2  FM quick reads on asphalt

1. Asphalt Repair Strategies and Tactics


Common asphalt repairs include resealing the surface, sealing cracks, applying cold- and hot-mix patches to potholes, and applying skin patches. A hot patch is more permanent than a cold patch and might be necessary during cold weather to temporarily repair a hole in a road surface.

Workers can make cold-mix patches by sweeping up loose rubble, using compressed air to blow away residual materials, applying a primer, and pouring the cold mix from bags into the hole. The final step is tamping with a hand tamper, air-powered tamper, or gas-powered vibrating tamper. The thicker the patch, the more compaction passes are needed.

Because hot-mix patches are intended to be more permanent than cold-mix patches, they tend to require more preparation work.

First, the worker must dig out the hole with pick and shovel or air-operated pavement breaker to square the sides and bottom to a uniform depth of at least 5 inches. Gravel is replaced to bring the depth to 3 inches and tamped using a hand or power tamper. The hot-mix asphalt fills the top 3 inches. The worker then rakes the patch evenly to 1 inch higher than the adjacent pavement.

The next step is to tamp the asphalt with a hand or powered tamper or roller to a level slightly higher than the adjacent pavement. This allows for further compaction by traffic without creating a depression, which can collect water.

Where alligatoring affects large surface areas or fine cracks cover large areas, one proven remedy is a skin patch. One to three workers can apply a sealer coat to the area after cleaning all loose rubble from the surface. Next, they apply a 1-inch-thick layer of hot-mix asphalt and rake it out evenly with a wide asphalt rake. Next, they tamp the hot-mix surface using a powered roller to ensure good compaction. Skin patches are appropriate only when the base is solid and properly graded for water runoff.


2.  Concrete and Asphalt: Effective Maintenance

I'm Dan Hounsell, editor of Maintenance Solutions magazine. Today's topic is, effective concrete and asphalt maintenance.

Exterior concrete and asphalt surfaces create a visitor's first impression of a facility. If drives, parking lots, and sidewalks deteriorate because they are not maintained properly, they can create problems that include poor appearance, tripping hazards, and costly repairs.

The causes of concrete and asphalt problems generally fall into three categories: design, use, and maintenance.

Design problems result from errors in material makeup, the placement of reinforcing materials, and poor support structure. One common design problem is excess water in the concrete mix. Managers need to properly specify concrete and asphalt mixes for each application and inspect them during application to ensure workers take test specimens and place the materials properly.

Another common problem is surface spalling, which results from imbedded metal around windows and other locations that strengthens concrete. Structural settling causes cracks that allow water intrusion, freezing and more cracking.

Even properly applied asphalt can develop problems that result from the effects of ultraviolet rays, water, petroleum products, and traffic. New asphalt combines asphalt-cement binder, sand and stone, and it is black. As the surface dries, asphalt turns gray from the absence of binder, and the elements begin to deteriorate it.

Managers also must be aware of unintended traffic, which can lead to premature degradation. For example, parking lots feature lanes for cars and those for trucks, which have much thicker bases.

If the design does not provide truck lanes or if trucks wander off designated lanes, they will crush the car-parking surfaces. The resulting depressions will collect standing water, and the water will turn to ice. Cracking and spalling can occur, causing damage that requires major repairs.


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