I was asked to determine if a pavement surface meets the specs which call for plus or minus 1/4" out of tolerance over 10 feet. As it turns out there are some scattered areas that exceed the tolerance by 1/16 and 1/8 inch.
Since the stated spec is to one significant figure does the 4 mean that they can have up to 1/4.5" or is it stone cold set at 0.250000 inches?
1/6" inch out of tolerance on asphalt paving sure isn't much--not even visible.
:good:
DDSM
IMHO since they gave a spec of +/- 1/4", I think it's 1/4".
Also, I think it is your duty to report the facts, not decide if it meets specs.
I have always viewed that type of spec as being an absolute as best as it can certified to by the inspector. If the inspection is done with a method with a plus or minus of a certain amount, then the spec should be expanded by that amount because the inspector cannot do better than that. A reading of the exact spec amount could be out by the inspectors plus or minus. Using a strict interpretation, the inspector would have to fall below the spec by their potential plus amount in order to say the contractor met spec. I do not believe that is the true intent.
> I was asked to determine if a pavement surface meets the specs which call for plus or minus 1/4" out of tolerance over 10 feet. As it turns out there are some scattered areas that exceed the tolerance by 1/16 and 1/8 inch.
>
> Since the stated spec is to one significant figure does the 4 mean that they can have up to 1/4.5" or is it stone cold set at 0.250000 inches?
>
> 1/6" inch out of tolerance on asphalt paving sure isn't much--not even visible.
IMHO, asbuilt the pavement to the nearest hundredth and leave it at that. Considering asphalt, your "stone cold set" sig figs seem way overkill.
> I was asked to determine if a pavement surface meets the specs which call for plus or minus 1/4" out of tolerance over 10 feet. As it turns out there are some scattered areas that exceed the tolerance by 1/16 and 1/8 inch.
>
> Since the stated spec is to one significant figure does the 4 mean that they can have up to 1/4.5" or is it stone cold set at 0.250000 inches?
>
> 1/6" inch out of tolerance on asphalt paving sure isn't much--not even visible.
- What are you using to measure? What is the slope of the pavement? Is there a State Regulation on the tolerance?
A total station to a prism would be hard pressed to provide vertical results much better than +/- 1/8" (0.01).
A level rod with 3/wire should produce vertical results to better then 0.01'.
Is this a straight edge spec, or profile-a-graph?
I would report the measurements to the significant figures relative to the precision of your measurements and allow your client to utilize the results as allowed by the contract.
Trying to report surface elevations on AC tighter than .01 is splitting hairs. When you start getting into thousandths of a foot you should be measuring something that will stick to a magnet.
They are requiring using of a perfectly straight 10-foot-long metal lightweight beam that is moved around to find the maximum difference. It is an asphalt paving job.
I was asked as a surveyor and civil engineer if it meets specs.
I agree. The owner is pondering getting them to remove and patch it because the asphalt paving smoothness exceeds tolerance by 0.01 feet approx.
Yes, that is an easy method of verifying a defect that you can already feel.
Sounds like it needs fixed..now it's about who pays.
Around here the state would require that a profile grinder be brought in, which would cost $40,000 min.
They are lucky if the agency is allowing a patch without a thin overlay or grinding.
AC is relatively inexpensive compared to grinding.
Per significant figures, I can lay a straight edge and a steel ruler down and visually see .03' vs. .02'
Take a picture and its done. If it's in excess of .02' and the agency doesn't like it...fix it.
Edit:
On DOT projects where they have strict profile-a-graph requirements, the bidders include some money for profile grinding.
Nearly every freeway job I see has some grinding...stop start issues.
Caltrans has a program of $ incentives based upon mat temps behind the paver.
To meet the spec, the contractor either has to incorporate a pick-up device that reheats the windrow or have a continous paving operation, which is extremely beneficial to ride quality and durability of the asphalt due to uniform compaction.
> I was asked to determine if a pavement surface meets the specs which call for plus or minus 1/4" out of tolerance over 10 feet. As it turns out there are some scattered areas that exceed the tolerance by 1/16 and 1/8 inch.
Well, if the scattered areas don't create bird baths, I would think that any rational owner would consider that patching the pavement surface may well create more problems in the future than it solves.
This sounds like a specification for which there should be some standardized test. Just out of curiosity, how are the limits of the area that is out of tolerance to be determined?
Ponding water is not the only consideration. Repetitive loading of 80,000 lb trucks will destroy the asphalt prematurely.
You are correct in that this should be spelled out clearly in the contract.
If the spec was lifted from some highway specification for grade control on pavements, surely then there is already an AASHTO test for compliance. One would argue, I think, that the spec was well known among pavement contractors and that the test was as well.
Yes, I agree
In my mind the question of what I report relates to what measurements I can repeat with a high degree of confidence. I would not want to report an area or spot as out of speck if I could not reproduce the measurement within the significant figures of my equipment and methodology. Application of professional judgment is always a part of the “art” of surveying. In short I agree with others, I think you report what you find; however be certain your number is accurate, not just precise.
The engineering textbook I use states fractions must be converted to thousandths in decimal form. So the conversion is you need to be within 0.021 feet. Outside of that is outside of spec.. So, you need to be using equipment and procedures that measure to the nearest thousandths of a foot, repeatable at whatever precision is in the spec.. Is a confidence level specified, such as sd or 95%, etc..
Oh, I see they specified the test, nevermind.
> The engineering textbook I use states fractions must be converted to thousandths in decimal form. So the conversion is you need to be within 0.021 feet. Outside of that is outside of spec.. So, you need to be using equipment and procedures that measure to the nearest thousandths of a foot, repeatable at whatever precision is in the spec.. Is a confidence level specified, such as sd or 95%, etc..
>
> Oh, I see they specified the test, nevermind.
Just what Duane said. Take the conservative view that anything beyond the decimal equivalent is exceeding the spec. Common sense dictates otherwise, as Kent said, if you try to fix something that isn't broke, you might break it.
What is that pavement for? Those are some really tight specs for asphalt. 5/8" was the limit on the airport taxiways we paved last fall but the smoothness straight edge was 16 feet. There were also allowances for a certain percentage to be out but not exceed a certain amount.
We have some really good asphalt crews and state of the art equipment but I'm not sure we could meet that spec. [sarcasm]Was it staked for paving on a ten foot grid? [/sarcasm]