What Mix Should I Use For The Strongest Possible Conrete?

c.c.co.

This is not for a jobsite but for making atlas balls. These balls are used for strength training and get dropped a lot and sometimes on hard surfaces. I plan on adding fiber but what mix do you guys recommend for a very strong and hard atlas ball? A premixed conrete like maximizer with some extra portland?

Tscarborough

Mild steel or cast iron?

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jgray152

I can't say I know everything about concrete but when I build my retainer walls, I use strictly portland cement and sand. When I order it I order a 9-10 sack mix and this concrete, after 7 days of curing, is extremely strong! I couldn't tell you what the exact ratio is from the concrete companies since they keep that a well kept secrete for some darn reason. All I can say is possibly using a 1:1 ratio of clean sand and portland, you should be close. This is what I use when I have to mix my own mix. (This home made mix has not been core tested)

There was a guy that took a core sample of the same type of mix from a redi-mixed company (not from my walls) and it cored out at around 10,000 PSI from what I hear. I was not there personally nor did I see the core sample sheet but that's what I was told.

Using an 18lb sledge hammer is whole lot of work when trying to break 4" of concrete that has been undermined using this mix. Its not lightweight by any means and is very strong.

I hope this helps you get pointed in the right direction if not answering you question exactly.

The main trick when wanting very strong concrete is to mix it VERY DRY!
Here is a video that I helped with from StoneMakers Artisans. A couple parts in this video you can see how try the mix is. In fact, it was slightly to wet for what we do, but this is roughly how dry you want your mix. In fact dryer would be better.

I have heard mixed comments about fibers in concrete, whether or not that actually help the strength of concrete. I would not add fibers to a ball of concrete.

What would the diameter of these balls be?

genecarp

Extra portland will weaken the concrete, just use sakrete crack resistant it is about 5000psi. how do you plan on forming the balls?

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c.c.co.

Those are some conflicting opinions. Diameter is something like 16 or 20". My buddy ordered some molds for making the atlas balls.

jgray152

No conflicting opinions I see. Portland does not add strength, sand and aggregate add strength. Sakrete or another brand of high strength concrete should work well. Just make sure not to add to much water as that will weaken the concrete.

genecarp

Im with you J, keep the water content low, use counterflow, a plastisizer to keep the concrete flowing with low water. G

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Tscarborough

So you plan on making 186# to 360# concrete balls to train with? I would certainly plan on them hitting the ground frequently, as well as breaking off various body parts.

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shanekw1

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jgray152

Probably may not even need counterflow since he is only making balls. I would imagine that as long as you fill the mold little by little, packing it as you go to reduce trapped air bubbles, you should be good.

concretemasonry

The manufacture and quality of the molds will be important.

How you cn fill them is also very important.

As little water as possible, gradation control and variable vibration on a table and being able to change the orientation while compacting will be a big plus. You may have a "nub" left at the filling point that will have to be ground off.

If you do not account for the settlement and compaction if you want maximum strength. Under controlled conditions, you should be able to get 8,000 - 10,000 psi with the right aggregate gradation. If you just pour a typical wet mix, it wet, you will only get 3000 to 5000 psi, no matter what "goop" you dump in.

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Dick

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CJKarl

Add aggregate to non-shrink grout. That's what I would do.

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user50444

I like the steel idea + with a rubber like coating or concrete + with a rubber like coating. A little cushion for damage to the balls + the surface it's going to be getting dropped on.

neolitic

Just have these guys find a mason
and hire on as hod carriers.

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concretemasonry

I also like the idea of a steel core (in a joking way - ).

Can you imagine what happens when you drop a heavy ball with a high density core covered by a few inches of resilient rubber? If could be great entertainment like watching an uncontrolled huge golf ball bouncing and rolling around. - Much bigger and heavier than a bowling ball (3 to 5 times heavier) and more unpredictable.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

c.c.co.

Great info, thanks y'all. The mold is coming from the guys that have made plenty of these and train with them a lot. So it sounds like mix dry, pack often and I was already thinking of using my 1/4 sheet sander to vibrate the mix to get rid of bubbles. Sounds like just a crack resistant premix from the depot will work.

Tscarborough

I still find it hard to believe that you train with 184# and 360# balls. What do you do, roll them around the yard?

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lukachuki

I agree with TSC! Train what, how, and why?

I'm guessing pack mules, pack llamas or possibly packing camels!

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Less with the jaw more with the paw!

c.c.co.

I'm not sure where you are getting these estimated ball weights but my training partner said the first one will be 175lbs then get heavier after we perfect the construction. We are making them to lift from the floor and place on stand kind of like a deadlift or a clean and jerk type of exercise. Strongman competition style.

Tscarborough

4/3*pi*r^3=volume of a sphere

for r=8:

2138.64

2138.64/1728 (Cubic Foot) = 1.24 X 150 (weight of CuFt of Concrete) = 186 #'s

For r=10:

4178.33/1728 = 2.42 x 150 = 363 #'s

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