How to Mix Concrete Properly
Given the reliability and versatility of concrete, today it is an indispensable building material in almost all kinds of structures. This wonderous mix is used in many kinds of building work from constructing heavy supports to making building blocks. Therefore, it becomes mandatory for any constructor to know how to mix concrete properly – the methods, the tools, the pitfalls.
Concrete is basically a mix of cement, sand, and large and small stone chips that are called aggregates, mixed with water to form a gel that hardens over time to form an extremely powerful solid that is sometimes sturdier than the stones used in it.
Changing the quality and ratio of these materials, the concrete gains different characteristics like being able to harden very fast or to increase load-bearing capacity. Even the way you apply the concrete changes its character.
A perfect mixing method is also necessary to make good concrete. If the mixing method was not proper, it may get too liquid or too dry, may become brittle after solidifying, may be susceptible to weather effects and so on. Needless to say, proper tools (and machines) are needed to do the job correctly. Let’s see how you can perform concrete mixing the right way, for small projects that don’t require heavy concrete trucks or ready-mix deliveries.
Tools and materials used for concrete mixing:
1. Bags of cement
3. Small stone chips (10 mm)
4. Large stone chips (20 mm)
7. Cement mixing tub
8. Clean water (not drinking quality, but clean enough)
10. Mixing tools
11. Stiff-bristle brush large
12. Protective gear (dust mask, rubber gloves, long boots) - this is needed because the cement used in concrete is a caustic material and can cause chemical burns on skin, or worse problems if it gets into eye or lung.
Method of properly mixing concrete
Step 1: Gather your equipment and materials
Get the tools and clean them thoroughly – it is undesirable to use dirty tools in a fresh mixing. Sharpen the hoe a bit, too. Next, buy the materials (cement, sand and stone chips) as per your intended concrete ratio. For general purpose, it’s something like 1:1.5:3, but of course you may need some other kind of concrete. Make sure you buy some extra materials to allow for wastage, 2% is normal.
Step 2: Add cement
Take a clean mixing tub or mixing wheelbarrow, and set a bag of concrete in it firmly. Slice open the bag near the bottom using the sharp side of the hoe so that the cement can get out. Now pull the bag off slowly so the cement stays in the tub.
Step 3: Add sand and aggregate
Pour the sand in the tub and mix thoroughly. Next, do the same with the aggregate. Make sure you are pouring them in the right ratio!
Step 4. Reserve
Take some of this dry mix out of the tub and put it in another container. You’re going to need it for adjustments later.
Step 5. Measure water
Read the instructions on the cement bag about how much water it needs, and also consider how much your specific type of concrete needs (you may need a more dry or wet mix for your purpose). Figure out exactly how much you need for the materials in the tub now. Then, measure that amount of water and set it aside.
Step 6. Add the water
Push the dry mix on one side of the mixing tub or the wheelbarrow. Now, pour the measured amount of water, slowly, to the other side. Keep a little water in reserve for later adjustments. It’s better to be drier than soupy.
Step 7. Mix the concrete
Using the hoe, pull small portions of the dry mix into the water and stir it till its evenly spread out. Keep doing this until all the dry mix is caught in the water. Keep stirring in large swaths till the mix has an even texture all around.
Step 8. Test and correct
Do a slump test to see if the concrete mix has the characteristics are exactly what you need. If the test result fails to meet your expectations, use the reserve dry mix and water carefully to adjust the mix according to your need. Unless you are using a kind of cement that solidifies very, very slowly, you won’t get many chances to do this again. So, make sure you get this step right in one iteration, and quickly.
Step 9. Final stir
When you’re sure that the mix is good, give it a few more rapid stirrings with the mixing tools till you get a very smooth mix with no puddles or lumps.
Step 10. Clean up
Clean the tools and the mixing tub/barrow immediately after use, or let them soak in water. This is because once concrete hardens, it gets very difficult to remove – as it should be. Dry the tools after cleaning as well.
All done! Now you’re ready to mix the next batch.