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Old 05-18-17, 08:17 PM   #1
oil pan 4
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Default Ballistic concrete

All these tornados and such got me thinking.
With modern materials why are homes getting flattened by twisters?
So I thought the obvious solution is concrete.
Not just any concrete, ballistic concrete. It's got to be strong, crack resistant, if it does crack some that can't be the cause of failure and it has to resist penetration.
I could call it tornado concrete but that name sucks.

I also want to latterly develope better stucco.
You might think stucco looks tough but I got an over grown bb gun that can blow a hole through standard stucco. I have already developed stucco that can stop a 9mm round, an unexpected result I should add.

The scope is to take existing easy to get materials, combined them, improve them, test them for improved strength and toughness. See if the added cost of better materials is cheaper than just casting thicker concrete or just to improve strength if you are limited in thickness for some reason.
For example polymer concrete strength booster it's like adding glue that helps the concrete stick together better, it's expensive at $15 to $17 per gallon. I think wetting cubic yards with this stuff is unrealistic and not in very many people's budget, but maybe using 10% to 50% is, but is it worth the added cost?

Standard concrete has no steel or fiber reenforcement, it's compressive strength is around 4,000psi.
"Military grade ballistic concrete" is 5,000psi and has up to 30 pounds of steel per cubic yard.
High strength concrete can be up to 6,500psi.

The Internet doesn't say a whole lot about ballistic concrete. You're pretty much limited to "make a wall like this". I want to be fully scalable from improving stucco to building a fortress if that's your thing down to making a concrete counter top that won't crack.

My testing will be with 11.7 inch squares that are 1.75 inches thick. That odd size just happens to be the same size as a "1 foot square paver block".
I figure that sample size will be cheap to produce, be easy to move, easy to reproduce.
The standard size hardware store paver is going to be my instant cheap control test.
Test blocks have been cast and have been set aside to cure.
Paver blocks have been destroyed with various weaponry.
Masonry will be harmed in the making of these posts.


Last edited by oil pan 4; 05-20-17 at 08:21 AM.. Reason: Added the "For example"
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Old 05-18-17, 10:12 PM   #2
oil pan 4
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Concrete forms.


12.7 square samples, 1.75 inches thick, made so far:
A control made from low slump 4,000psi common concrete.
Low slump sample made using 25% acrylic polymer booster, common 4,000psi concrete.
3 samples made from the same mixing of standard 4,000psi concrete, medium workability.
One sample is a control.
The second sample had stucco supporting mesh cast into the center. As if the mesh were suspended and cast in the middle of the wall.
The third sample I tossed a 12 inch square mesh in the bottom of the form sloped concrete on top of it then set another 12 inch square of mesh on top and pressed it lightly into the concrete, as if a wall were made with stucco mesh lining the form.

In a few days when the day old samples are nice and solid I will drop them out of the forms and make some more. The goal is to start making 1 or 2 sets of test samples per week until lots of different test combinations are sampled.
I have 5,500psi and 6,500psi mixes and polymer booster, steel a concrete vibrator and a vacuum chamber.
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Old 05-19-17, 01:12 PM   #3
oil pan 4
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I was thinking about the addition of steel to concrete.
So I decided to weigh my stucco mesh to see what adding it to a wall would total out to be.
One yard of concrete poured into a 4 inch form gives you a total of 81 square feet of wall.
1 square foot of stucco mesh gives you 3.1 ounces of steel.
So one layer or stucco mesh spread over 81 square feet is almost 16 pounds.
If 2 layers of mesh are added to the wall forms and the concrete poured in that gives you 31 to 32 pounds of steel per yard.
Military grade is 30lb per yard.
So that should be quite sufficient.
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Old 05-20-17, 05:22 AM   #4
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Not to be a Debbie Downer but I'm confused by what you are trying to do.

The impact resistance of concrete is well understood, and cost effective measures are already available. The issue is cost effective is still very expensive. While the compressive strength of concrete is an important part of the design, the real weak point is the tensile strength. Stucco Mesh is way to small to impart enough strength to the concrete to impact survivability of a structure, unless enough is added to equal the weight of steel you would otherwise have added. At that amount though you have issues with even aggregate spread within the concrete, and it would end up being more expensive than traditional systems (by weight stucco mesh is more expensive than re-bar as it is more refined and processed).

For stucco applications a 12" square is not the right testing dimension, you should start out with 16", and then work up to a test wall.

Also the materials aren't as important as the assembly. The weakest point is generally windows and doors, not walls. After that it is roof and foundation attachment, then wall and roof strength. At least as far as structure survive-ability is concerned. Even with great roof and wall survive-ability the weak points of windows and doors still lead to a need for hardened storm shelters inside the house.
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Old 05-20-17, 08:10 AM   #5
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The impact resistance of concrete is well understood by whom exactly?
Because who ever they are it doesn't appear that they have published much of what they know to the public domain.

I have 2 issues with stucco mesh being too small to help.
1 has anyone actually ever tested that idea?
2 rebar can't be everywhere unless you are going to use hundreds of pounds per yard, this is only 16 pounds per yard in a 4 inch wall and it's everywhere.

