# Experimenting w/ Lightweight Concrete Mixes + Fillers



## Tscarborough (Feb 25, 2006)

Dollar wise, more than you would spend buying white portland.


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## jgray152 (Oct 4, 2009)

ah forget it then.


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## Michael Olding (Aug 5, 2008)

concretemasonry makes a great point. Just because a manufacture has a brand name on his bag doesn't mean you are getting the 'exact same' material product he delivered to you in the last batch. 

All he has to do is make sure his product means the ASTM spec associated without whatever product he is offering. How he goes about that is HIS BUSINESS and he isn't likely to share that info with you.

It is a very good to understand where your raw materials are coming from. At larger pre-cast and GFRC manufacturing plants they test all materials entering their facilities. They will pull hygrometer readings on polymers, test cements in various ways and make sure the sands are graded properly. After all their ass are on the line when they deliver their products to their customers so they have to make sure the purity of the raw materials they receive make the grade.

If they have a very large run for a particular job or client they will contract with their supplier to provide identical materials for that particular time frame. If they supplier screws them and sends something different they will know it. These guys didn't get big by being naive.

It all can get very complicated! Hehe... but for us simple installers it's just a matter of batching properly for any given job which usually isn't to hard.

Just an FWI if you have a carving or color job where tolerances are critical, order all your material right before the job begins and do your mock up from that batch. Just make sure each of your individual raw materials come from the same run or batch to assure consistency or you could be asking for problems.

Great thread.


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## jgray152 (Oct 4, 2009)

Update. I started working on the project again and have been very successful at creating a good mix and coming up with a good process for making it stick to the wall.

I have been using a 4:3 mix (cementerlite). 3:2 Acrylic mix (water:Acryl60)

Mixing it pretty dry but not as dry as my trick mix which looks "crumbly". I apply some bonder/water mix with a brush to the cured scratch coat & wait 1-2 minutes for it to get absorbed, then with a trowel apply this mix thin over the scratch coat and wait about 5-10 minutes for it to set up a little so it can get a good hold on the wall. I than apply with my hands another thin coat of concrete and mesh it into the slightly setup mix (without this step, your mix will fall of the wall) to create a good bond and right after without waiting I start throwing on the rest of the mix building it out 1.5"-2" thick. Sounds like a lot but it goes very quickly as you do this all from the same bucket of concrete. 

I found that process works awesome for bonding. I have some pictures I will upload and I was able to build out about 4" thick patty on the wall without out sagging, sliding or falling off the wall using this procedure.:clap::clap: I want to claim victory here. There is still a little work I need to do to get it perfect but its works REALLY good right now.


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## jgray152 (Oct 4, 2009)




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## Michael Olding (Aug 5, 2008)

Looks like your gettin' that faux stone down jgray! Looking good.

By the way did you ever settle on a mix design?


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## jgray152 (Oct 4, 2009)

This Michael!

I haven't 100% settled on a mix design yet as I am still pushing some limits to see what will work and what wont. At this point, my mix is 4:3 cementerlite, 3:2 water:acryl60 and mix is pretty dry. More dry than you may have see before.Also trying to get the mix as light as possible. I think I have reached a close limit on my cement/perlite ratio because now if I try to move the mix on the wall with my hands, say I try to round a corner, the mix will separate or crack a little and it will have a hard time bonding together again. I have seen this on my exterior applications when I have to much sand in the mix, once I start bringing up the cement content, the issue goes away. At this point though the cracking is minimal and for the most part can be rubbed a little in that one spot to make it go away. So I think I will stick with the 4:3 mix or maybe go up to 4:3.5 (cementerlite)

Of course, if I ever add pozzolan, better acrylic polymer or water reducer I might be able to up the perlite content and either have it act the same on a minimal point or have it not crack/separate at all.

I have been designing faux stone exteriors for a while now but plastering on a vertical wall and having it act right and making it look good was a different story. Different technique, mix and animal altogether. http://www.stoneteknh.com. You will see what I do normally. 

I would have not made the stone so "round" but my initial mix I was using had fibers in it which caused all the edges to round over and crack apart when carving. So now I have to keep rounding the edges. Looks good and a little fake but I'll get there 

I wish I had some texture rollers and mats to work with. Then it would look REALLY good.:clap:


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## Michael Olding (Aug 5, 2008)

It looks like your mix may be up to 3"+ thick... is that correct?

I'm not sure how well the perlite will hold up in the freeze-thaw cycle myself but for interior use it's a no brainer. Though I add some vermiculite to my exterior mixes when I need to I'm pretty conscious of how much water may invade a wall system that I am working on.

Also for decorative overlays on the exterior your likely to have to rely upon an excellent acrylic sealer to deflect as much water as possible. I haven't tried a quality masonry sealer as I don't want to take a chance with excessive moisture buildup.

I overlayed my chimney a few years back and today after 2 solid days of rain I'm starting to notice some saturation. I may have to re-apply the sealer again this year to protect it. 

Overlays are exotic and can require some serious planning and thought but they sure can be beautiful can't they?


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## jgray152 (Oct 4, 2009)

The mix is about 1.5" - 2" thick on the wall. That large pancake I made is about 4" thick and I only wanted to see how well it would hold up (Sag or detach from the base). It did really well.

Honestly even an acrylic sealer still lets some moisture in. I have seen where I leave some water on an acrylic sealed concrete driveway and after some time it will soak into the surface. 

This is where you have to decide weather a breathable sealer, which can look best for faux stone, or an acrylic non breathable (supposedly non breathable) sealer would work best. I believe a breathable sealer would be just fine. As long as you have some sort of acrylic polymer in your mix to help reduce the amount of micro pores in the matrix and also reduce or eliminate efflorescence, I think a breathable sealer will work just fine.

I have used Behr Masonry Sealer (Natural) on my exterior concrete retaining walls and so far so good. After the snow is gone I will comment more on this after inspecting some of my walls.


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## jgray152 (Oct 4, 2009)

Bringing back an old thread just to give you a small update. Just remembered about this thread actually.

All the mixes seems to be holding up very well. No shrinkage cracks, only cracks there were are most likely from the wire mesh not being secured good enough as you can close the cracks some by pushing on them. Most of the wall was about 1.5-2" but looking at some areas I actually had it easily about 3" thick

I'm going to come up with another mix, though not sure how well it will hold up since the under coat will consist of a much heavier dose of perlite to make it very light weight, build out easy, sprayed on as a semi slurry coat with an accelerator in it so I can build on top of it quickly to get the desired thickness. After carving the faux stones, trees whatever, wait till the top coat cures out a bit, either waiting 24 hrs or 20-60 minutes, which ever is better, and spray on a top face coat to texture, shape and color. This won't be for awhile though.


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## Sir Mixalot (Jan 6, 2008)

Thanks for the update J.:thumbsup:
Any chance you could repost the photos again?


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