Mixing concrete is a basic skill that all DIY enthusiasts should know how to do. Concrete is one of the most common and inexpensive building materials on the planet, mostly made up of sand, gravel, and cement.
Mixing concrete is similar to baking in the oven in that for consistent results it is best to follow a specific recipe. There are a multitude of different concrete mixes for different applications depending on the strength, workability and application of the concrete.
Mixing concrete is really a science for the pros, but for the average garden enthusiast, learning the basics of concrete is enough to get you started.
When mixing concrete, you will need to mix aggregates such as sand and gravel with cement powder and water as a catalyst to begin the chemical process of binding the ingredients together. The concrete mix is a function of the proportions where you will measure the volume of aggregate used versus the volume of cement used.
The most common concrete mix used in the world is the 3-2-1 mix which uses three parts gravel, two parts sand and one part cement. Water is added with the idea that you should use as little water as possible to make concrete workable for what you need. The viscosity of concrete is measured by “sag” which refers to a specific test where the amount that a cone deposited with concrete will lose its shape after the cone is removed is measured in inches or mm. Concrete without sag would be very stiff and dry and prone to hold its shape, whereas concrete with sag of six inches or more would be extremely wet and reluctant to hold shape.
The 3-2-1 mix is so widely used because you can fill large areas with concrete for a relatively low price. You could use only sand and cement, not gravel, to create what is called mortar. In the 3-2-1 mix, the gravel serves as a filler, taking up a lot of space while maintaining a relatively high overall strength. The downside to the 3-2-1 mix is that larger gravel aggregate will often float to the surface during finishing and is not suitable for thin or detailed concrete applications.
The best overall mix for a DIY enthusiast to memorize and use is a simple 3: 1 mortar mix. Using three parts sand and one part mortar, you can create the strongest concrete possible as well as easy concrete. to be finished and detailed with drawings, templates or stamps. By not using gravel, the mortar will have a smoother overall consistency, but ultimately occupy less volume than concrete made with gravel. If you’re pouring very large volumes of concrete, gravel can pay off, but for most DIY projects, a 3: 1 mortar mix is the way to go.
The sand you should use for a 3: 1 mortar mix should be sharp sand, masonry sand, or joint sand. Each place you buy sand will use a different term, which can be confusing when shopping. All you need to remember is to avoid playing sand. Play sand is sand that has been washed and sterilized (that’s okay) and then tumbled to soften all the edges of the individual sand grains (that’s bad).
The sharp edges of the sand help hold the concrete mix better than the rounded edges of tumbled sand. Ideally, you would like to find sand at landscape supply stores that will sell you by the cubic yard. With a strong trailer, you can pick up as much sand as you might need for next to nothing – and the quality of the sand for making cement will be very high.
The applications for a DIY enthusiast to use a 3: 1 mortar mix are huge. Everything from repairing broken exterior steps and stairs, walkways, patios, decks, ponds, waterfalls, artificial rock, statues and much more is possible with a simple mixture of sand, cement. and water.
Start with small, concrete projects to gain a better understanding and understanding of how to work with concrete. Since concrete is so popular around the world and is a very advanced science, you will never be short of great real-world applications to discover or try out. Besides being the most affordable building material on the planet and readily available anywhere, learning how to mix basic concrete recipes is a fundamental DIY project.