Mixing concrete is a lot of work, yet sometimes it is the only way to get that small amount you need for a planter or repair around the house. The first thing you need to know is what type of concrete you are going to need for that project you have in mind. There is post mix, sidewalk mix and several other varieties, all with different ratios of ingredients. All have differing stress levels and strengths. Basically there are only a few different varieties normally offered in the bags. Although the basic ingredients are the same the size and amount of gravel changes as does the sand and the proportion of Portland cement that holds it all together. Some special jobs require mixing your own concrete from scratch, mixing the ratios of ingredients on the spot. Do not purchase straight Portland cement or sand by mistake, Portland cement by itself has no strength and will fall apart.
I will not be going to delve deeply into each as no one building a skyscraper will be coming here to see about mixing it up. A simple bag of sidewalk mix is sufficient for our needs. Contact your local supplier if you are doing a large project as they have the knowledge to recommend the right product for the job.
Figure out how much concrete you are going to need, buying one more bag than you figured on since you can’t easily add concrete after the fact. Figure the square inches by multiplying length x height x width then convert it to cubic feet by dividing it by 1728 and finally to cubic yards by dividing again by 27. The bags will be marked by the yard as that is how concrete coverage is measured, you have to read the fine print, but somewhere it will tell you how many bags to the yard.
Pour the bag or part of it, if you only need a small amount, into a five gallon bucket or a wheel barrow. Add small amounts of water and stir it with a shovel, adding water until the concrete is damp evenly through out. The consistency will be like a thick milkshake though lumpy. Too dry and it will crumble when cured, too wet and the top will scale off. Be sure not to leave any dry spots in the mix.
Mix only what you need at one time, or if you need more than a single bag mix them one at a time to be sure they are thoroughly mixed. One bag of concrete can be 80 lbs. add water to that and it gets heavy fast, using a wheelbarrow will help save your back. If you have to move it very far from the mixing site and if the forms you are using are large enough you can pour it right out of the wheelbarrow, saving even more work.
Concrete can be colored to suit and will form most any shape you can imagine, even natural rock.
Properly cured concrete will harden for around one hundred years. Concrete doesn’t actually dry out, it hydrates or takes on water as it cures and can harden even under water. It is also one of our most versatile building materials and is capable of being able to withstand the stress of being made into a high rise building when encasing steel.