Fiber Reinforced Concrete vs. others

[Kevin Cole]

Hi all:

I've been hanging out here quite a bit over the last few weeks, reading up on the discussions and trying to immerse myself in the concrete countertop segment of the industry. The information found here is very enlightening and I'm learing a lot (thanks to all of you). One thing I am curious about, though, is what types of concrete are most prevalent in countertops. It seems that GFRC is becoming more popular and has some real advantages, but it is really difficult to find any information on what percentage of concrete countertop manufacturers are working with fiber reinforced concrete vs. other types. I would love to hear your opinions on what percentage of tops being done are fiber reinforced -- 25%? More? Less?

Thanks,

Kevin
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[Mark Celebuski]

I believe we have a skewed sample on this forum.

I would guess that about 90% of concrete countertops are currently wet cast.

Fibreless, steel rebar using, wetcaster. Does that make me a socialist?

Mark C

[Philip Ferreira]

Alla

With regards to the defoamer, you say you use the real stuff, is that the diluted TBP or the defoamer from BASF? If you are using TBP, at what concentration? And where do you get it? I'm still trying to find a local BASF rep, my Grace guy was laid off and the new rep is useless, hence, they have been no help.

Thanks,
Philip Ferreira

[Alla Linetsky]

Philip, I use full strength tri-butyl phosphate. The product I have now I actually got from BASF as a freebie - helps to be friends with the guys in the lab. But before that, I used to buy it from Fisher Scientific. Look them up, call their customer service no. and they will put you in touch with your local rep. Most of those guys work out of their basements, and they will deal with anyone. A 500 ml bottle would last me over a year, and cost about $50.

For any defoamer to be effective, you must have a very fluid self-consolidating mix.

And Mark, you're not a socialist, you're a Luddite. Time to leave the stone age (pun intended). Although I have to agree, with the span like in your photo, I'd put some steel in the front edge too.

Philip Ferreira said:

Alla
With regards to the defoamer, you say you use the real stuff, is that the diluted TBP or the defoamer from BASF? If you are using TBP, at what concentration? And where do you get it? I'm still trying to find a local BASF rep, my Grace guy was laid off and the new rep is useless, hence, they have been no help.
Thanks,
Philip Ferreira

[Philip Ferreira]

Thanks for that Alla, I'll see what I come up with.

[Mark Celebuski]

Well thanks for not insulting me, I think: http://en.wikipedia.org/wiki/Luddite I have not destroyed a loom since the 80's.

The truth is I’m willing to try anything. I used to sub out exterior building wall panels to a company that would make 48’ x 10’ GFRC wall panels. Having seen them cast and erected I know just about anything is possible. That said I’ve wet cast many similar sized structural panels that performed functions GFRC was not capable of.

I use the method, or combination of methods, that make the most sense for the look I’m after and the ease of casting.

The lines between GFRC and wet cast are very close to merging when it comes to concrete countertops. If I wet cast a slab with no steel and glass fiber as the primary reinforcement is it GFRC?

Mark C

[Mike Cook]

Great question Mark. My answer would be no.
If you are using an absolute minimum of 4% + glass content then it is classified as GFRC. The majority of us do not do this. (it is not nessesary) Besides it would be very difficult to work with a loading of 4-6%. Those type of %'s are traditionaly accomplished with a concentric chopping gun as I am sure was used to make the panels you described. The industry uses the term Premix GFRC when refering to GFRC with less than 4% content. All of this is outlined in more detail in PCI manual 128 and 130.

I will also say this to all manufaturers doing premix GFRC. " Be careful when telling an architect or engineer that you do GFRC. GFRC to them is defined under UBC, IBC, NBC, and ICBO's. They may assume that you are producing a true GFRC @ 4-6% and it could land you in hot water."

[Alla Linetsky]

Mike, could you please explain what those acronyms stand for? Also, how could a lower % of fibres land us in hot water if the concrete can still handle the stresses it is exposed to? Would anyone actually take a piece of solid concrete and measure the fibre content?

[Mike Cook]

International, Uniform, and National building codes.