Whether you are planning on re-paving your driveway, installing a footpath, building a concrete patio, or even making a plant box, the one thing that these common DIY projects is that they all involve concrete. By definition, concrete is the combination of a binder which is cement, fine aggregates such as sand, and coarse aggregates like gravel. But even though you know what makes up the composition of concrete, that does not mean you can create an effective concrete mixture just by guessing what amounts of which ingredients goes where. There is actually a concrete mix ratio, a recipe if you will, that ensures that the concrete you create is as strong enough for your intended purposes. Otherwise, you could end up with concrete that is too brittle, or too dense, for your needs. This error, depending on your specific task, could prove to be catastrophic in the end.
Cement – This is the binding material that attaches all of the other components in the concrete altogether. There are different kinds of cement being manufactured today, but for ordinary household DIY projects you will mostly be using Ordinary Portland cement, or OPC. You may also come across white Portland and masonry cement is some projects as well.
Aggregates – The aggregates are the components that actually give body and strength to the entire concrete mix. Fine aggregates include sand and fine pebbles, while coarse aggregates include large pebbles, rocks and gravel. You will always use coarse aggregates when mixing concrete, the size of the coarse aggregates you need to use will depend highly on how you will be using the concrete; if you are planning on exposing the concrete on extremely high compressive forces, like a driveway, then you need to use larger size diameter aggregates like gravel for the job.
Water – The cement needs water to activate and start hardening. You need to use just enough water to complete wet all the cement in the mix, put too much and the concrete will take a long time to dry and cure, put too little and there will be patches of unmixed cement and gravel in between the concrete which will greatly decrease its strength.
Why is the Concrete Ratio so Important?
It is not enough to just mix random amounts of cement, sand, gravel and water when creating concrete. You need to follow a specific ratio of ingredients if you want to make the concrete mix as strong as possible. There are several problems that will arise if you do not follow the concrete mix ratio, namely:
ñ Making the concrete brittle because you used too much cement. Sure, concrete becomes extra hard if you use lots of cement, but this also makes it fail a lot easier if subjected to compressive stresses.
ñ Making the concrete weak by using too much gravel. If you use too much gravel in the concrete you use for paving your driveway, you will notice that after some time has passed that the gravel is starting to surface. There is not enough sand and cement to cover the gravel on top of the concrete pavement, this makes for a very rough surface.
ñ Using too much concrete not only makes the concrete prone to immediate and rapid failure, it also makes the concrete mix too expensive. You can actually make better concrete just by using the right amount of cement, using too much is just a waste of cement.
Following the correct concrete mix ratio not only ensures a strong end product, it also saves a lot of money.
Basic Concrete Mix Proportions
The type of concrete mix ratio you use depends on how what you are planning on using it on. Here are some of the basic concrete mixes that you can use on your DIY concrete projects.
General Purpose Concrete Mix Ratio
- 1 part cement
- 2 and a half parts of sand, and
- 3 parts gravel.
You can use this type of concrete mixture for most kinds of concrete works like paving driveways, creating pathways and sidewalks, and other general landscaping works.
High Strength Concrete Mix Ratio
- 1 part cement
- 2 parts sand, and
- 3 parts gravel.
This concrete mix proportions is perfect for making ponds, elevated plant boxes, and similar projects because this particular mix of concrete produces a water tight end product that allows only a limited amount of water to seep through.
Mortar Mix Ratio
Concrete is not only used for laying down slabs, it can also bind bricks and hollow blocks together. The concrete mixture that goes in between each brick is known as mortar. And unlike regular concrete, mortar does not contain any coarse aggregates.
- 1 part cement, and
- 5 or 6 parts sand
Creating your Own Concrete Mix Design
There are special cases wherein the two previously mentioned concrete mix ratio is not suitable; you need to create your own concrete mix design. But unless you are a trained and licensed civil engineer, you will never find the process of creating a custom-made concrete ratio is never easy. If you are terrible at crunching numbers, then you should just use an online concrete mix ratio calculator.
To use concrete mix ratio calculators you only need to provide a couple of details about the area you are using the concrete on, like how much weight you are expecting the surface is going to bear? The humidity of the place, how high you need the concrete slab to be, and other details. Once all the details gets punched in, the calculator will then give you a precise concrete mix ratio that is suited for the job at hand.
These online calculators are often found on different DIY websites.
Concrete Mix Ratio
Mixing concrete is not a simple task as you might previously have thought; if you want the concrete you make to last for as long as possible you need to accurately measure the amount of each concrete component. Using too much or too little of any one ingredient will result in a lackluster concrete mixture. This is why when making concrete for your DIY project, you need to follow the concrete mix ratio designed for that specific project as closely and precisely as possible. Otherwise, you’ve wasted your time, money and effort on something that will probably not last as long as you’d hoped.