Portland Cement Challenge

How about adding a solid section of 4140 steel?

Homework answers are not allowed in the rules of CR4 but....................

Here is a gentle push -

http://www.cibofnyc.org/CIB%20Articles/09-03%20Econ%20High%20Strength%20Concrete.pdf

I am confused as to what the requirements of the cylinder are - is it 3" diameter, does the cylinder have to be 6" tall and hold 10,000 psi, do you even need the cylinder? .................

Will half a pound of cement even make a 3" dia x 6" long cylinder?!?!?!

What is going on?!?!?

It must completely fill the cylinder and can only set for 7 days. We put it under a press, to see how much psi it withstands.

My guess is random fiberglass strands mixed with the cement.

Suggestion, (just for a bit of fun) get a cylinder of suitable engineering material 2.9" x 6" and fit that into the mould. I'm guessing that steel would probably suffice, then fill the intervening gap around the perimeter with cement.

There may be minor surface cracking, but the internal cylinder will hold up the the parent material performance and if you've chosen correctly then 10,000 psi should be no problem.

You need the 3" diameter to hold roughly 31.5 ton (at 2240 pounds to the ton) You can find the material.

I've seen what most people would call re-bar that was 75mm OD, so there might be a 3" version in the US and fill the gap around that with mortar using the cement.

by using a matrix or composite the result is stronger than cement alone, without cheating with rebar, two things spring to mind: gravel which is conventional but still good, or rusty steel mesh producing ferrocement but I don't know how long that takes to cure properly. If you report back we will know for the future.

Well it seems we are in the same boat, my friend. We are unable to use rebar, obviously that wouldn't be much of a challenge. We thought about scattering individual fiberglass threads throughout the mix, we also thought about using kevlar mesh. Only thing is, we weren't sure if these things would perform under compressive stress. I did get a random idea today, though... anyone have an opinion about aerogel? It supposedly has high compressive strength... but I don't know if the amount of air it contains would bring down the strength of the original mix.

"We thought about scattering individual fiberglass threads throughout the mix, we also thought about using Kevlar mesh. Only thing is, we weren't sure if these things would perform under compressive stress."

What is the difference between embedding the glass or Kevlar threads in epoxy resin, or concrete?