Experience with ASTM C157 (Length change measurements of Concrete)

[SP777]

Wondering of anyone has experience with ASTM C157, and if so I would love to hear a simplified explanation. Here is a link to the standard for reference: ftp://ftp.ecn.purdue.edu/olek/PTanikela/To%20Prof.%20Olek/ASTM%20standards/Length%20Change%20C%20157.pdf

I have the molds, gage studs, reference bar and digital comparator. What confuses me is the de-molding process. I can see how I can get the specimen out of the main mold, however the two 3x3 steel plates holding the gage studs will still be attached to the removed specimen and I do not understand how to get those off. I'd assume if I oiled the inside of those 3x3 plates then I could just take them off by hand, but I do not want to disturb the gage studs.

Furthermore, I want to take a reading immediately after de-molding, then at 7 days and 28 days. I don't mind not following the standard to a tee.

Thanks

 

[conceng]

You will want to oil the molds to help in the stripping process. Once they are cast, make sure you clean off the top of the end plates well so hardened concrete doesn't impede the turning of the end plates. At 24-hours, strip the molds and carefully twist the end plates off the gauge studs (remember no righty tighty, only lefty lucy).

After marking the specimens, submerge them in a lime-saturated cure tank @ 73 +/- 3.5 for 1/2 hour to equalize the temperature in the specimen. Then take the initial, zero readings. Then put them back in the tank until 28-days, or otherwise specified. Once started drying, reading are typically taken as a minimum at 0, 4, 7, 14, 28-days and onward as described in ASTM C 157. We usually stop measuring at the specified age depending on the project.

Hope this helps.


Greg

 

[darthsoilsguy2]

lube the thread ends very well. Make sure the piece of the stud that is in concrete is completely clean. Don't screw the studs past finger-tight in the base plates. light oil the plate face without getting on studs... worked every time we've done it.

 

[SP777]

Guys, thanks so much for your input.

To follow up - I de-molded by unscrewing the threaded plates by hand. With a good oiling, it was no problem at all