Consumer grade ballistic concrete testing

space saved for later

 

Adding 1lb of chopped nylon per yard (the recommended amount) helped a lot.
Cost per yard, not much. I think I got my 1lb bag of chopped nylon for around $10, should be cheaper if you buy in bulk.
It made a very interesting crater. You can see how the nylon held on to material that is normally ejected away.


2nd shot was uneventful.
So on to 3. The sample was showing some over all damage but not as much as the controls.


Then a shot a 4th round pretty much into an existing crater, oops. But it didn't fail. No control sample survived anything like that.


And one more time.

 

When trying to decide which fiber, nylon or fiber glass would be best with out doing lots of tests this is what I found.
Left and center is chopped nylon. Its fine as frogs hair. Then chopped fiberglass on the right. The fiber glass is almost like stiff little match sticks.

Which fiber is better I think is like a question of sand versus gravel which is better.
Use both.
I believe the nylon fuzz will bind the material and just be kind of everywhere but not very substantial . Then the denser stiffer fiber glass will be more like tiny rebar, with far fewer but much stronger stiffer strands.

Close up of the fiberglass. The fiberglass does not turn to fuzz like the nylon, it stays as you see it.


Close up of the chopped nylon, its just fuzz. But damn does this fuzz make a difference.

 

Today I was able to cast 2 samples.
Using 1lb per yard of nylon and 1lb per yard of fiberglass, making this sample double the recommended amount of fiber.

Then I mixed up the standard medium workability sample using the standard Qt of water, added 3ml of super plastasizer.
This was so I could increase workability of the concerete with out additional water, then mixed in the Styrofoam beads and use my mixer and not destroy the Styrofoam beads.
I went with 1lb per cubic yard, or 2.4gm per sample just like I do with the fibers.
Then I ran out of time, had to go to work.
1lb of Styrofoam beads should be about 5.5 gallons of volume per yard lol.
I'm thinking each 1lb or 5.5 gallons of Styrofoam beads increases air entrapment by up to 1%.

 

5,000psi study.
Starting a few weeks ago I made 5,000psi profinish crack resistant samples. This concrete has fibers in it and appears to have water reducer already in it. These are basically going to be their own set of mini tests.
My house mix, the 7 sack 1:1:2 should be at least 5,000psi@28days.
Today I also bought the profinish 5,000psi with out fiber.
The fiber free 5,000psi profinish will be my control and I will see how my 1:1:2 house mix compares.

I also want to try going in the opposite direction. I would like to take some 4,000psi mix, cut it with more sand and gravel and turn it into more common 3,000psi 5 sack mix.
If there is hardly any difference between 5, 6 and 7 sack mix this would be great.
But the military has historically insisted on 7 sack mix, so that's kind of where I expect my tests to lead.

 

So far you have estimated the strength, and there's little doubt that the estimates are within the ball park. Other than cutting or casting coupons and glomming onto an instron machine that is destructive, there is a non-destructive testing widget The Schmidt Hammer has been in use for many years and has been quite precisely coordinated with destructive tests. Not a cheap toy, but will give seriously accurate results. It's been few years, but we used it as a quality control check of placed and cured concrete.
Schmidt hammer - Wikipedia
https://www.proceq.com/compare/schm...MIjYaSnMGW1QIVl4SzCh0FRQySEAAYASAAEgJ3-_D_BwE

There are some far less expensive Schmidt testers available, but I know nothing about the accuracy or calibration requirements.
Amazon.com: schmidt hammer

 

I could get one of those.
It might work quite nicely with my 320ft/lb tester I have been using.

Alright so today I casted another 4,000psi 2x fiber sample. The one I poured the other day got a big cracking in the middle, my test form got rain water on the bottom of it, the wood swelled and shifted then cracked the soft concrete.

I poured a non-fiber 5,000psi control sample.

Then took 4,000psi mix added additional sand, general purpose gravel and large chunky gravel to mimic a roughly 3,000psi mix I have seen people use. I'm assuming the 4,000psi mix is roughly 1:2:3 mix I boosted it to about a 1:3:4 mix.
I mixed up 20lb (normally I mix up 20.4lb) because i know it was going to be less dense and still had a good bit left over. So the 3,000psi mix is probably about 10% to 20% lower density. Probably around 15% cheaper to go with 3,000psi due to using 1 sack of cement less per yard.

All samples were no flow, low workability for simple straight vertical wall forms.

This way I will have tested 3,000psi, 4,000psi and 5,000psi cement, sand, gravel and water only control samples.
I have about 60lb of fiber free 5,000psi mix left so I will probably just pour 1 or 2 more control samples with it.

Because the price difference between 3,000psi, 4,000psi and 5,000psi is 1 or 2 bags of cement per yard or $12 to as much as $100 per sack of cement if you are way out there.
Then I should be able to draw some kind of conclusion between using 5, 6 or 7 bags of cement per yard.

So then I can take the best reinforcement fiber, the best mesh setup and combine it with the best concrete and have a resulting product that is far superior to standard concrete by it's self.

 

Found some breakdowns of which fiber does what.

