Bird Baths/Low Spots in AC Paving
Bird Baths/Low Spots in AC Paving
(OP)
Does anyone have a good method of quality control of "bird baths" or low spots in Asphalt Concrete Paving construction. I am supervising the construction of some roads, and have found some bird baths after the paving was already complete. I would like a method of either preventing it from happening, or quality control during paving and subsequent corrective measures. The spec calls for using water to flood the newly paved areas. However, this is not very practical in the field.





RE: Bird Baths/Low Spots in AC Paving
Leave the remedy of the problem now to the contractor.
RE: Bird Baths/Low Spots in AC Paving
However, just as a AC contractor will have a tack truck ready to go, he should also have a water truck ready to be used at the inspectors discretion especially if is written that way in the specs - which most state specs require contractors to aid the inspection team.
IMHO, the problem may be many-fold yet it seems likely to be a common problem associated with
1. Existing holes/swales in pavement that are not properly wedged prior to mainline paving
2. Too much horsing around with the paving machine controls
Good inspection will deal with both problems and should avoid costly removal work by the contractor later. Thus he should be glad that its pointed out before hand.
RE: Bird Baths/Low Spots in AC Paving
Flooding a pavement to check surface quality is absurd.
A common QA/QC criterion for surface profile is to have no more than a 1/4-inch variation in 10 feet. This is checked with a 10-foot straightedge in longitudinal, transverse, and diagonal directions. Milling and overlaying is the proper course of repair. "Skin" patches for birdbaths are not acceptable. Cut out and replace or mill and overlay.
QShake's comments are good as well. His experience is similar to mine.
RE: Bird Baths/Low Spots in AC Paving
For concrete paving a "profilograph" is used to determine the acceptable level of surfacing. It may be that this is also used in ACC pavement as well. Having a straight edge following the paver, luteman and roller is also a good idea.
RE: Bird Baths/Low Spots in AC Paving
RE: Bird Baths/Low Spots in AC Paving
Another problem location is when you have an overside drain at the bottom of a long sag parabolic vertical curve. These are difficult to find with a hand level. We usually put the dike in first, bring in the water truck, and pay extra work to saw out the dike at the low point. A little extra expense, but guaranteed to find the right place.
Charlie Sainte Claire
Caltrans
RE: Bird Baths/Low Spots in AC Paving
RE: Bird Baths/Low Spots in AC Paving
------------------------------------------
"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail."
Wm. Phelps Eno, ca. 1928
RE: Bird Baths/Low Spots in AC Paving
If you path only receives foot traffic or very light vehicles, then you might consider a skin patch using a very fine asphalt mix.
RE: Bird Baths/Low Spots in AC Paving
RE: Bird Baths/Low Spots in AC Paving
RE: Bird Baths/Low Spots in AC Paving
RE: Bird Baths/Low Spots in AC Paving
If you have to pave using several lifts of varying thickness and don't have any type of automatic controls, after each lift take shots on on what you just paved, then write down the fills on the pavement, then do your best to pave to those fills. As AC from behind the screed will compact down 20 to 25% after rolling,try to build up grades so that the final lift (pass) is a consistant thickness (so that the final lift compacts down the same amount). Then use a 12' straightedge with a carpenters level. When the mix is still hot and after the initial breakdown compaction, slide the straightedge/level up and down the flowline, find any high spots pound them out with the vibratory roller (before the ac cools).
RE: Bird Baths/Low Spots in AC Paving
Or you're rehabbing a road and can't adjust the grade much (e.g., a city street)
------------------------------------------
"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail."
Wm. Phelps Eno, ca. 1928
RE: Bird Baths/Low Spots in AC Paving
and you don't care about a few bird baths.
RE: Bird Baths/Low Spots in AC Paving
check the asbuilt for any slopes at or less than 2.0%
If you have a problem with the base, then correct prior to placing AC.