Concrete Cylinders ends - cut, grind, or cap? 1

[Eapnat]

We are having a office debate on what the "best" way is to get the ends of our cylinders in tolerance before conducting compression testing. We handle roughly 400 cylinders per year. Currently they either do nothing or use a hand grinder. I would like to drag them to the right way.
I'm trying to get a feel for industry standard.

secondly,
what tools/setups are being used (so I'll know what sort of investment we are talking about)

Thanks much!

 

[Eapnat]

To further clarify, with the grinding or cutting we would be using unbonded caps with neoprene pads; by capped I mean sulfur.

 

[Ron]

First of all, you have a standard to meet. In your case, ASTM C172, C31 and C39.

With regard to C39, the proper way to achieve planeness is to trim the cylinder with a diamond blade or an abrasive blade. Abrasive blades tend to bend and be less accurate than diamond blades. Hand held grinders should NEVER be used.

If you are having planeness issues with your cylinders, check first with the fabrication of the cylinder...are your technicians properly trained? Do they use proper equipment? Do they understand the need to finish the top of the cylinder as accurately as practicable? Teach them to finish the top of the cylinder as if it were a critical floor slab...flat and smooth.

Your volume of cylinders is quite low. My experience has been more on the order of several hundred per week. With that volume, you should not have an issue with planeness, as they can be properly fabricated or trimmed if not in compliance with C39 planeness requirements.

If you ever get into a litigation situation, you'll be grilled on your techniques. Make sure they comply with the standards...otherwise, you might have some liability issues.

 

[BigH]

Ron - we were breaking 200 per day a few months back . . . We use sulfur capping although the contractor is also using neoprene capping for higher strength concrete

 

[Ron]

BigH...geez, that's a concrete breaking factory! We were doing about 80 per day at one time, all with sulphur caps. Went to neoprene caps much later, and still did correlations.

 

[Eapnat]

Thank you for the information. I'm having to drag them kicking and screaming ("heck we're been doing it this way for 20 years, why do we need to change?") to the right path.

I laid it out plainly and told them that if we did not conduct our testing per the specs then our results were not defendable (thus useless); do it right or don't do it because its not worth the liability.

Here's to getting them on the right track.

Does anyone have a saw recommendation?

 

[Ron]

Here are links to several manufacturers/suppliers. I would get a 20-inch saw...that way you can cut a cylinder lengthwise for petrographic or microscopic examination. A 14 inch saw will do the job (barely).

http://www.contractorsdirect.com/Concrete-Tools/Masonry-Block-Saws/Multiquip-Trak-14-Masonry-Saw

http://www.contractorsdirect.com/Concrete-Tools/Masonry-Block-Saws/MK-5005-Masonry-Saw

http://www.edcoinc.com/masonry-saws-ms-20.html

http://constructioncomplete.com/Catalog/Paver-Block-Saws/IMER-Blockhead-500-20-Masonry-Saw

 

[BigH]

Ron - placing up to 25,000 m3/month; cylinders every 100 m3 - some placements were 1200 to 1400 m3. 7,28,56 and 90 day strengths required. Finally contractor got a good machine and we didn't have to do his . . .

 

[Ron]

BigH...that's a lot of concrete. You could recycle the cylinders for roadway base material!

 

[msucog]

i will say that it's amazing how many firms have complete disregard for standards. i'm glad to see eapnat working to improve their operation. and you're not alone eapnat...i will say there are many other really screwed things that go down at a lot of firms...no wonder there's firms lowballing work (they have no control whatsoever over their testing, quality or otherwise). as a professional, i tip my hat to anyone that goes against the grain to do things in the spirit of doing it right. the status of the industry is rather miserable at the moment when it comes to doing things right.

i'm buying a saw in the next month so i'll try to pass along any info i can. if you'd like, shoot an email to my g mail account using my username and i'll shoot one back.

and i've been away for a while but glad to see bigh and ron (and others) are still around helping all of us be a little wiser.

 

[Ron]

msucog...I was wondering about you!! Glad you're back and contributing as always.

 

[msucog]

been "busy" lots of crazy interesting stuff...and using a lot the info all you old pros have passed along to my young butt (so "thanks!" to all of you). will be much busier going forward too...taking CA PE soon then GE on top of everything else. [fingers crossed]

back to the topic on a semi-related topic: for you guys that don't use sulfur cement, what is your preferred gypsum/cement type capping compound (name brand please)? i've played around with a few but am not completely satisfied. compressive strength is fine and haven't had any performance issues as far as i can tell but am trying to find something easy to find, works well, sets in a reasonable amount of time and satisfies asmt. would a non-shrink cement grout from the local hardware store work while satisfying astm? all i've ever used is sulphur but i'm trying to stay away from sulfur due to the whole ventilation & safety related issues...plus it smells like hell and i don't think the nearby tenants at the new place would appreciate it.

 

[Ron]

Hydrocal is a gypsum cement that works for capping, but the problem with most gypsum cement products is that you can't get high enough strength out of the caps.

Yeah, sulphur is a bit pungent...but smells like money in our business!!

You can use a "neat cement" paste, but you'll have to cast it when you first start curing the cylinders and then be careful not to break the caps.

I would go with neoprene caps and sulphur correlation.

 

[msucog]

thanks ron. i'm going neoprene but want to have a plan in place in case i need it. i have run across hydrocal but don't have much experience...i'll do some correlations and keep it in my back pocket. i currently don't do much high strength so i'm ok from that aspect. thanks for the input. i love buying new toys for the lab hehehe (i feel like a kid again)

 

[cre781]

If they don’t meet the ASTM Standard we will correct the problem by sawing and then we break the specimens using unbonded caps (Neoprene) it seems to work fine for us..