REPAIRING DEFECTIVE FLEXIBLE PAVEMENTS

Care and good judgment are necessary in applying suitable methods and in selection of proper materials for maintenance and repairs of bituminous surfaces. Both methods and materials vary considerably with local conditions, but the principles of bituminous work remain the same. The first step in making repairs is to determine the cause of the failure. Repairs must start at the source of the failure.

Removing Defective Flexible Pavement

The first step in removing a defective area is to mark out the area you want to remove. If you are going to use a pavement saw to cut the pavement, make your marks heavy and easy to use. The marks should be made with a waterproof material, such as paint or crayon, to prevent it from being washed off by the saw blade. The shape of the patch is important. If you expect the patch to be strong enough to support traffic, you must make the marked area square or rectangular in shape with two faces at right angles to the flow of traffic. By doing this, you will ensure the patch does not shove or corrugate when traffic flows over the top of it.

PAVEMENT CUTTING.- After you mark the area you want to remove, you are now ready to make your cuts along the marks. You can do this by using a pavement saw to make a fast, neat cut or by using a pneumatic hammer with a 5-inch asphalt cutting bit. When the pneumatic hammer is used, it leaves the edges

of the patch jagged. When making the cut with either tool, make sure the patch has square edges and is rectangular in shape. The cut should also extend at least a foot into the good pavement.

PAVEMENT REMOVAL.- After the outline cuts have been made, you can begin to breakup the defective material with a pneumatic hammer. Break the pavement into pieces that can be removed easily by hand. If the pieces are too large, a front-end loader maybe required to remove them. After the pavement has been broken up, the pieces can then be removed and hauled away (fig. 16-25).

After the pavement has been removed, check the condition of the base course material. When the base course is saturated with water, this material should be removed until you reach firm, dry soil. The sides should be vertical and the bottom as level as possible.

Base Course Replacement

After the hole is excavated, clean out all loose debris with hand brooms. When the hole is wet, it must be _{allowed to dry.} When the hole is deeper than the pavement, it should be filled with dense-graded aggregate. Fill and compact it in 2-inch lifts up to the lower edge of the pavement. On large patches, compaction can be done with a roller. Small patches must be hand-tamped. On large patches, the edges must be hand-tamped.

NOTE: Specification may require that a compaction test be performed on the base course before a prime coat application.

Figure 16-25.-Removing defective flexible pavement.

After the base course has passed the compaction test, prime the hole with a light application of asphalt, which can either be sprayed or brushed on. The prime material must be thin enough so that it can be applied lightly.

NOTE: An excess of asphalt prime coat will flush into the patch mix and causes bleeding.

The final step in the preparation of the hole is to apply a tack coat to the vertical faces, as shown in figure 16-26.