Strongest concrete mix

[men8ifr]

How do I get the strongest concrete mix - Is there a stronger mix that the 'strong mix' on the bag?

If I mix concrete with water only will that be as strong as possible?

I also need to drill through whatever I make so can't have it diamond like...

 

[PrenticeBoyofDerry]

What strengths are you after and what purpose of use?
If the blend is too strong it will cause shrinking and cracks to appear.
A neat mix of cement and water, would be no good, as you do need larger aggregates to help give the mix strength.
A mix used in foundation would be comprised of 1 cement, 2 sand or very fine aggregate, and 6 coarse aggregate.

 

[Static]

You can go upto about 100N/mm2 concrete cube strength nowadays.. which even superman would struggle to break.. as the above asks, what use are you thinking?

 

[ban-all-sheds]

Oh you can get harder than that - over 220N/mm² commercially available.

http://concreteproducts.com/mag/concrete_lafarge_introduces_psi/

Good luck drilling it though.

And if you want to push the boundaries of what can be achieved:

Wired.com reported on April 13, 2007 that a team from the University of Tehran, competing in a contest sponsored by the American Concrete Institute, demonstrated several blocks of concretes with abnormally high compressive strengths between 50,000 and 60,000 psi (340 and 410 MPa) at 28 days.[3] The blocks appeared to use an aggregate of steel fibres and quartz – a mineral with a compressive strength of 160,000 PSI, much higher than typical high-strength aggregates such as granite (15,000–20,000 psi or 100–140 MPa).

Reactive Powder Concrete, also known as Ultra-High Performance Concrete, can be even stronger, with strengths of up to 116,000 PSI (800 MPa).[4] These are made by eliminating large aggregate completely, carefully controlling the size of the fine aggregates to ensure the best possible packing, and incorporating steel fibers (sometimes produced by grinding steel wool) into the matrix. Reactive Powder Concretes may also make use of silica fume as a fine aggregate. Commercial Reactive Powder Concretes are available in the 25,000–30,000 psi (170–210 MPa) strength range.


Are you building a nuclear bomb shelter or something?

 

[men8ifr]

It's for 2 things, first as part of a wall render to which a heavy duty hinge will be mounted on and second to mount a lintel on top of a wall but it needs strength to stop teh wall moving at the top due to the weight of a (v.heavy) door

 

[JohnD]

if you want to get it really strong, you don't need a fancy mix. Excess cement makes it shrink and crack. Voids are the enemy of strength.

just,

use a well-graded aggregate. The idea is that the mass should be solid with no voids. Every stone should be covered in sand, and every grain of sand should be covered in cement, and every particle of cement should be covered in water. Every gap between big stones should be filled with small stones, and every gap between small stones should be filled with sand. The largest stone you can use depends on the thickness of your slab.

no more water than is needed to make it flow into the mould and consolidate. Any extra water will dry out and leave a void. Voids have no strength.

Properly specfied readymix is usally better than you can mix by hand or in a baby mixer.

tamp or vibrate it well to pack down (but not so much that water and cement rise to the surface as a layer of fat)

keep it well moistened with water spray, and wrap it in polythene to prevent it drying out while it cures. It gains strength all the time it is curing. Once it has dried out once, it will gain no more strength, even if you try to wet it again (you will see the colour change)

curing it for 2 weeks will give quite good strength. Strength gain incrementally gets slower and smaller after that.

underground concrete in damp ground is usually especially strong and hard because it never dries out, and some of it may continue gaining strength for many years. By that time, the extra strength per year is very tiny, though. If you compare that to cement render or mortar, which may be dry in half a day unless covered, you will find the quick-dry stuff is very weak and you can scratch it with your thumbnail (yes, I know the mix is different).

Whatever you lay it against must not be so dry that it absorbs all the water

 

[PrenticeBoyofDerry]

It's for 2 things, first as part of a wall render to which a heavy duty hinge will be mounted on and second to mount a lintel on top of a wall but it needs strength to stop teh wall moving at the top due to the weight of a (v.heavy) door

The render wont hold your door, it's the block/brick work, behind it that will do that and if the wall has been built right a normal brick mortar will do, to bed your lintel in, if the lintel is heavy it may need to be packed out to keep your joint at 10mm, using slate or plastic packers.