No Polymer GFRC

[Eciton]

what would be the downside to doing small projects (bench tops, small tables, etc) sans polymer?

is it just a requirement of a wet-cure and prolonged demould time or are there more reasons?

does everyone put fibers and polymer into sample pieces?

just wondering.

[Gregg]

I always use polymer in whatever I do because it effects absorption and stain resistance. Even in samples because it can have an effect on color saturation.

I don't use fibers in samples though.

[Alla Linetsky]

I've made polymer-free gfrc with qwix. The polymer helps, but the table top I made (in my office/showroom) is plenty strong without it. Liquidz increases strength by about 30%, other polymers not so much. I just like the way the wet mix behaves with the polymer, but it's not the end of the world if you don't have it. You need to cure your concrete a lot better without it.

[Dave Solursh]

Hiya, Alla, when you say you use No polymer, do you mean like no Forton (etc...) Or are you including Z in the umbrella of "polymers" I use Z in everything I do, Wet cast or GFRC, am I spending $ I don't need to adding "poly" on top of Z when doing GFRC? If I skip poly in GFRC (but Not Z, never would skip that Unless other poly give me better results, just haven't gone there yet) should I just cure longer.

That table you made when I visited last, used only z for a GFRC no steel mix and I was curious about that and never asked if Z was doing what all the other Polys are doing.

[Alla Linetsky]

Dave, I use LZ as my polymer, nothing else. For a little while, when we ran out of it, we made a few pieces without it. The first was a table for our shop, and it turned out OK. Still, I really like what LZ does for my concrete, so I'm using it in all my pieces.

[Dave Solursh]

So are you able to pop out in 24 hrs then with LZ and Kwix for your GFRC mix and NO metal! No more Wet cure after that?? Way cool, if so I will give it a whirl on a test piece.

Have to come for a visit soon.

[David Manchester]

Anyone Use Z and Forton or Polyplex? I just finished a double bowl 6' x 1.5" vanity

piece with Z , Supersealz and VCAS, along with Super flowz with 3 oz per cu ft of Fiber. I used standard Portland and a mix of mason's and white sand. I also used threaded rod across the piece as reinforcement. While moving down some steps the hand truck fell the 8" drop from the last step and the piece cracked. I knew I should have made a crate for it but I was not traveling that far and it was a test piece anyway. I was surprised that it cracked since it had seemed so much stronger than my normal mix. Would Forton or Poly have helped? I am casting it again and forming two integral "beams" to travel underneath and tie the two sinks together.

[jschuler]

where did it crack? and what type of crack.....could you take a picture, how much curing did you do, and how old was the piece when you moved it?

The next question, if you are going to recast....here are a few things that I have learned make a HUGE difference in early strength.

What Portland cement are you using?
What was your w/c target?
What was your Z loading?
Add some Nyad G in as part of your sands.
Increase your fibers. 3oz per cuft, just isn't really enough in my experience and testing. 5-6 oz would be my lowest recommendation...based on beam break testing.

Post your mix....and lets see if there is room for improvement. Or e-mail it to me [e-mail],

That is a nice looking vanity, what is the block design on the center?

[David Manchester]

John,
Thanks for your reply. I used Lafarge portland (grey). I followed your suggestions as well as Blue concrete's for the use of each of their products. The only thing I think I did undershoot was the fibers in fear of having too much exposure. That is why I ran the 3/8 threaded rods(front and back) through the center of the piece. The vanity cured for three weeks before the move. I shot for a .33 w/c as you suggested , replacing 23% of the water with Z. What is Nyad G? Where can I get it? The vanity cracked along the right side of the left sink and the left side of the right sink, small hairline cracks that ran from back to front of the piece. I can take a picture and post it later today after work. I think the integral beams running from each sink underneath will definitely help. I was just surprised that it did crack since I have been reading about some of the results people have been getting with this mix. I still have the backsplash piece( 6'x1") that I will test (after I successfully repour and install the next one) that I will keep and try some tensile strength testing on. Here's a photo:

The block design in the center is for a flower vase or toothbrush tray..something to place things on. The depression will be to set matching slate that is used in the rest of the bathroom.

[jschuler]

That all sounds just fine. Here would be a few suggestions, based on the way we work with the same type of double integral vanity sinks.

I shoot for a bit lower w/c. Not much, .31 is my high end.....since you are dealing with two small beams, (front and back of the sinks), holding everything together. And, the back beam has holes in it...for faucets.

I push my fibers a bit higher for these 7 oz a cuft. Then I lay 2 layers of scrim top and bottom, like a sandwich, to hold both potential cantilevers....while dealing with processing and install. Once installed, it really doesn't matter....unless the cabinets move.

The Nyad G, this is a mineral based fiber, that is added to your mix as part of your super fines, I have found the optimal is about 10 percent of my sands. With the testing we have done, we have found these fibers, added as a percent of your sands pushed flexural strength up 20+ percent....compared to similar mixes without the Nyad. They also have increased surface hardness significantly. So now, it is in everything we do.

BlueConcrete distributes these fibers. Give Julie a call and get some. I recently posted a picture of a double integral vanity sink top that we finished, with similar design.

Also, if you are not using Qwix.....get some. Qwix has some amazing properties to increase strength. We have seen pretty big improvements by using as littel as 5-6 percent additions. IMO, the Qwix really helps to save a mix that needed higher w/c. Since the Qwix, uses much more water than conventional Portland cement mixes....it sort of dehydrates quite a bit of the water from the mix....by forming it's strength characteristics.

[jschuler]

I forgot to add, for these projects we use what I call...."vibratable hand pack mix"....it is a stiffer mix, but the faces vib out amazing, and I don't need a hat mold for the sinks. With more fluid mixes you need a hat mold....I hate those. So I do everything I can to avoid them and still get clean faces.

Looking at your pic, it looks as though you have a saw horse supporting both ends and one at the spot where you had a crack. Is it possible that while storing this top, your supports may have contributed to the problem? Drop a straight edge on the top, next time you support something that way.....see if the center saw horse isn't pushing up. If we do that, I just put a few 2 byes across from saw horse to saw horse....none in the middle of the top.

[Ryan Waxman]

i have about 3000 pounds of NYAD G i am looking to sell, 50 pound sacks.


jschuler said:

where did it crack? and what type of crack.....could you take a picture, how much curing did you do, and how old was the piece when you moved it?
The next question, if you are going to recast....here are a few things that I have learned make a HUGE difference in early strength.
What Portland cement are you using?
What was your w/c target?
What was your Z loading?
Add some Nyad G in as part of your sands.
Increase your fibers. 3oz per cuft, just isn't really enough in my experience and testing. 5-6 oz would be my lowest recommendation...based on beam break testing.

Post your mix....and lets see if there is room for improvement. Or e-mail it to me [e-mail],

That is a nice looking vanity, what is the block design on the center?

[John Cardwell(www.crete-unique.com)]

I agree with Jon we rarely support pieces in the middle like that. If the floor isn't level one side or the other can take some undo stress. Also if you had that on a hand truck and weren't carrying it on edge that would be a big reason why this happened. No way much wet cast especially with two sinks would handle a drop like that if it were on a hand truck with the flat side in I imagine. Installing is sometimes way more than half the battle.