Lightweight Concrete

I have seen a show from the UK showing mixing concrete with styraphoam plastic, that mix was quite light and when used with Iron braces it was quite strong.

Might that be what you are seeking?

My father and i tried manufacturing and marketing modular houses made from the same kind of mix. Used Portland cement your standard aggregate and some Styrofoam bead however a plasticizer was necessary to keep it from cracking even with the rebar. Thinking back short fibrous Kevlar strands in the mix might have been better. Like they use in castable refractory.

People were reluctant to let go of there wood houses.

Yes I had a feeling that there was a catch somewhere. I have seen the show and I thought I saw Gypsum or like mixed in the mix??

Hold on - the mental replay shows straw in the mix. So it must have come out like a Pueblo or a mud brick.

Marvelous stuff that old technology you know?

How much weight per unit volume you're looking at?

hello willyap06,

while researching lightweight aggregates i found a curve showing the different classes of lightweight concrete. the place on the curve am trying to reach is 15 pounds per cubic foot. or better, if i can do it.

to everyone else so far: thank you, but i have no interest in looking at or using any of the lightweight aggregates out there. reason: they all wind up with heavier denisties than i am shooting for. plus, they all have problems. ie: floating, sinking, compressing, or just not being light enough. i am only interested in air voids in concrete. but i do thank you for trying to be helpful.

Let's say normal concrete weighs 145 lbs/cu. ft. If you consider producing a "seemingly" lightweight concrete using the same kind of aggregates for normal concrete, at 15 lbs/cu.ft unit wt (of concrete+hollow space volume). you will need around 0.10345 cu. ft volume from normal concrete mix and will require a hollow space volume of 0.89655 cu.ft. per cu. ft. of concrete required.

Entraining air in this case is not going to work. The amount of entrained air is usually between 5 percent and 8 percent of the volume of the concrete, but may be varied as required by special conditions, but not so much.

Now, if your application will require insulation with concrete being your finished surface, you may consider some other innovative construction technologies, i.e., 3-D panel construction that use Modified Expanded or Extruded Polystyrene Core and 2" x 2" welded wire mesh.

Again, that depends on your application and/or requirements.

Small air voids totaling the volume of a few large voids would provide better insulating qualities.

Air-Entraining Admixtures

thank you stirling stan,

i really liked the link you provided. the info. found their was excellent. the only problem i am finding with it and most peoples comments is that it is the proper answers for air entraining into structural concrete to make the mix easier and to protect from freeze thaw.

now, i do have that application also, but that is in the outer weather surface layer.

the middle layer requires absolutly no strenth as it is sandwiched between strong layers. i am putting so much air into it that it is more like styrofoam than concrete. think "autoclaved aerated concrete". so, with that in mind, are all of the recomendations i find here for small bubbles being better, still valid?

Small AIR VOIDS and many /volume are always better than Large Air Pockets.

Old Soviet Building Construction Literature list properties of foam Concret,Gas concrete,concretes with blown Blast-furnace slag as aggregate etc.etc.

If your area has no natural foamy stony aggregates like Pumice,Perlite,Vermiculite---you can still create the foams in the setting precast shapes using Aluminum powder.

Maybe somebody tried petroleum (Butane/Pentane) expanders.

Ground-up Foamed polystyrene are used -I have seen in literature.

Bamboo fibres are used-Bamboo creates the tiny voids+reinforces too.

I agree ... smaller voids more volume will give it more strength then large voids. We experimented with adding small metal wires and passing it thru a magnetic field to align the wires. Idea was to give it structure to make up for the loss of compression strength. Didn't know enough bout Magnetics to balance the field right though. Kept pulling the wires to one side or the other. As far a gypsum never tried it, Did try pumice. Concrete got crumbly some maybe some kind of reaction with the port-land or maybe it just leached off the water to fast around the stone.

Why limit yourself to air? Any gas can be foamed or bubbled to produce your desired density. Helium would seem a natural if buoyancy is an issue. There is no reason your bubbles need to be created at atmospheric pressure, either. How about vaccuum bubbles? And yes, smaller voids are better.

We aerated portland based concrete all the time. There are limitations to what can be acheived with Portland as the binder

With Ceramic Cement as the binder we have viable insulation as low as 3 pounds per cubic foot. The "R" value of this is around 4 per inch.

Jonathan

Ceramic Cement Research Institute

479-899-7053

I'm not sure if you looked up foam concrete yet, but here is a link of one with some technical info provided. Most are using chemicals to create the aeration in the cement, but it will give you an idea of bubble size (10 to 50 microns):

http://www.alliedfoamtech.com/Appconc.htm

look at this! Could you place a polystyrene form in the mould to create the space, leaving you with this kind of effect?

Concrete is a mixture of cement, sand, and gravel. The weight of the material is primarily in the sand and gravel.

There are products that contain no aggregate, i.e. cement only, with air bubbles. One company that produces this is Cematrix.

http://www.cematrix.com/

They can customize porosity and density as required.

check out http://www.stalite.com/ They are experts

Hello ArtbyJoe, I was hoping for an update about your geodesic lightweight block project design.

I would like to build molds for cellular ceramic blocks for geodesic home structures

I mentored with Paul 'Gray and John August of Gecko Stone, and learned how to manufacture the Stable Air cellular concrete technologies equipment and mix designs. which I have evolved to cellular ceramics by utilizing ceramic cement composites.