How do you correctly make concrete? The amount of cement and aggregate required depends on the intended use of the concrete, as it’s not the same whether you’re pouring a sidewalk, a parking area, or a load-bearing column. When is it worth buying pre-mixed concrete in bags? What size gravel (aggregate) should be used for different concrete applications?
One of the questions that is difficult to find a clear answer to on the internet is – how to make concrete. Of course, here we are talking about making concrete for your own needs, when you need to pour a path in the yard, build a small wall, or something similar.
Buying Ready-Mix Concrete in Bags
For small quantities, concrete can be mixed by hand in a large tub or bucket, but for larger projects, a concrete mixer is necessary. At the outset, it’s worth mentioning that if you’re working on smaller projects, like making planters, small pillars, decorations, and similar items, you can buy ready-mix concrete in bags.
You simply mix it with water according to the instructions on the package, and the concrete is ready to use. The advantage of this option is that you get a mixture of proven quality and composition, free of impurities like pieces of wood, shells, or clumps of dirt.
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These impurities usually float to the surface after pouring, and as they decompose, they leave holes where they were. The downside to buying ready-made concrete is that it’s generally the most expensive option, making it suitable only for very small projects.
How Do I Mix Concrete Myself?
If you want to make your own concrete, you will need cement, gravel (aggregate), and water. The most debated topic is how much of each to put in the mixer. You can avoid these debates by simply reading the preparation instructions printed on every bag of cement.
For the least demanding concrete structures, such as sidewalks around the house, you should use five and a half shovels of gravel for every one shovel of cement in the mixer. For the foundations of smaller structures or concrete driveways that will support vehicles, use four and a half shovels of aggregate for every one shovel of cement.
For more structurally demanding concrete elements, like concrete slabs, beams, or columns, use only four shovels of aggregate for every one shovel of cement in the mixer.
Depending on the amount of cement in the concrete mix, there is a noticeable difference in its texture. You can easily see when the concrete is richer in cement or when it is leaner, as builders often say. The amount of water should be adjusted so that the mixture is neither too runny nor too thick.
Which Aggregate Should I Use?
The choice of aggregate also plays a significant role. It’s advisable to use washed aggregate, meaning aggregate that has gone through a separation process to remove impurities.
For smaller projects, like pouring planters or making concrete decorations, it is recommended to use so-called “unit” aggregate, which is finer and sieved. For rougher work, coarser aggregate is sufficient, provided it is of good quality and clean.
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