presented by McDonald Paving of Spokane

The roadway has remained paramount in the United States of America since the time of its independence, with the issue of road building serving as a hot political topic as far back as the time of John Adams and Thomas Jefferson. The development of private roads, known as turnpikes, formed the backbone of the U.S. roadway system throughout the early 19th century. Paving the roads remained a major expense in the early days of the republic, so turnpike companies often resorted to the creation of plank roads, which used wooden planks to minimize rolling resistance for carriages and kept them from getting stuck in the mud after a wet weather period.

The first major technological advance in paving roads in the United States came from Scotland and caught on around 1820. Engineer John Loudon McAdam developed the technique of road building that would be named for him by combining aggregate materials such as stone and gravel and compacting them with a roller. The small aggregate stones allowed for the iron carriage tires of the time to travel smoothly. By the 1830s, many of America’s roads had undergone macadamization using the combination of stone dust and water as a binding agent, creating what is known as water-bound macadam.

While this process served the horse and carriage of the 19th century well, the fast speed of the motor vehicle created dust clouds on macadamized roads. To solve this problem, engineers used tar as a binding agent, creating what they called tar-bound macadam. U.S. engineer Edgar Purnell Hooley later developed a road-surface mixture of ironworks slag and coal tar, called tarmac, which proved to be more resilient. Finally, the use of bitumen as a binding agent allowed for the development of asphalt concrete. Road pavers around the world, including McDonald Paving of Spokane, continue to use asphalt concrete as a primary construction material today.

While paving and other roadwork remain a primary form of business for us at McDonald Paving of Spokane, we also help businesses and homes in preserving their pavement with sealcoating. Sealcoating serves as barrier coat for asphalt concrete surfaces, a minor yet useful measure in maintaining a strong, lasting driveway or parking lot. It protects pavement from the ultraviolet rays of the sun and the oxidizing effects of wind and water by providing a membrane that limits asphalt oxidation and water seepage. Pavement also benefits from sealcoating by gaining increased texture and thus surface friction, making it less slippery, especially in the rain.

Sealcoating primarily uses two different emulsifiers. The most common emulsion material is refined coal tar, which contains very stable closed-ring aromatic compounds as its chemical base. Refined coal tar’s popularity comes from its resilience to destructive elements like the weather and oily substances. In recent years, another acceptable option for sealcoating has come from using asphalt as an emulsion material. While not resistant to oily substances, asphalt emulsion sealcoating still helps maintain the pavement’s surface integrity and carries the benefits of easier application, a weaker odor, and less skin irritation than refined coal tar sealcoating.

Because sealcoating best serves pavements in sound condition, the ideal candidate to benefit from the process possesses low to moderate cracking and raveling as well as low friction numbers. Before sealcoating can begin, the coater must clear the area of debris, fill and repair any cracks as necessary, and clean any oily substances from the pavement to be coated. Then, the coater must mix the sealant, supplied in concentrates, with water, silica sand, and additives to dilute it and ensure proper consistency during application, keeping in mind humidity and the amount of future traffic the pavement will face. Finally, the coater can spray the sealcoating over the pavement, preferably in two coats to maintain a high level of protection. After undergoing a drying period of 8 to 24 hours, the pavement will be ready for use.