View Full Version : GFRC (Glass Fiber Reinforced Concrete)

09/07/2017, 10:21 PM
Has anyone used this material before


It's basically concrete using chopped glass fiber as the filler.

While it still needs to be sealed, I think it has potential for large structural walls, beams and floors in a big tank?

Why concrete and not plywood? Concrete adheres to silicone... which adheres to glass. The idea is to make a composite tank with concrete for structure and glass for the viewing.

I've built plywood tanks, so I know how to use the silicone as a compression seal against a window frame. I also know that the window frame method can be done with glass inside concrete. But that's not what I want.

I want a clean smooth glass on glass edge and then a clean glass to concrete edge on the bottom (no lips) and back?

So - anyone done this?

Louis Z
09/07/2017, 11:18 PM
Oh . I have been wanting to do this for a long time . A friend of mine has this big heavy glass that was used in a bank . He doesn't want it and just asked me if I wanted it . I sai yes but it would probably sit in my garage forever because I didn't know how to attempt it . So I will follow along . My issue was sealing the glass to the walls . The glass fiber reinforced concrete was originally used by concrete slab manufacturers making table tops . What they used to use was rebar and the concrete had to be way thicker and heavier than what they wanted just to imbed into the concrete . So they used these fibers to produce a more flexible concrete that was stronger with the fibers . Thus allowing a thinner slab or tabletop. Now it really can't prevent big flex because concrete still has limitations of being easily cracked at stress points . The table tops are usually supported by plywood underneath so they don't handle very much eneven downward pressure . The pressure is spread out evenly so no cracking . Once this material is cast they usually take a flame to the surface to burn away any exposed fibers .

Louis Z
09/07/2017, 11:30 PM
I would think you would still need a thick portion of concrete to support the outward pressure of the water . As to how much I don't know . My original idea was to make the walls out of cinder block reinforced with rebar. I thought of pouring a slab with the rebar imbedded and then adding cinder block on the upright rebar . Then I would fill in with cement and vibrate it to get all the air out . I thought of fiberglass the inner surface but I didn't know if silicone would adhere to that . But if you say that silicone sticks well to concrete then that may be my answer . There is a local aquarium manufacturer that does the high end installations but I know I would never get an answer as to how they do it. But they do these huge built in tanks with a monstrous piece of acrylic that is really a showstopper .

09/07/2017, 11:35 PM
I'm going to make a scale model and test it first.

The first will be the in-tank floor/structural support... the next will be to replace the back and floor.

Here's the construction I'm considering (overall tank is 12' x 8'):

<a href="http://s1062.photobucket.com/user/karimwassef/media/Designs/1_zpsdljszdex.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/Designs/1_zpsdljszdex.jpg" border="0" alt=" photo 1_zpsdljszdex.jpg"/></a>

I'm still not certain of the adhesion strength. I'm willing to experiment though.


Louis Z
09/07/2017, 11:37 PM
Karimwassef . Since you live in Dallas you probably know the manufacturer I am talking about since they started in Houston and branched out to Dallas and Austin

Louis Z
09/07/2017, 11:42 PM
Is this in a room or building or outside? . I was only thinking of a front viewing panel where all the other sides were concrete. I wanted a lagoon where I could see from above and on the side of the lagoon .

09/07/2017, 11:53 PM
It's in a large greenhouse/sunroom

the build thread is all over the place:


09/07/2017, 11:55 PM
the local vendor uses PVC, as far as I know.

I was planning on plywood/epoxy for the bottom with a groove that the glass seats into. The back is glass with plywood backing for structural support.

09/09/2017, 11:49 AM
Anyone have experience with GFRC?

09/09/2017, 07:16 PM
Karim, you should look into undergrad "concrete canoe" projects. Lots of ideas, and likely a few papers covering the topic.

09/09/2017, 07:21 PM
wow! great advice. They're solving the same problem...

make it strong, make it light, make it waterproof!



09/14/2017, 07:04 AM
Looks like this should work, but I'll have to run some experiments first to get a handle on strength, shrinkage, etc...

Added a video that shows how I plan to use it to my main http://www.reefcentral.com/forums/showthread.php?t=2589632&page=25

Separately, there a material called concrete canvas that comes in rolls - some interesting potential http://www.concretecanvas.com/concrete-canvas/general/what-is-it/