Message Board Thread - "Asphalt Paving "

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Asphalt Paving westie 5/4/2005
Does anyone know the emissivity of asphalt? I would like to attempt finding a condensate leak in a utility tunnel that crosses a street between two buildings. I would assume it needs to be done much the same as a roof inspection which I've done numerous times (i.e. an hour after sunset).

Thanks, Steve
Re:Asphalt Paving Gary Orlove 5/4/2005
What kind of asphalt mix is it? ;-)

Seriously, I would expect the emissivity of asphalt to be high normal to the surface; probably greater than 0.9. But I haven't measured its emissivity and with the infrared game, you don't know for sure until you actually do the measurement!

Gary Orlove
Infrared Training Center
Re:Asphalt Paving westie 5/4/2005
Actually it's whatever the City of Boston uses,I just found out I'll be looking for the outline of a cement conduit with building utilities running through it. I'll try .9 and see what comes of it. Thanks Gary, I'll let you know how it worked out when I'm there in June.

Re:Asphalt Paving JKEngineer 5/5/2005
If you are "looking" for something like conduit or a leak then you are dealing with an imaging application, not a measurement application. The emissivity will not matter. You are looking for anomalies or differences. Unless you are trying to quantify something, like energy loss, you will not be measuring temperature.
Jack M. Kleinfeld, P.E.
Kleinfeld Technical Services, Inc.
Infrared Thermography, Finite Element Analysis, Process Engineering

Bronx, NY 10463

866-884-6644 toll free
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Re:Asphalt Paving Greg at Stockton IR 5/11/2005

Jack Kleinfeld is correct. If it is as you say in a steam tunnel, just get in there and find it. If that is not possible, or it is a direct-bury line then get on a building or in an aircraft and look down. You should see something like the thermograph below.

Read more here...

Greg S.
Re:Asphalt Paving westie 6/1/2005

Thanks for the replies,I took images from the roof of a 4 story building and was quite successful in finding two leaks. I will post images at a later date.

Jack, did we take a training course at ITC? the name sounds familiar.

Again, Thanks for all your help.

Re:Asphalt Paving geologist 6/8/2005
You're looking for a delta-T. So while the emissivity of asphalt is about 0.95, the important factor is the empirical determination of the rate of differential cooling of the dry tunnel material and the wet stuff. The bigger the delta-T, the better the image. I would scan 1, 2, and 3 hours after sunset or 1, 2, and 3 hours after sunrise on nonrainy days. Probably the best source in the world for more guidance is the Washington State DOT in Olympia, WA. Ask for Kim Willoughby and tell her I sent ya. Attached is a pic of a Vermont asphalt highway at 93 degrees F ambient, midday. Best regards, Len Phillips

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