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ToadJones (Structural) (OP)
12 May 10 11:58
Does anyone out there have any information on monitoring the temperatures on a mass concrete pour using a thermocouple?
 
dik (Structural)
12 May 10 13:54
from my General Notes...


MASS CONCRETE

CONCRETE POURS HAVING A TOTAL VOLUME IN EXCESS OF 5 CU-M AND A MINIMUM DIMENSION IN EXCESS OF 3 FT SHALL BE CONSIDERED AS MASS CONCRETE

CONCRETE WORK SHALL COMPLY WITH THE RECOMMENDATIONS OF ACI COMMITTEE 207

CEMENT TYPE FOR MASS CONCRETE SHALL BE TYPE LH UNLESS APPROVED BY THE  [CONSULTANT | ENGINEER]

MAXIMUM AGGREGATE SIZE SHALL BE 2" UNLESS APPROVED BY THE  [CONSULTANT | ENGINEER]

PROVIDE PAIRS OF THERMOCOUPLES IN THE CENTRE OF MASS OF THE CONCRETE POUR

PROVIDE SURFACE THERMOCOUPLE PAIRS AT THE TOP SURFACE OF THE CONCRETE POUR DIRECTLY ABOVE THE THERMOCOUPLE PAIR AT THE CENTRE OF MASS, NEAR THE CENTRE OF TWO ADJACENT VERTICAL FACES AND AT ONE CORNER (5 SURFACE PAIRS TOTAL)

SURFACE THERMOCOUPLE PAIRS SHALL BE PLACED 2" FROM THE OUTSIDE SURFACE AND AT MID DEPTH OF THE CONCRETE POUR

THERMOCOUPLE PAIRS SHALL BE SEPARATED BY A DISTANCE OF APPROX 4'

MAXIMUM TEMPERATURE AT THE CENTRE OF MASS SHALL NOT EXCEED 50%%DC

MAXIMUM TEMPERATURE DIFFERENTIAL BETWEEN THE CENTRE OF MASS AND THE CONCRETE SURFACE SHALL NOT EXCEED 25%%DC

CONTRACTOR SHALL PROVIDE A PROCEDURE OUTLINING PROPOSED METHOD FOR MAINTAINING TEMPERATURE REQUIREMENTS FOR REVIEW BY THE [CONSULTANT | ENGINEER]

 
ToadJones (Structural) (OP)
12 May 10 14:09
Dik-
good stuff.
What is "%DC"?

Does any old thermocouple wire work?  
dik (Structural)
12 May 10 14:48
They have thermocouple wire already 'pre-fabbed'... the %%DC is for Autocad %%D yielding a 'degree' symbol and the C for Celcius...

You need to talk to someone about logging the information... most test agencies have this type of equipment.  Unfortunately, for the project I did the notes up for, they testing agency hadn't a clue about what they were measuring.

Dik
ToadJones (Structural) (OP)
12 May 10 15:24
Yes.
I realize that now....I use ALT+0186 to make a º symbol.

We are purchasing the logging device ourselves and monitoring our own pours.

 
dik (Structural)
12 May 10 21:46
Good... I know where I can borrow one <G>...

Since I've been with my present employer (2 years), they have purchased a laser distance measureing device (Hilti), a temperature measuring device (Laser pointer type) and temperature and humidity data logging devices... I had these prior to starting with them and they have found them so useful.  I still have a laser level (also Hilti) and a 5 sec theodolite (70 years old and mint).

We don't have thermocouples or logging device (likely 8 channel) but we have enough electrical and electronic dudes that we could glue one together...

Dik
ToadJones (Structural) (OP)
13 May 10 9:22
Dik-
As long as I can figure out how to do this, we figure it is better to spend some money to the equipment rather than pay a testing company...at least this way we have the equipment to show for it. The stuff really isn't too expensive relative to the projects.
It sounds like you just literally hook the thermocouple wires to the data logger and let 'er rip.  
dik (Structural)
13 May 10 13:46
That's about it... Good luck.

Dik
ToadJones (Structural) (OP)
13 May 10 14:34
Dik-
Can I blame you if it doesnt work?  
dik (Structural)
13 May 10 15:23
No... but you can use me as an excuse...

Check your thermocouples before you cast the concrete... for continuity as well as function and correlation.  If this is OK, then there's no reason it shouldn't work.  If I get a chance, I'll talk to one of the electrical dudes here to see about the data logging stuff...

Dik
BigH (Geotechnical)
14 May 10 0:24
Calibrate your readout units as well.  We have some 10 of these on site and they all read different - about 1 to 2 degrees.  We have calibrated vs 40degC temp.  Be careful about protecting them - depending on the installation, vibration during placement have been known to cut the wiring.  Shouldn't happen but sometimes "... .... .. -" happens.
ToadJones (Structural) (OP)
14 May 10 8:46
BigH-
Is 1 or 2 degrees that big of a deal?
Will the unit come with instructions for calibrating?
We are purchasing the logger from Omega.  
dik (Structural)
14 May 10 9:15
Calibration is good... but the biggest concern is the temperature differential between the centre and the outside.  My experience has been with cold weather, and it is possible that hot weather can provide a concern also.  Only in the event of a problem is the calibration an issue... I wouldn't normally lose sleep over a couple of degrees, but, I do appreciate precision and care.

Dik
ToadJones (Structural) (OP)
2 Jun 10 15:58
Logger is running and providing output just the way some literature I have read on the subject says it should.   
dik (Structural)
2 Jun 10 16:03
Glad to hear.

Dik
BigH (Geotechnical)
2 Jun 10 18:33
ToadJones - normally I would say not - but we have, due to "thermal analyses" very stringent maximum temperatures of the concrete we are placing.  Designers worried about thermal cracking - due to a "new" analysis, the max temps dropped 2 degrees C.
ToadJones (Structural) (OP)
3 Jun 10 13:32
Dik-

The thing is really working well.  
ToadJones (Structural) (OP)
3 Jun 10 13:35
Big H-
We did calibrate the unit.
The thing that was throwing me off was apparently the logger itself creates some heat and reads a few degrees F higher than a probe left in the air nearby the unit. The mfg. assured me that this was normal.

THanks
dik (Structural)
3 Jun 10 22:30
Generally looking at relative temperatures... if both are off a couple of degrees, they're almost the same...

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