570.2 Joint and Crack Maintenance
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| Sealing Cracks, Joints and Edge Cracks |
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Contents
570.2.1 Filling and Sealing
Joints and cracks opened sufficiently (1/8" or more) to allow pouring should be filled or sealed to exclude foreign matter and prevent spalling, preserve the original filler and provide a smooth riding surface. Expansion joints require special treatment. Sawed contraction joints ordinarily are not to be poured unless the filler placed at the time of construction has completely deteriorated.
Pouring or sealing of cracks should be done in the latter part of the year when cracks have opened and temperatures are below 40 degrees F. It should be completed preferably before January 1, to exclude moisture for heavy winter snows. Work should not be done during extremely low temperatures, cutbacks should not be used when the pavement is wet and emulsions should not be used when the temperature is below freezing.
RC-800 or RC-3000 cutback asphalt or CRS-2 emulsified asphalt is used for the filler. Pouring is usually done with cone shaped pouring pots or with wands connected to a distributor. The temperature of the asphalt filler must be maintained to required temperatures and care exercised in pouring to hold the pouring to a minimum and minimize tracking of asphalt on to the centerline stripe. Blotting material, usually sawdust or sand, should be applied immediately to help prevent tracking. A box type bin mounted on the front end of a truck provides a convenient and safe source for filing individual sawdust or sand containers. The refilling of a bin from the supply truck should be done off the roadway. Where crack pouring is extensive and free sawdust is readily available a spreader truck may be used to spread sawdust.
Squeegees should be used to mop transverse joints on P.C.C. pavements that are subject to "D" cracking as this operation will prolong the life of the pavement. Mopping should start when the area adjacent to the transverse joints start to show extensive cracks and prior to spalling adjacent to the joints. The mopping operation will delay this spalling extending the life of the pavement. Liquid asphalt used in the mopping operation should be blotted with a light coating of fine cinders (wet bottom boiler slag) or sand.
Squeegees are not to be used on centerline, lane line, transverse except "D" cracked transverse joints, or random cracks. The only cracks where squeegees are to be used are widening cracks and "D" cracked transverse joints.
Care must be taken in using the squeegee to minimize tracking of asphalt onto the edge line. It should not be used continuously if it can be avoided. In areas where the widening cracks are not severe, the crack or cracks should be poured with normal pouring methods in order to reduce the loss of frictional resistance in a portion of the wheel track.
570.2.2 Edge Cracks
Edge cracks between ridge pavements and bituminous treated shoulders shall be filled and blotted with sand. The cracks should be checked several times yearly especially during the first year or two after construction and should be filled as needed to exclude water at all times. Any vegetation present in these cracks shall be treated with herbicide chemicals.
570.2.3 Sawed Joints
Sawed contraction joints may be sealed in the same manner as other contraction joints or cracks but only when the filler placed at the time of construction no longer seals the joint or when it has deteriorated so badly that foreign matter is admitted. Normally, sawed joints require very little sealing for years after construction but these should be checked annually for need.
570.2.4 Spalled Joints or Cracks
Joints or cracks which have become excessively spalled or open should be filled with a sand-asphalt mix, such as "Black Annie" or other fine graded mix. This should be done in conjunction with crack and joint pouring if of a minor nature. If the spalling is continuous at the center joint, it may be filled by using a small sled type hopper with a strike-off blade set high enough to allow for compaction. This spalled area should be thoroughly cleaned and lightly tacked and the material compacted thoroughly.
570.2.5 Removing Excess Joint Filler Material
Filler material extruding from joints and cracks to such an extent that it forms objectionable ridges and bumps and, in some cases, is being tracked, should be removed. This can be accomplished by cutting off the excess material with a motorgrader or by heating with a burner and scraping. Any material cut off must be removed from the pavement and traffic should not be allowed to pack the cuttings down after cutting with a motorgrader. Extruded expansion material in concrete medians, which is unsightly in appearance, can be scraped off with straight hoes.
570.2.6 Expansion Joints
Expansion joints such as those placed at bridge approaches to allow for expansion or to prevent "blow-ups" should never be filled with patching or mat material. Use a mixture of cutback asphalt and sawdust, tamp thoroughly to within 1" of the top and fill the remainder with a sand-asphalt mix. These joints must be checked closely and cleaned and refilled as necessary to allow for expansion and to provide a smooth riding surface. Expansion joints should be cut when temperatures are cool and as straight vertically and horizontally as possible. These cuts should be made with a concrete saw if available. In some cases it may be necessary to cut more than one expansion joint at bridge approaches to relieve the stress. If necessary, the joints should be cut approximately 50 and 100 ft. from the end of the bridge and should not be wider than 3 in.
570.2.7 Experimental Joints
Test joints filled with pre-molded rubber joint material or other types of joints constructed for experimental purposes shall be checked periodically and failures reported to the Maintenance Division. These joints should not be poured or repaired without approval of the Maintenance Division, with the concurrence of Research.
520.2.8 Metal Center Strip
Metal center strip that has deteriorated to the point where it becomes a hazard should be removed. All the metal strip including the vertical portions and the necessary concrete should be removed with air hammer chisels and the resultant V-shaped trench filled with a sand-asphalt mix or other fine graded high type mix. The area to be filled must be cleaned with compressed air, primed lightly, and the mix compacted thoroughly with air tempers. If not compacted thoroughly, the resultant settlement or hump will be a hazard to traffic.
520.2.9 Spot Seal Coating
Spot seal coating consists of sealing lean, oxidized, or map cracked areas small in size. If spot sealing cannot be controlled to a maximum of 10 percent per mile of the roadway surface on each mile at any one time, other means of repair should be considered.
Spot sealing is considered preventive maintenance and should be done before the oxidized or cracked areas deteriorate further. It should be done during hot weather, preferably the summer and early fall months, from May 15 to September 15.
CRS-2 emulsified asphalt is normally used. The asphalt is applied with a hand spray or distributor dependent on the actual and contemplated size of failure. Experience determined which method is the most economical and practical. Normally the hand spray method is only practical when the failures are small spot failures and not progressive. The asphalt is applied at an average rate of .35 gal/yd2, but control is difficult and the amount should be just sufficient to embed the aggregate enough to hold. Excessive asphalt will cause subsequent bleeding especially if the work is being done in cold weather.
The placement of cover aggregate should immediately follow the application of asphalt and be spread at the rate of 25 to 30 pounds/yd2. On all work, the amount should be controlled closely to prevent waste. It may be spread by hand, tailgating from a truck, or by a mechanical spreader. All areas shall be rolled immediately with a steel drum roller. Where the template of the road is poor rolling should also be done with a loaded truck. Rolling should be continued until the aggregate is firmly embedded. Cover aggregate should not exceed 1/2 in. maximum size for warm weather, and 1/4 in. maximum for cooler weather, unless the treated areas is such that larger aggregate can be embedded firmly to provide for more stability. On higher type surfaces, the aggregate must meet specifications for seal coat aggregate. Crush creek gravel may be used only if no other cover aggregate is available. If used, a minimum amount should be applied and additional rolling performed to embed such aggregate firmly. Brooming should be kept to an absolute minimum and any brooming done should be done lightly.
If the areas sealed lose their cover aggregate, additional aggregate should be applied and the areas rolled well. If the aggregate will not embed, sharp, clean sand should be applied and rolled wall to check the bleeding.
Proper traffic control, flagging and signing must be used on spot sealing operations to assure the safety of the public and our crews, and to minimize the whipping off of aggregate by traffic.