It may only be cost effective to use the mesh in small amounts, say to add it around windows and doors or where you have a window next to a door where a real narrow section of wall is created or to use it to build an above ground storm shelter.
I believe that the same thing was said about applying rino liner to masonry buildings to make them more blast resistant; that it's not rebar, it's just thin plastic and won't help.

My stucco tests aren't even 12x12 I am just establishing a base line using scrap pieces cut off my house when I installed larger modern windows.
From my tests I already know larger samples would be better.
It doesn't get any more realistic than testing actual 50 year old stucco.

These are just small scale tests. Where a small control sample will be compared to something else of slightly different composition of the same size.
Large scale tests with larger samples will be later.

Isnt it obvious that roof attachment and foundation attachment are way out side the scope of this why even bring it up? This is only materials testing for the purpose of selection and cost compairson.
Basically I'm comparing OSB to plywood, your talking about how to design a house... Why?
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Old 05-20-17, 10:12 AM   #6
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What about trying masonry/timber structures? I'm not sure how well it would stand up to a tornado, but interleaving wood with masonry apparently results in structures with excellent compressive and tensile strength at relatively low cost.

http://www.iitk.ac.in/nicee/wcee/article/13_2297.pdf
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Old 05-20-17, 10:19 AM   #7
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Go to a library, and look it up. O.K. you might need to go to a library at a school with an architectural or structural engineering program. Failing that Google Scholar list over 3,000,000 articles in a search for "concrete impact resistance". Most of the newer ones deal with fiber reinforcement.

As for your issues:
1. yes people have tested the idea, the result is that you need a relatively even mixture of your aggregate throughout the concrete. In a wet pour a hole sizing that is close to the size of the aggregate does not allow the aggregate to free flow, causing it to collect near the mesh. It works in stucco because it is used as a lath, something for the concrete to grip onto. If it were layered into wet concrete it would probably work well, but then you are vastly upping your labor requirements.

2. I completely agree, but you have to keep the aggregate size in mind too. it has to work as a system.

As for Rhino lining for blast protection, I don't know who would have said that as the same basic principle has been used since 1936 in car windshields and windows.

Sorry but roof and foundations not being in the scope isn't completely obvious. Sure you want to increase the strength of concrete, but why? For tornado resistance? If so what are the goals? To reduce rebuilding? or protect the occupants? That is what defines your scope not material properties.
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Old 05-21-17, 09:57 AM   #8
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I looked at 200 to 300 of those links.
They had some general useful information, such as the vacuum concrete. Not my idea at all.
And that surface treatment chemicals are pretty much useless.
A lot of it was to do with sky scraper or bridge super strong concrete that none of us will ever be able to get ahold of. If you were to start calling around asking get for some samples I'm sure you would get a visit from department of homeland security.
Also there were a lot of links trying to sell something, of course careful not giving up any useful information.
Lots of lab studies.
Some guys with rifles shooting concrete samples. No indication on what type of concrete they used, how it was mixed or how long it was cured.
Concrete wear testing.
Both general info and lab tests on concrete repair.
More lab studies.
Sea water's effects on concrete.

For concrete testing what I'm doing with the samples is taking normal concrete, changing 1 or 2 variables and testing it against a control.
For stucco I'm going to take existing stucco and see if anything can be done to make it any better, originally I thought was going to be pointless but I have gotten good results so far.
Then last I may test out a few surface treatments to see if say existing concrete can be improved.

Possible applications are everything you mentioned and more geared toward the DIY'er. Compared to 98% everything I found was at least commercial to public works scale.

Last edited by oil pan 4; 05-21-17 at 11:20 AM..
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Old 05-22-17, 10:53 AM   #9
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I for one support your idea of shooting 12x12 squares of concrete, if not for any other reason than it sounds fun. If you happen to come across some sort of extra-cost effective and novel method of reinforcing concrete more power to you. I personally have been interested in coming up with some bullet resistant structures that fit in around the house decor (bookshelves and such), and have some ideas that I of course am going to have to test via ridiculous amounts of shooting at things. Sure I could google some of it, but then I wouldn't get to shoot stuff.
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Old 05-22-17, 11:30 AM   #10
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Yeah since I can't build full scale walls, and blast them with 2x4 studs from my air cannon or some other debris my regular cannon. 1'x1' squares 1.75'' thick and a 22mag will have to do.
A 50lb bag will make 2 of my samples with a little left over.
I have exactly one bag of 6,500 psi concrete so I hope that I can get 4 samples out of it, because the next nearest store that has it is 85 miles away.
22mag does a number on the store bought paver stones which are mostly sand and air. If the concrete samples turn out so hard 22 mag isn't doing much then I can step it up to 30 carbine. But I know 30 carbine will blast pavers to rubble with one shot, I'm assuming the pavers are almost as strong as concrete.
Yeah it's pretty easy to look up how thick of concrete to stop a certain round.

I checked on my high vacuum concrete today. The exposed sample does not look like regular concrete. It almost looks like grout. It's very smooth very few bubbles and all I did was slop it in the form just as I did with all the other samples.

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