Consumer grade ballistic concrete testing

2 more days and back to your regularly scheduled distruction. I eagerly await the testing of my 1x and 2x poly mesh samples and the 50/50 poly strength booster and water mix sample.

Now I think I might want to make my own mix. Mix up some 1:1:3 and 1:1.5:2.5 ratios, using 1:0.3 cement to water ratio, then wet cured.
For example the standard 4,000psi mix is probably roughly 1:2:3 mix, using more like 1:0.5 cement to water.
I bought a sack of Portland cement last week, then today's at Lowes I picked up a damaged bag of general purpose sand, damaged bag of quikcrete gravel, and torn bag of large dranage gravel which is up to about 1 inch in size.
The damaged bags are $1 each.

 

My crack resistant concrete sample cracked when the form absorbed water and shifted.
Oh well. I'll make another one. With less water this time and a plastic liner on the bottom of the form. So if the wood does shift it doesn't pull apart the concrete.

Today I'm making a sample with 4,000psi concrete adding 6oz of Portland cement and 2lb of additional large chunky aggregate.
This should turn cheap small aggregate 4,000psi concrete into 5,000. For less than $20 per yard.

 

Alright I made the 5,000psi cracking resistant "pro finish 5000" sample this time with the correct amount of water.
I used about 1/3 less water for the same consistency as compared to the 4,000psi mix, the 5,000psi mix looks like it has a lot less sand and it has to have water reducer or super P already in it.

I made another sample with 4,000psi mix with 6oz more Portland cement and about 2lb more 1 inch aggregate. Took a little less water than standard 4000 mix, only like 10% less. I start with about 2.5lb less 4000psi mix and add it back with rock and cement.

 

New fumed silica test.
I found fumed silica, 10lb for under $100. That would allow some one to put 5lb per yard for under $50 a yard.
My previous fumed silica sample used a gram or 2 which volume wise was 1/4 cup. Now I can use almost a half ounce, by weight, volume wisee that should be a cup or 2 possibly.

 

Testing single plastic mesh layer reinforced no thrills 4,000psi concrete.
First shot doesn't do much like always.
Second shot cracked the sample all the way through in a few places, no spalling on the back.


Third shot, more cracks on the back side.

Forth shot, more damage and cracks.
I blurred the picture, didn't know it.

After the 5th shot the sample is all broken apart, but no hole.
It doesn't look as bad in the picture.


I put the 6th shot in the middle of the 5 shot grouping and it punched through. You can even see a little piece of plastic mesh sticking out.

 

Now the 50/50 polymer test.
First 2 shots landed closer together than I would have liked but oh well.


I put the third shot off to the side a little but it didn't help.


Poly booster helps a little but not much. I have had control samples fail after being shot and having 2 rounds this close together.
This is about $150 per yard worth of poly booster.
Spend the money on something else.

 

I made some house mix.
1 part portland cement, 1 part sand, 2 parts aggregate made with 25% small aggregate and 75% chunky aggregate.

 

My mix seems to be pretty rich in Portland cement. We will know in about a month.

 

I have been reading up on adding fumed silica to concrete.
It seems like you need alot. Something on the order of 5% by weight.
So per yard you will need around 50lb of fumed silica per yard for something like a 2% to 3% increase in strength.
So this one is not looking good either.
We're talking something around $200 to $300 per yard for maybe 3% increase in compressive strength.

 

Vibrating concrete, waste of time.
2 shots almost causes it to fail.


Third shot, done.

 

The 2 mesh test.

After 3 shots.


4 shots.


5 shots.


This is 5 shots, the back side.


6th shot broke through.


The mesh worked very well. The main problem is the plastic mesh on the strike face is shredded by high velocity ejected material. But the internal single mesh and double mesh on the back side did very well.

 

Finally found something that you can add to the concrete to make it stronger.
Nylon fibers.
Interesting result, when the round struck chunks of concrete that would normally be blasted away were held on by fibers.

Definitely need to test double, 3x and 4x fiber mixes. And go full scale.

 

I need to find something to increase air entrapment.
I'm thinking Styrofoam beads and something to just make the concrete hold more air on its own, since the air removed test samples failed spectacularly.

 

so are you thinking of using poly fiber instead of mesh or are you considering both? (btw I am really enjoying your experiments thanks for sharing the process and the pics)

 

Depending on the application, yes both.
The outer mesh keeps aggregate from being blasted away and when cast internal keeps cracks from forming.
The fiber keeps chunks of cement, small aggregate and sand together, also keeps these chunks from being blasted away.

As it turns out some of the cheaper things you can add to the concrete, such as plastic mesh and fiber appear to be most effective.

 

How about pearlite ?

 

I think Pearlite would just blend into the mix, unless it's special property is to make concrete more air entrapment friendly?

I got the Styrofoam beads ordered.
I'm thinking I will just use 2.4 grams of Styrofoam like I did with the 2.4 grams or fiber.
2.4 grams puts about 1lb per cubic yard.
No luck finding an actual air entrapment addtive, I know they are out there.

See my original wild as guess or hypothesis was that air entrapment was going to be bad.
Well testing shows the exact opposite of that.

So at this point my ideal balistic consumer concrete system is looking like standard 4,000psi or maybe even 5,000psi large aggregate mix with expanded metal on the out side, just below the surface, a matrix of plastic and/or metal mesh in the form, using low water and probably a water reducer or super plastisizer with lots of fiber added to the mix.
And maybe additional air entrapment.

I have super plasticizer, need to do a test with it.

Super plastisizer costs $20 per yard max. I'm thinking if you add $20 per yard worth of super plastisizer you will get concrete soop, which you may not need unless you are pumping the concrete.
So $10 per yard may be more than enough for a non pumping application.

 

Oh I didn't know that they made then into pellets. I have seen this used to fill voids in concrete block walls. I just didn't know what it was until now.

Let me test the Styrofoam beads then I can do this other material. Styrofoam beads are almost as cheap as dirt and we can get them any where.
The info I found on vermiculite had no mention of it's use in concrete.

I have considered using "volcanic material" like pumice or lava rocks but they are pretty expensive and ruled it out just on price alone.
Let's assume that there is a better source for it out there.
I will see if I can put together a test.

I figured the porous highly unusual surface of volcanic rock would make for a really good aggregate if it wasn't so expensive.

The cost of my ideal theoretical consumer ballistic concrete right now is between +$50 and +$100 per yard, in addition to the cost of the concrete.
This price depends on thickness, how cheaply you can get the materials.
Thicker concrete actually will lower the price per yard since you will have more concrete assuming using the same number of layers of meshes.
And depends on how much of a bulk discount you can get on fiber, meshes and super P.

I also believe energy efficiency should be a consideration too. Because if you spend less money on heating, cooling or cutting fire wood you have more time and money to do and spend on other stuff.
Plus the sales pitches on these concrete homes is the structure is essentially maintenance free, which again means you have more time and even more money for other "stuff".