Definitions and Lifecycles of Surface Treatments
The existing infrastructure is totally removed due to its extensive deterioration, and is then replaced. When a road is reconstructed, typically other abutting infrastructure within the road allowance such as sidewalks, guardrails, and ditches are also reconstructed at the same time to take advantage of resources already deployed at the site, and in some cases, this also applies to subsurface infrastructure such as water/sewer mains and culverts.
A pulverization machine grinds the road surface along with a portion of the road base underneath, after which fresh gravel and resurfacing can take place. This method is typically used to replace highly deteriorated high float or asphalt roads where patching is no longer effective,
High Float (Hard Top)
High float is also known as hard top, tar-and-chip, and tar-and-stone. It is the application of one (single-surface treatment) or two (double-surface treatment) layers of an emulsion base (tar) overlaid with crushed limestone. This can be done on top of either a gravelled, pulverized, or existing hard top surface, and is usually put in place due to increased traffic volume or deteriorated existing hard top. Depending on traffic volume, it takes time for the limestone to settle and form a smoother surface – usually about 1 month for typical traffic volumes. Depending on many factors, the lifecycle of high float is typically about 5-7 years.
Micro-resurfacing is the application of a thin layer of an emulsion base overlaid with crushed limestone when a hard top road is beginning to deteriorate and allow water to seep into and under the road. Depending on the condition of the road and other factors, the surface is overlaid with 0.5 - 0.75 inches of material in order to seal the surface of the road, and extend its lifespan by 2-5 years. This type of resurfacing is very similar to slurry seal, which basically entails an application of an adhesive layer to the road in order to protect it from water penetration. As with high float, the limestone will require some time to settle into a smooth surface.
This is the everyday surface for most roads with very high volumes of traffic, such as county and arterial roads, and for all of the King’s Highways in Ontario. It is a petroleum-based mix of emulsion, adhesive, and aggregates such as sand and gravel, forming a relatively smooth roadway surface once applied and rolled onto a gravel base. Asphalt is much more durable, but much more expensive, than high float, and is more common in urbanized areas than in rural areas. It is typically 2-4 inches thick, and depending on many factors, has an expected lifespan of about 10-15 years.
Even though gravel roads tend to receive lighter traffic volumes than hard-surfaced roads, they do require re-graveling of about 3-4 inches of A-gravel about every 3-5 years, depending on many factors such as traffic, soil conditions, and quality of the existing gravel base. Gravel roads tend to lose a layer during the winter from snow plowing, and also gradually lose depth from weathering and movement of traffic all year round.