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Lightweight Concrete

13 years ago

I know there have been dozens of discussions about this, but I can't seem to find my specific questions answered when I search the forums or the Internet. Wondering if someone here can help!

I'm trying to lighten my concrete yet still keep the strength. I'm making concrete stools, end tables and yard ornaments. The surfaces will all be either stained or covered with mosaic, thus I am not out for the finish one gets with hypertufa, nor will I be doing any carving.

Really, I just want to make something that's as sturdy as the concrete I've been working with, but a little lighter.

What's confusing to me is whether or not I need to add something to strengthen the mix if I start adding perlite. I've found a recipe that calls for 1 part Concrete, 1 part Sand, 2 parts Perlite, but in the same conversations people casually toss out comments about "admix", "latex", and "plastic fibers". I'm not clear on whether that's required, and if so, what are they exactly and where would I get them? I've also read that the perlite I'm looking for isn't the perlite I can buy in the potted plant section at Lowes. Is that right? Could I avoid additives if I went with 1 part Cement, 2 parts sand and one part perlite? Even a little lighter would be nice if it doesn't compromise the structure.

Like I said, I love what I've been making from the standard mortar mix, but I'd just like it a little lighter. Seems like an easy thing to look up on the internet, but I either suck at searching or there's no straight answer!

Thanks in advance for any advice you can offer!

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Comments (4)

billie_ann
13 years ago
Are you making these solid or are you putting your mix on an armature?
We don't usually use concrete which comes already mixed in a bag and the main ingredients are portland cement, sand and gravel.
You can use your mortar mix on an armature then mosaic. Billie
loribee2
Original Author
13 years ago
No, this is solid concrete. Since they're stools, I want them strong enough to sit or stand on. I'm using a 5 gallon bucket to cast the base for the stool. I plan to cast it with a 4" PVC pipe in the center so it will have a hollow core. But I wanted to also try lightening the concrete as well using perlite. Just not sure if I need to put any other additives in it to recover the strength if the perlite weakens it.
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tishwish
13 years ago
loribee, I think you need GFRC- Glass Fiber Reinforced Concrete. The fibers can be bought at a mason and concrete store.A little bit goes a long way and is cheap.Wear a mask and mix well. No perlite needed because the object can be made thiner and or hollow. Google GFRC and Youtube it to study up. You can even bend the concrete and have it stay in place after it dries. Have fun and good luck.
loribee2
Original Author
13 years ago
Wow, that's a technique I haven't heard of. I will check it out. Thanks!

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