Asphalt Pavement FAQ
Information about asphalt paving.
What is it? How it works? Which products?
What To Know
-
DescrA mix design is the asphalt pavement mixture design of rock, asphalt binder, and air.
The choice of which mix design to use will largely be dependent on the type of traffic and use it will receive.
Larger aggregate mixes will often do better with higher loads and thicker compacted mixes. Smaller aggregate mixes provide a smooth visually pleasing surface and are suited to thinner compacted thickness.
Light loads such as pedestrians and cars will be considered light and a smaller aggregate mixture is often preferrable. Sometimes this is called a driveway mix. This is the most common mix for pedestrian use, overlays, and skin patches.
Medium loads of light truck and higher volume light vehicles a typical 12mm to 19mm mix design is used. This is the most common mix design for patching.
Heavy loads as in commercial truck traffic and industry would require greater load dispersion and a larger aggregate use or combination of layers. 19mm plus aggregate sizes are common.
Most mix designs are done via the Marshall method in the lab which is tried and true. The Superpave method which is more sophisticated in design from the lab is customized to the site conditions and can have superior performance.iption text goes here
-
The compacted thickness of the asphalt is important to know and it will depend on the loading.
Asphalt is flexible by design and will move with the base preparation. Making asphalt thicker doesn't necessarily make it stronger. Thicker asphalt helps disperse loading over a larger area. A larger area of loading reduces deflection and shear failures. This larger load must be supported by the base gravels and sub-base or it will fail.
35mm is a minimum we suggest for any asphalt placed ontop of old asphalt.
50mm is a standard thickness to support pedestrians, lightweight cars.
65mm is a minimum for 1 ton pickups and RV's
75mm is a typical minimum thickness for commercial industrial yard, medium duty trucks, moderate traffic. Do not go thicker than 75mm without adding another layer.
80mm is placed in two lifts and is closer to a road design.
100mm is a two lift (layer) system used for high volume commercial, industrial, heavy duty vehicles, and roadways.
-
Asphalt paving should be done when the temperature of the ground is at 10 degrees and higher.
The ground should NOT be frozen.
Moisture should not be present on overlays. There can be some moisture when paving on a gravel base but runoff (flowing) water and anything more than light rain is going to degrade the product performance.
Hot weather will extend curing times and therefore associated closure times.
-
Best times are Monday to Friday during noise bylaw permitting hours.
Best seasons are April to October.
-
The lifespan of asphalt pavement is highly dependent on the traffic loading, volume, exposure, and water content int he soil.
Generally speaking, with proper maintenance, asphalt pavement can last up to 30 years. High traffic volumes and loads can cut this in half to 15 years.
Patching repairs and overlays also have a shortened lifespan due to thermal movements and flexural properties of dissimilar asphalt pavements.
-
Asphalt pavement can be used almost immediately, but it depends on the conditions.
If pedestrians are using, it should cool enough to people and pets don't burn their feet.
Driving can be done immediately after compaction, but only if turning isn't happening. Turning will cause marking. Large trucks can create heavy marking until the product has cooled.
As a safe rule, we like to see the asphalt cool overnight until opening the next morning.
Terms We Use
-
Saw cut, remove the old asphalt pavement, dispose of it off site and replace with new hot mix asphalt pavement.
-
Installing a new layer of asphalt pavement on top of an existing asphalt surface.
-
Placing smaller aggregate asphalt pavement on top of existing asphalt pavement and placing thin to feather edge.
-
A slow set asphalt adhesive that helps bond and seal new asphalt pavement to an existing surface.
-
MMCD stands for the Master Municipal Construction Documents. It is a common guide to paving developed by Cities and Municipalities in BC.
When ordering or specifying asphalt pavement types, sometimes we will use Upper Course 1 (UC1), Upper Course 2 (UC2), and Lower Course 1 (UC1). Upper course mix designs are generally finer, meaning they don't have larger aggregate in it. The finer the mix, the better it looks, but also generally the less capacity it has.
-
Milling or cold planing is the removal of asphalt pavement by grinding via carbide teeth.
Failure Description
-
When asphalt pavement is cracked into small sections often less than 1 sq.ft. in size. This provides a surface that has cracks like an alligator skin or reptile skin. aka Fatigue cracking, crocodile cracking. This failure indicates base repair may be needed.
-
Cracks that run the length of the asphalt pavement. These are generally cold joint cracks created from the paver during the paving process. They can occur due to thermal movements, moisture ingress, and shear failure. Sealant is often a suitable treatment.
-
Similar to longitudinal but run across the pavement in the shorter direction. These are often cause from thermal movement and shrinking of the asphalt pavement. Sealant is often a suitable treatment.
-
A combination of transverse and longitudinal cracking in large blocks. This is not similar to alligator cracking as the blocks are much bigger. These cracks can be sealer or asphalt pavement can be cut and replaced.
-
Cracks can be open or closed. Closed cracks indicate small cracks with little to no movement.
Closed cracks do not have enough movement to create much spalling and collect debris. Base failure may be possible but overloading, thermal stress, new cracks, and thin asphalt pavement thickness may also cause closed cracking.
Open cracks are large and show movement is common. Gravel base repair is often required to fix this situation.
-
Corrugations are a slight rippling effect of the asphalt pavement surface. This is an indicator of water movement underneath the asphalt pavement. Replacement of asphalt is a temporary fix until the water source is managed.
Caring For Asphalt Pavement
-
Seal coating is an asphalt coating placed on the surface of asphalt pavement. It's primary function is to add visual appeal to an asphalt surface to give it a new look. Seal coating when applied at the correct time can also help preserve asphalt pavement.
