintained at an airport...
s. Fiber reinforced concrete
Fiber reinforced concrete
Fiber-reinforced concrete is concrete containing fibrous material which increases its structural integrity. It contains short discrete fibers that are uniformly distributed and randomly oriented. Fibers include steel fibers, glass fibers, synthetic fibers and natural fibers...
is used in some thin whitetopping overlays and almost all ultrathin whitetopping overlays.
Whitetopping is suitable for asphalt pavement with little deterioration, although repairs can be made to the asphalt if necessary. If the pavement is badly damaged, it should be completely removed and a new concrete pavement should be installed. The pavement should be relatively hard, as well. Deterioration of overlays is significantly increased on asphalt bases with high viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
. If a grade or a distance between the pavement and a bridge
Bridge
A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle...
needs to be preserved, the asphalt can be milled so that the height of the pavement does not change. However, whitetopping requires the asphalt layer to be at least three inches thick. If necessary, a section of new concrete roadway can be placed under a bridge with gentle slopes on either side that meet up with the whitetopped portions of the road.