Most people outside of the construction industry do not realize that concrete comes in various strengths. These strengths are gauged according to a PSI rating. PSI stands for pounds per square inch, and refers to how much weight the concrete can safely support. For most construction jobs, including driveways and sidewalks, 4,000 PSI should be used. Although there is a 5,000 PSI concrete product on the market, 4000 has become the industry standard. Making the concrete is a very simple process, once you have the required ingredients.
Calculate the cubic volume of concrete you will be pouring. This is important because it is what tells you how much concrete mix to purchase. Measure the cubic feet (or cubic inches) of concrete you will need to pour by measuring the length of the area, the width of the area and the thickness of the concrete slab you will be making.
Purchase as many bags of concrete mix as you need to complete your job. You can look at the instructions on the bag to see how many bags are needed for the volume of space you calculated in the previous step. The main thing is to make sure the bag is labeled 4000 PSI. Concrete typically comes in 3000 PSI, 4000 PSI and 5000 PSI, so it is important to get the right mixture.
Read the instructions on the brand on concrete mix you purchased to see if extra materials should be added. Some manufacturers may ask you to add sand or even gravel to the mix. If so, purchase the amount of material recommended by the manufacturer. Most ready mix concrete formulas require nothing but water, so that is generally all you will need.
Determine where you will mix the concrete. If it is a small job requiring one or two bags, then you can get by using a shovel and wheel barrel to mix everything. This works well for many home projects or light patching. If it is a larger project requiring several bags of concrete mix, then you will probably want to rent a concrete mixer to make the job easier.
Read the instructions on the concrete to determine how much water is required. This will vary from one brand to the next. Add the recommended amount of water and mix well. If the instructions called for other materials in Step 3, those should also be mixed into the concrete at this time. Once all ingredients are mixed well, the concrete is finished and is ready to be poured.
Never mix bags of concrete from different brands. This will create inconsistencies in the mixture. You will get better results if you use all one brand of concrete mix. Similarly, do not add 3000 or 5000 PSI into your mix. If you are mixing 4000 PSI concrete, then every bag should be 4000 PSI.