There are 2 main groups of fibers, primary and secondary reinforcement. The primary reinforcement makes the concrete stronger, enough so it may replace steel.
Secondly reinforcement helps keeping the concrete from cracking during curing.
Some fibers do both.
For a secondary reinforcement uses 4 to 20lb per yard.

Nylon is supposed to only help during curing and provide no other benefit.
Too bad I tested it and found that it does.

The match stick fiberglass is a primarily reinforcement and should make your concrete stronger. If used in high levels such as up to 120lb/yd concrete engineered fiberglass can replace steel reinforcement in some applications. This must be why the concrete precast industry likes fiberglass.

Chopped carbon fiber does both primary and secondary reinforcement and gets compared to using steel fibers.

PVA fibers also do both. Supposedly stronger than nylon.

I'm testing 1lb per yard and got a very dramatic improvement.
Soooo it looks like I will be testing much higher fiber content samples, probably 1, 2, 4, 8, maybe 20 pounds per yard.

 

Using fly ash.
FLY ASH CONCRETE - WHAT ARE THE REASONS FOR ADDING FLY ASH TO CONCRETE?

Fly ash sounds like a cheap fumed silica cheap substitute. The fly ash or fumed silica soaks up the free lime and turns it into calcium silicate hydrate and calcium alumina hydrate. Which makes stronger concrete.

Using Fly Ash in Concrete

On structural concrete and precast. They're saying replace 15% to 35% of the Portland cement with fly ash by weight.

Using fly ash is supposed to make concrete less water permiable. A helpful tip if you live some where that sees a lot of rain or if you are building a water cistern or pool.

On the subject of fumed silica I did test test my sample.
It appears that the fumed silica did at least as well as a control sample.
I took pictures but the damage looked identical to control samples.

 

I bought some fly ash and chopped carbon fiber. Still lots of testing to do.
The carbon fiber is only 1/4 inch.

I wasn't going to bother testing pozzolanic material until the fumed silica test seemed to do at least as well as the control tests.
My WAG is that the high surface area of the fumed silica reacted with the calcium hydroxide producing more calcium silicate hydrate sooner.
Also I accidentally shot the fumed silica test a week early and it did as well as a 28+ day control.

 

My 4,000 psi concrete upgraded to 5,000 psi concrete by adding addition concrete.
Look at how much smaller the impact craters are.






It almost looks like it was shot with a 22LR.
This harder mix looks super strong. The rounds just appear to be bouncing off knocking loose a chip of concrete.
And it broke.


What happened? It seemed to be going so well.
I think the harder concrete is more brittle.
Easily fixed by adding fiber and mesh.

 

Check out my fumed silica test took 4 shot to fail.

 

Here is my flawed 5k crack resistant concrete sample.
I put too much water in it and it developed a crack during curing.

 

I got the schmidt hammer.
My 1:1:2 house mix and the "5,000psi mix" are showing about 3,100psi on the schmidt hammer test.
This is much better than the "3,000psi concrete" I mixed up. It's not even registering.
So now we know you and I can mix up good "5,000psi concrete" much cheaper than buying it buy the bag.
You would need about 60 bags to make 1 yard, the 5,000psi mix costs about $6 per bag after sales tax. Which would come to about $360 per yard.
Depending on how many sacks of Portland cement per yard go into 1:1:2 mix I'm thinking 7 or 8 you could be looking at a total price of around $200 per yard depending on how cheap you can get sand and gravel.
Since you are looking at $100 to $120 per yard in Portland cement.

 

I have been thinking about it and with the Schmidt hammer maybe I should try and see if I can make harder and harder concrete using admixes like super P, fly ash and fumed silica that is also still practical and useable that anyone can do. The hardest concrete I could make would use about a 0.25:1 water to cement ratio by volume, then even with waterms reducer it would have to be worked like rammed earth then left to damp cure forever and a day.
Problem is that doesn't work in most applications.

Also continue finding out what works best for cost effective reinforcement.
I have a feeling the primary and secondary reinforcement duo of nylon and fiber glass will work really well.

Then combine the best reinforcement with the hardest concrete.

 

This is the double fiber sample made with unenforced 4,000psi concrete where 1lb per yard of nylon and 1lb per yard of fiber glass.

Here it is after 2 shots on top of each other.


Here it is after 4 shots, not bad seeing how 3 shots were real closer together.

I also have my house mix 1:1:2 mix and Styrofoam concrete mix to test today.

 

Here is the 1:1:2 mix.

The damage isn't as isolated a's my 5,000psi mix or my 4,000psi mix with additional cement and aggregate.

After 2 shots.

This smaller crater is more what I'm used to with harder mixes.

After 4 shots it failed.

What I like about this sample is I actually didn't use enough concrete. This samplease was close to 1.5 inches thick not the standard 1.75 inches thick.
This sample did very well.
Next up the 4,000psi mix plus Styrofoam.

 

I tested the Styrofoam sample, it failed exactly like a control sample, it just released some Styrofoam beads when I blasted it apart.

 

Well you could always precast ballistic concrete into faux stone.