A sealcoat should be applied when the asphalt pavement isn't oxidized on the surface. This can be seen by the colour of the surface (grey is oxidized) and the roughness of the surface (sand missing indicates brittleness).
For maximum benefit apply a sealcoat between 6 months of new to 5 years old.
Sealcoats protect asphalt from oxidation. Oxidation of the asphalt binder removes flexibility of the asphalt leading to rough surfaces and cracking.
Sealcoating will not seal cracks or fix broken asphalt at all.
-
Gas and oil stains will damage your asphalt pavement. Once it is spilled, it is impossible to fully remove or clean it up. You can however minimize damage by removing or diluting whatever was spilled.
When oil and gas are spilled, absorb the product as best you can using a pourous absorbant material such as soil, kitty little, sand, etc. The material should be small enough to fall into voids in the asphalt. Vacuum clean up the absorbent material if it is not flammable. Sweep and remove the absorbant material. Wash the area. Use a light degreaser and biodegradeable product.
-
Crack sealing is the cheapest form of asphalt maintenance. Seal cracks as they appear, preferrably before the seasonal Fall rains. It is best to seal cracks when it is cooler as cracks will be open wider and less tension will be placed on the sealant when cold weather comes.
-
Asphalt pavement is slow to cool. Be mindful of barefoot traffic and pet feet on hot asphalt.
Driving straight on asphalt can be done within the hour. Turning may take 2 to 6 hours. Twisting of tires should wait until the asphalt surface has cooled below 50 C.
For best results, wait for asphalt to cool overnight before opening.
-
No. Salt does not damage asphalt pavement. Sand will scrub the surface and remove some of the fines of the asphalt pavement.
Do not use sand if the surface is sealcoated.
-
We recommend patching as soon as crack sealing is not a cost effective solution.
If an asphalt pavement is cracked to loose moving plates or missing asphalt, it is time to patch. If crack sealing is done at a density of greater than 3 lineal feet of crack sealing per square foot, it may be time to evaluate patching instead of sealing.
Asphalt Patching
-
Patching should encompass the failed asphalt area. This means to effectively patch an area for a longer duration, the patch should remove the failed asphalt area and the cracked area around it.
Water ingress is an accellerant to the deterioration of asphalt pavement. When driving over cracked asphalt that has allowed water to saturate the gravel base, the pressure of the tires moves the water in the gravel base displacing the gravel. For this reason we suggest removing an area slightly beyond the cracked section. Unfortunately, experience in asphalt patching will help recognize how far the pavement should be removed and replaced.
-
When asphalt is cracked and failing, you can place asphalt on top in some cases and only if it is placed with sufficient thickness. If the asphalt is cracked, it is almost always ineffective use of time and money to place a thin lift asphalt on top of it.
Roaron Construction recommends patching by placing asphalt on top of existing ONLY if there are depressions without cracking. Even at that, it would only be temporary unless the edges are ground down to tie in the new asphalt pavement.
-
Unless infrared heating is done to patch asphalt pavement, the edges of the patch will have a distinct cold joint. This distinct joint between the new and the old pavement will move differently due to temperature, will flex differently, and will transfer little load between the two. This will result in cracking along the edge of the patch over time, even with the best quality patching is done.
When removing asphalt patches, the existing asphalt and base gravel immediately adjacent to the new patch will be disturbed. This may cause a weak point in the old asphalt.
-
A remedy to the unavoidable problems with patching would be to crack seal. When a patch is complete, always place a crack sealant band around the edge of the patch. This crack sealant will act like tape or a bandaid to seal out water should a small crack start to form at the patch edge. This extra bit of work can add a minimum 1 year life to the patch.
Ensure a sufficient SS1 tack coat is placed on the edge of the patch prior to patching.
Ensure there is more than a minimum size of patch material to transfer load effectively. In some cases, too small of a patch will fail from overloading.
Ensure there is sufficient thickness in the patch. Sometimes the only reason asphalt fails is because of a thin spot. Replace with the correct thickness for known traffic loads.
-
Milling or grinding out a failed asphalt patch is sometimes an effective method of repair. Milling or grinding can remove asphalt pavement to create a proper tie in.
It is generally not suited to patching of loose asphalt, poorly cracked asphalt, or areas where patch geometry is important for aesthetics.
Only an experienced professional can assess milling options if traffic loading is known.
-
Infrared heating is patching by recycling the existing asphalt pavement through a reheat process. This process creates no cold joints, allows for cool / wet weather patching, has minimal site impact, and is generally quick.
It is not suitable for repairing oil damaged areas and has limitations of effectiveness on old oxidized asphalt.
Repairs of cracking can be done if the material is heated deep enough, but the quality is generally not as good as a removal and replacement patch. What you give up in quality you will usually save in pricing.
An experienced crew must run an infrared patching system with knowledge of rejuvenators, heating limits, and mix replacement.
Infrared patching will generally always require a rejuvenating agent or replacement of some mix in the patch to ensure a longer life repair.
DISCLAIMER
Not All Situations Are The Same
Information presented from this page are based from our experiences and knowledge. It is presented only as general information to assist in decision making and general procedures. This information may or may not provide accurate and/or appropriate solutions for any specific questions as each situation may vary and require different strategies. Use of the information provided does not hold Roaron Construction responsible for any liabilities, cost, wrong doing, or related expenses incurred from the use of information provided on this site.
Have unanswered questions?
Write us an email to get answers!
Check out our FAQ page for other information.