I have been doing some small scale experiments to determine what individual items or addtives can be added to concrete to make it more damage resistant compared to a control sample with no modification.
And surface treatment that can be applied to existing concrete.
The concrete used is just quikcrete 4,000psi mix, with the recommended amout of water.
All samples are 11.7x11.7 square and 1.75 inches thick and left in the forms for 3 days and left to cure for a month.
I selected this test size and 22mag test gun as a universal standard that is cheap to test and should scale up.
Because I don't know what you are trying to build, what your local building code's are, I don't know what the design your engineer signed off on looks like. I don't know if you are just trying to fill in a concrete block wall voids, if you constructed the forms your self and have added mesh or if you called in a concrete truck and can only add in some fiber before they pour.
These improvements can be used on anything from a tornado shelter to a tornado proof house.
I'm just trying to find a few options to make a better structure or maybe just a better concrete counter top.
I noticed most people's idea of a test is just shoot a wall. Well that really doesn't tell you any kind of useful information.
The test gun is a bolt action 22mag with a 20 inch barrel from about 2 feet away, striking perpendicular.
Larger thicker samples and bigger guns just cost exponentially more and tell me the exact same thing.
At some point I will make larger samples and hit them with larger center fire rounds, but not today.
So far what I have found is most additives and mix modifications do nothing.
Going out of your way to remove air is a waste of time. I tested vacuum and vibration concrete, which helps remove air, these samples did worse than the control.
I also tested polymer strength booster. It helped a little. But at a cost of an additional $150 per cubic yard it's not worth it.
I am about to test fumed silica. But I believe that it's results will be a lot like the polymer strength booster, a lot of added cost for a minimum improvement.
The 2 things I tested that seemed to help a lot was any kind of chopped fiber and any kind of mesh, even plastic mesh.
Plastic mesh should cost about $7 per layer, per yard for a 4 inch wall and allowed my samples to take twice as many rounds before failing over the control.
Stucco mesh just under the strike face did even better. The stucco mesh retained the material that had been blasted loose, and normally would have been blasted away, held it in place and disrupted incoming rounds. A very unexpected result.
The stucco mesh costs about $25 per layer, per yard in a 4 inch wall. Good news is you only need one layer, the much cheaper $7 per yard plastic mesh performed just as well in back side and internal layer tests.
Chopped fiber should cost less than $20 per yard and dramatically increased damage resistance.
Since the reduced air entrapment samples failed so bad I am going to try to increase air entrapment. I just made a sample with the equivalent of 1 pound of Styrofoam beads to 1 yard of concrete.
Each pound of Styrofoam per yard should increase air entrapment by nearly 1%.
The added cost of Styrofoam is between $20 to $50 per 1%, per yard. A chemical air aid addtive should be cheaper.
In the next few days I want to do a 4,000psi and 5,000psi control sample shoot out and see if the added cost of going to 5,000psi concrete makes a difference.
Shredded rubber added to the mix, because why not?
I have super plasticizer to test, it allows you to make concrete with less water, less water makes stronger concrete.
For an added cost of $20 per yard I should test it.
Any other addtives or mix modification recommendations?
And surface treatment that can be applied to existing concrete.
The concrete used is just quikcrete 4,000psi mix, with the recommended amout of water.
All samples are 11.7x11.7 square and 1.75 inches thick and left in the forms for 3 days and left to cure for a month.
I selected this test size and 22mag test gun as a universal standard that is cheap to test and should scale up.
Because I don't know what you are trying to build, what your local building code's are, I don't know what the design your engineer signed off on looks like. I don't know if you are just trying to fill in a concrete block wall voids, if you constructed the forms your self and have added mesh or if you called in a concrete truck and can only add in some fiber before they pour.
These improvements can be used on anything from a tornado shelter to a tornado proof house.
I'm just trying to find a few options to make a better structure or maybe just a better concrete counter top.
I noticed most people's idea of a test is just shoot a wall. Well that really doesn't tell you any kind of useful information.
The test gun is a bolt action 22mag with a 20 inch barrel from about 2 feet away, striking perpendicular.
Larger thicker samples and bigger guns just cost exponentially more and tell me the exact same thing.
At some point I will make larger samples and hit them with larger center fire rounds, but not today.
So far what I have found is most additives and mix modifications do nothing.
Going out of your way to remove air is a waste of time. I tested vacuum and vibration concrete, which helps remove air, these samples did worse than the control.
I also tested polymer strength booster. It helped a little. But at a cost of an additional $150 per cubic yard it's not worth it.
I am about to test fumed silica. But I believe that it's results will be a lot like the polymer strength booster, a lot of added cost for a minimum improvement.
The 2 things I tested that seemed to help a lot was any kind of chopped fiber and any kind of mesh, even plastic mesh.
Plastic mesh should cost about $7 per layer, per yard for a 4 inch wall and allowed my samples to take twice as many rounds before failing over the control.
Stucco mesh just under the strike face did even better. The stucco mesh retained the material that had been blasted loose, and normally would have been blasted away, held it in place and disrupted incoming rounds. A very unexpected result.
The stucco mesh costs about $25 per layer, per yard in a 4 inch wall. Good news is you only need one layer, the much cheaper $7 per yard plastic mesh performed just as well in back side and internal layer tests.
Chopped fiber should cost less than $20 per yard and dramatically increased damage resistance.
Since the reduced air entrapment samples failed so bad I am going to try to increase air entrapment. I just made a sample with the equivalent of 1 pound of Styrofoam beads to 1 yard of concrete.
Each pound of Styrofoam per yard should increase air entrapment by nearly 1%.
The added cost of Styrofoam is between $20 to $50 per 1%, per yard. A chemical air aid addtive should be cheaper.
In the next few days I want to do a 4,000psi and 5,000psi control sample shoot out and see if the added cost of going to 5,000psi concrete makes a difference.
Shredded rubber added to the mix, because why not?
I have super plasticizer to test, it allows you to make concrete with less water, less water makes stronger concrete.
For an added cost of $20 per yard I should test it.
Any other addtives or mix modification recommendations?