Portland cement is the most common and widely available cement mix throughout the world.
It is also the most versatile because you can customize the concrete mixture to fit every project.
As long as you know the correct mixture ratio of cement to sand and/or possibly an aggregate to use, you’ll have the perfect mix.
When it comes to making concrete crafts, there is a perfect recipe of cement to sand. And based on my tests below, the best ratio is 3 parts cement to 1 part sand (3:1).
The differences I was testing for were strength, tactile texture and visible texture when used in making concrete and cement crafts.
Why is any of this important? Why should cement mixing ratios even matter?
Having the correct cement to sand to water ratio will be the main determining reason your concrete crafts project is a success or failure. This large tile planter box is an example of a success.
You will need a mix that you are able to cast into a narrow cavity if you are making a concrete craft.
This means the mix has to be fluid and workable. If the ratio is incorrect, it will either not be workable enough to go into the mold.
Pocket Guide to Concrete & Cement Mixes For Crafts
In order to compensate for this, you will need to add excess water to get it into the mold, which will cause it to crack.
I performed five different tests, using different ratios of cement to sand, as well as percent cement of sand and aggregates to see how they performed.
Okay, so 3:1 is the correct mixing ratio, so I’m good to go, right?
I’ll explain why, in terms of the ratio proportions, you would need to make changes. Don’t worry, the principles are basic and easy to apply, but they are important.
But there are a few important things to understand about portland cement.
First, cement alone cannot adhere to anything. It doesn’t work without the addition of water and a simple aggregate, like sand.
Once these two components are added to cement, a chemical reaction takes place and the cement binds together.
You can increase the strength of the concrete in certain applications through the addition of pea gravel, or larger aggregates like crushed granite, which is a common aggregate.
There are more details about this in my article about the differences between cement and concrete.
You may also be interested in checking out this article about what ratio to use in a hypertufa mix.
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Basic Materials Used For Determining The Best Ratio Of Cement To Sand For Concrete Crafts
- Portland cement
- Play sand (for weight)
- Fine aggregate– play sand
- Small aggregate– pea gravel
- Medium aggregate– sandblasted sea glass
- Large/ coarse aggregate– crushed granite
- Plastic containers
- Plastic cups
I was running a little bit short on both types of larger aggregate material and so I substituted the sandblasted sea glass to have enough for a full ratio for these tests.
The sea glass was a perfect blend of both the small rounded pea gravel and the sharp aggregate from the crushed gravel.
For my sand, I used play sand. This types is a soft sand. It is typical of the kind found in smooth pre-mixed cement mixes. It doesn’t contain any particles other than fine sand.
I decided which ratios I would test based on the actual instructions for mixing portland cement. The official instructions call for a ratio of 1 part cement to 3 parts sand.
The intended use at this ratio is more as a building material.
But having mixed this ratio in the past, I knew this high proportion of sand would be very difficult to work with for general purposes of working with crafts, but it was good to use as a baseline.
The reason 1:3 doesn’t work well with making concrete crafts is that you need a certain amount of fluidity in order to get the cement mixture into your mold.
Typically, our molds have small cavities and so to achieve the desired workability, at a 1:3 ratio you would need to add too much water.
The mixture would be very crumbly and you wouldn’t be able to get it into the mold.
Once you add the amount of water needed to get it into your mold, you will have weakened the mix so much that it would crack.
Click here to jump down to the bottom for a summary of the results.
Otherwise, read on for the details and steps taken in the cement recipe experiment below.
Mixing Cement: The Ratio of Cement To Sand
For each test I followed the same steps, except for the varying of the ratios.
The cured concrete pieces that were made to test each cement mixture recipe were pencil holders. I used the same containers to maintain consistency.
*It’s important to know that the thickness of the pencil holders (basically planters without drain holes), had a side and bottom thickness of ⅜”. This is typical of many small to medium sized planters.
The Basic Steps For Each Cement to Sand & Aggregate Ratio Tested:
First, I mixed the dry portland cement powder together with the dry sand. You should mix the dry ingredients together first for a well-mixed, smooth consistency.
Next, I added a small amount of water and mixed the ingredients together. I continued to add more water until I had the consistency of a wet mud pie or very formed brownie batter.
