Next is concrete is rated by its PSI/tensile strength. It comes in rating of 1000psi- Is not used for much.
2000psi- Is used for things like crawlspaces, were all you need is a hard surface, and for small sidewalks.
3000psi- Is your all round stuff. It is used for things like aprons, sidewalks, footings for small walls etc.
4000psi- Is used more for patios, aprons for larger driveways.
5000psi- Is used for roads, driveways and places were hi strengths is needed. IE footings.
6000psi- Is used for highways and small airports and footings.
7000psi- Is used for runways,(not 747 size)Drainage pits, and footings for large walls.
8000-10,000psi is used for runways of big airports. That have to take a big beating.
Next is about it. Concrete by itself is kind of strong, but when you add aggerate in it, and chemicals in it, it becomes even stronger. Like when you go and buy a bag of Redi-mix it has small stones in it.
To make it stronger you can add things like rebar, fibers, more of a ingredients like Portland. One thing that you don't want to do is add a lot of water. Water is not concrete's friend, the more water in the mix you have, the weaker it will be. So when you are mixing add a little bit of water at a time until it gets just enough wet so that it is plyable and it is throughly mixed.

That is too wet.

That is too dry, when it just crumbles.

That is perfect.
Some of the things you can use to reinforce concrete is rebar, and fibers. The rebar comes in many sizes, and shapes. You can add it if you want too, look for some #3 rebar. That would work the best.
Next thing you can add is fibers. Now you can buy them in bags for you, or you can just buy some Nylon sting add cut 3'' long sections of it. And if you do use this, when you are mixing, add them in there a little bit at a time.
Ok that is pretty much it for now on the info part, I will add some stuff later on.
TIME FOR THE MAKING OF THE AMMO!!
Ok fist off you need supply's. Here is a list of what you will need.
1.Water
2.Concrete
3.Something to mix it in, a 5gallon bucket is good
4.Something to mix it with, I used a trowel because I do this for a job, but a small garden shovel will work good
5.Mold, I used 6' of 1 1/2'' sch40 PVC, but it is best to make then no longer than 12'', I will explain later.
6.Some thing to seal the ends of you molds, I used duct tape.
7.Your reinforcing materials, if you want to add them.

Now for how to make them.
Step 1- Making your molds.
First you want to cut all your molds out. Then you want to cover one end with tape to seal it. Be sure to put a few layers on it.

Step 2-Mixing the concrete
What you want to do is put your concrete in a bucket, then add a little bit at a time of water until it looks good. Remember not to add to much water, as this will cause it to become weaker.
Step 3-Filling the mold.
Now take your mold(s) and hold them over the bucket and just start filling, as you are filling, add a little bit a time, and then tap it on the ground a few times, this will take out the trapped air so it will be stronger. And then just keep going until you get to the top.

Step 4- Adding the rebar
It you sued the fibers you should have all ready mixed them. But if you are using the rebar now is the time to add it. Once you mold is about 3/4'' from the top, take your rebar and press it in, and taping the mold at the same time.
Now I used small peases of it, witch I had at work, and I dropped them in as I went along. And I did that too because my mold is 6'.

Step 5-Getting rid of the bubbles.
Now since you have the mold make and the reinforcing materials in, you want to get rid of the air that is trapped inside of it. The best way to do this, is to tap it on the ground for a while, or use something that vibrates. A massager would work good for this.
What I did was put the mold by my foot, and starting at the bottom, hit it with a rubber mallet to the top, and did this for about 10min.


Step 6-letting it cure.
Even tho it has dried, that doesn't mean that it has "cured". The curing time for the concrete I used is 28 days. That is because I used special concrete. But on the bag it will say the cure time on it. Leave it for around 2 days in the mold, and then you can take it out. You could use them right then, but they wouldn't be as strong.
So what I would do is leave them in my house for the time it takes to cure them. This way they are super strong.
Step 7- Removing the mold.
Now I haven't done the steps after this yet because mine is still drying. So I will update this as I do the other steps.
If there is any questions feel free to ask me.