1. How do I get a rating of 3000 psi on the concrete
2. The area adjacent to the existing driveway is not level (slants away @ +3% grade, what precautions do I need to take?
3. Sand is the content of my soil (90-99%) do I need to create pillars in the sand at each corner, when pouring the concrete.
4. My father-in-law has a cement mixer can we continue to make up new batches of concrete or do we make just enough for each form, then move on?
Cement - 550 lb.
Sand - 1275 lb.
Stone - 1875 lb.
Water - between 250 and 350 lb.
The more water you use, the weaker the concrete.
At 250 lb you will get moderately workable mix with potential strength of
over 4000 psi
At 350 you will be closer to the 3000 psi without much of a safety factor.
To convert these numbers to cubic feet divide them by 27 (I assume your mixer is smaller than a cubic yard)
2. I am not sure what the problem is. Just make sure that water drains away from the finished concrete. If you are concerned about placing the concrete - there should not be a problem unless you add so much water that it starts flowing (and then your strength will go away)
3. I assume you are asking about foundations. Sand (clean) is the best base you can find. It is good practice to make the edges of the slab thicker than the rest (up to double the 4-5" you will be placing). Also make sure the sand is well compacted and moist before you place concrete (so it will not suck water out of your mix)
4. Concrete may be useable for up to one hour after you mix it (depending on the cement) but I would not recommend mixing more than you can place in 15-20 minutes. Remember, it takes time to spread and finish it.
Other important rules to follow:
Separate the slab into sections of no more than 15 feet each side. 10
feet is much better. These joints can be created by cutting the fresh
concrete, inserting plastic joints, forming, or any other creative way.
This will keep it crack free.
Keep the concrete wet for as long as you can. Start by covering it with plastic, wet burlap, or plain sand - and keep watering it for at least 3 days. 7 days would be even better. Start spraying it as soon as it sets - 3-4 hours, but no hard spray. Fogging is best.
Good luck.
I'm realizing how much of a novice I really am!
I found your site by doing a search through metacrawler.com on the key word cement! I live in Colorado Springs, Colorado on the north end of town, number 5 questions was coloring of cement I want to make it look like giant tiles with a burnt orange color (the front yard has decorative rock the traditional black/gold and I wanted to maintain some continuity in the backyard with the "patio"! I do appreciate the info. I was wondering your site mentioned using wire mesh to increase the strength to 3000 psi how or what is the process? Pour the cement then add the mesh or ???
Thanks for all you help!
5. You can purchase Concrete pigments from specialized suppliers. However, getting the right color and making sure it is uniform may be tricky. Good luck...
<I was wondering your site mentioned using wire mesh to increase
the strength to 3000 psi how or what is the process? Pour the cement then
add the mesh or ???>
You probably misunderstood what was said there. Wire mesh does not
increase the strength. What it does is reduce the potential cracking
(which is very important by itself). The strength can only be
increased by reducing the water.
The best way to use mesh is by placing it in the forms on small pieces of
concrete that will keep it about 1-2 inches above the sand. You can
also buy plastic "chairs" for the same purpose at concrete supply location.
Some people simply lay the wire mesh on the sand, place the wet concrete on
top of it, and then try to pull it up into the correct position (which is
about half of the concrete thickness). As you may guess, this is a
very inaccurate method that can lead to problems.
Good luck,