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Asphalt & Slurry Seals

Asphalt Surfacing

The company has reliable equipment as well as back up from reputable supplies locally to be able to meet client needs. Depending on the temperature at which it is applied, asphalt is categorized as hot mix asphalt (HMA), warm mix asphalt, or cold mix asphalt. Hot mix asphalt is applied at temperatures over 300°F (150°C) with a free floating screed. Warm mix asphalt is applied at temperatures of 200–250°F (95–120°C), resulting in reduced energy usage and emissions of volatile organic compounds.Cold mix asphalt is often used on lower volume rural roads, where hot mix asphalt would cool too much on the long trip from the asphalt plant to the construction site.


Composite surfaces

Composite surfaces combine Portland cement concrete and asphalt. They are usually used to rehabilitate existing roadways rather than in new construction.

Asphalt overlays are sometimes laid over distressed concrete to restore a smooth wearing surface. A disadvantage of this method is that movement in the joints between the underlying concrete slabs, whether from thermal expansion and contraction, or from deflection of the concrete slabs from truck axle loads, usually cause cracks, called reflective cracks in the asphalt.

To decrease reflective cracking, concrete pavement is sometimes “cracked and seated.” A heavy weight is dropped on the concrete to induce cracking, then a heavy roller is used to seat the resultant pieces into the subbase. The theory is frequent small cracks will spread thermal stress over a wider area than infrequent large joints, reducing the stress on the overlying asphalt pavement.

Whitetopping uses Portland cement concrete to resurface a distressed asphalt road.


Gravel surface

Gravel road

Gravel is known to have been used extensively in the construction of roads by soldiers of the Roman Empire(see Roman road) but a limestone-surfaced road, thought to date back to the Bronze Age, has been found in Britain. Applying gravel, or “metalling,” has had two distinct usages in road surfacing. The term road metal refers to the broken stone or cinders used in the construction or repair of roads or railways, and is derived from the Latinmetallum, which means both “mine” and “quarry”.[19] The term originally referred to the process of creating a gravel roadway. The route of the roadway would first be dug down several feet and, depending on local conditions, French drains may or may not have been added. Next, large stones were placed and compacted, followed by successive layers of smaller stones, until the road surface was composed of small stones compacted into a hard, durable surface. “Road metal” later became the name of stone chippings mixed with tar to form the road surfacing material tarmac. A road of such material is called a “metalled road” in Britain, a “paved road” in Canada and the USA, or a “sealed road” in Australia and New Zealand.

A granular surface can be used with a traffic volume where the average annual daily traffic is 1,200 vehicles per day or less.There is some structural strength as the road surface combines a sub base and base and is topped with a double graded seal aggregate with emulsion.Besides the 4,929 kilometres (3,063 mi) of granular pavements maintained in Saskatchewan, over 90% of New Zealand roads are unbound granular pavement structures.

The decision whether to pave a gravel road or not often hinges on traffic volume. It has been found that maintenance costs for gravel roads often exceed the maintenance costs for paved or surface treated roads when traffic volumes exceed 200 vehicles per day.

Some communities are finding it makes sense to convert their low volume paved roads to aggregate surfaces.


Other surfaces

Pavers (or paviours), generally in the form of pre-cast concrete blocks, are often used for aesthetic purposes, or sometimes at port facilities that see long-duration pavement loading. Pavers are rarely used in areas that see high-speed vehicle traffic.

Brick, cobblestone, sett, and wood plank pavements were once common in urban areas throughout the world, but fell out of fashion in most countries, due to the high cost of labor required to lay and maintain them, and are typically only kept for historical or aesthetic reasons.[citation needed] In some countries, however, they are still common in local streets. Likewise, macadam and tarmac pavements can still sometimes be found buried underneath asphalt concrete or Portland cement concrete pavements, but are rarely constructed today.

It’s an engineered mixture of aggregate, or stones and sand, with liquid asphalt cement (a petroleum product). Varying sizes of aggregates are heated, then mixed, in exact proportions, with asphalt cement that has been liquefied at about 300°F. While the mixture is still hot, it is delivered to your driveway and paved on top of a base or sub-grade that has already been prepared. Very soon after paving, the mixture cools and hardens and you can drive on it right away.


Slurry Seals

Slurry Seal is a cold mix blend of high quality crushed aggregates, asphalt emulsion, water and mineral fillers, mixed together according to a pre-determined mix design from a laboratory.

It is applied to an existing surface, such as surface treatment or pavements, that are still in fair to good condition, as a means of a cost effective preventative maintenance. It reduces deterioration by sealing, prevents further oxidization, corrects raveling and provides or replaces a high degree of skid resistance. Slurry Seal is applied with a spreader box, which is connected to the slurry mixing unit.

The box is the width of a single lane, allowing a uniform spread of material in a single pass. Crews ahead of the unit set up traffic control, and sweep the surface before applying the slurry seal. Operators of the units monitor the mixing and application. After a short curing time traffic will be allowed to resume use of the freshly rehabilitated lane.

There are three types of Slurry seal commonly used, each using a different size of aggregate:

  • Type I - Slurry Seal (Fine Aggregate,1/8″ max) Used for lower traffic volumes and maximum crack penetration. Recommended application rates are 4.3-6.5 kg/m2
  • Type II -Slurry Seal ( General Aggregate,1/4″ max) Most commonly used slurry. Good for moderate to high volume roads. Recommended application rates are 6.5-10.8 kg/m2
  • Type III - Slurry Seal ( Coarse Aggregate ,3/8″) Used for high volume roads and heavier traffic. Recommended application rates are 9.8- 16.3 kg/m2

 

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