Concrete is a mixture of portland cement, aggregates, and water. The amounts of each one will affect the formulation of the concrete. This is why concrete is available in different grades. To pour a concrete sidewalk, you should aim for a 4,000 psi formula. Psi stands for pounds per square inch. This is not the weight of the concrete, but how much weight a square inch of that concrete can withstand. Concrete surfaces such as sidewalks, patios, and porches require much heavier concrete compositions than structures not subjected to foot traffic.
Measure the length and width of the area where you will pour the sidewalk in inches. Multiply these two numbers together, then multiply the resulting number by 4, as 4 inches is the standard minimum thickness for a sidewalk. Divide the final number by 12 to find the cubic feet of concrete you will need.
Visit a hardware or home improvement store and read the packaging of the available ready-mix concrete. Locate concrete labeled 4,000 psi and examine the label, since it will tell you how many cubic feet one bag will fill. Purchase enough bags of the same brand of concrete to fill your sidewalk, rounding up if necessary.
Rent a concrete mixer large enough to hold the amount of concrete you need. Transfer the dry concrete mix to the barrel of the mixer. Add the amount of water directed by your brand of concrete, since this will vary.
Turn on the concrete mixer and allow the barrel to rotate at least 70 times. This not only mixes the concrete but also traps necessary air in the mixture. The concrete is now ready for pouring.