Then I added the mix to the plastic cup, and set a timer for two minutes and vibrated it by shaking it and tapping it on my work surface. I also tapped the sides of the container.
After the two minutes were up, I placed an inner mold inside the container. I then vibrated it for another 20-30 seconds and then set it aside to cure for 24 hours.
Test 1. 3:1 Ratio Mixture Of Portland Cement To Sand
Three parts of dry cement powder mixed together with one part dry sand.
Mixture Workability Notes:
This felt very similar to my typical go-to mix, which is a pre-mixed cement mix called Cement All.
Cement All is a smooth mix and forms very easily without requiring much water to have good workability.
The high cement ratio may have made it feel just slightly smoother than Cement All, but so similar.
Test 2. 2:2 Ratio Mixture Of Portland Cement To Sand
Mixture Workability Notes:
This cement mixture was easy to form but, with the high amount of sand mix, the cement mixture retained a lot of air.
This cement mixture has too much air in it due to the high proportion of sand, which traps air.
Test 3. 1:3 Ratio Mixture Of Portland Cement To Sand
One part dry cement with three parts sand.
Mixture Workability Notes:
This was not a workable mix for making concrete crafts. I needed to add too much water to make it less crumbly.
For the amount of water I ended up adding, I was concerned I risked making the cup holder weak.
Also, when vibrating this, a foamy, ice slurry appeared on top. I was curious to see if this would affect the texture or look of the cured piece.
Test 4. 2:1:1 Ratio Mixture Of Portland Cement To Sand To Gravel
Two parts cement and one part sand, mixed with one part gravel.
Mixture Workability Notes:
This concrete mix ratio was surprisingly not difficult to form, but it was heavy with the amount of gravel and sand.
When vibrating it, it took over 1 ½ minutes for bubbles to start rising to the surface, unlike each of the others, where the bubbles appeared typically early on.
Test 5. 3:1 Ratio Mixture Of Portland Cement To Gravel
Three parts cement mixed with one part gravel.
Mixture Workability Notes:
This reminded me of the same texture as Quikrete’s Quick Setting Cement which felt like heavy clay. It was so dense that it was a little less workable than some of the other ratios.
The Cement Mixture Recipe Giving The Best Results
Test 1. 3:1 Ratio Results
A ratio of three parts cement to one part sand was smooth and the color was consistent. There were almost no pinholes present.
Test 2. 2:2 Ratio Results
Using a two parts cement and two parts sand ratio had only slightly more pinholes than the 3:1 ratio, but showed slightly more variation in color.
Test 3. 1:3 Cement Ratio Results
The one part cement to 3 parts sand ratio had a lot of pinholes, and some minor blotchiness in color.
Test 4. 2:1:1 Ratio Results
Using a ratio of 2:1:1 of 2 parts cement to 1 part sand and 1 part gravel was a pleasant surprise.
It had a mottled appearance which I expected and is often a desired visual outcome since it has a more concrete appearance than cement.
But despite the mottling, the overall color was consistent. It had almost no pinholes.
Test 5. 3:1 Ratio Results
The ratio of 3 parts sand and 1 part cement was, as expected, a bad ratio for making cement crafts.
The appearance was mottled, but the color was a bit blotchy around the piece. There was a decent amount of pinholes.
Summary of The Testing For The Best Ratio Of Cement Crafts Ratio To Sand:
The results show that the best ratio to use is 3 parts cement and 1 part sand when making small cement crafts.
This will result in a smooth, consistent appearance and give you the ability to easily vibrate any entrapped air. This ratio provides plenty of durability for a craft this size.
However, each of the ratios tested did result in a durable, fully intact cured piece.
But the one part cement to 3 parts sand ratio (1:3) wouldn’t have worked if I hadn’t added more water, or if the cavity that it was cast into was narrower. This is not a good recipe for concrete crafts.
If you desire more of a concrete appearance, with slight mottling, use a ratio of 2 parts cement, 1 part sand and 1 part gravel.
Quick Facts On Cement Mix Ratios
- Sand increases the amount of entrapped air
- Aggregates in mix will increase air pockets
- Trapped air that isn’t sufficiently vibrated will show pinholes
- Higher sand proportions and gravel-types of aggregates will require more vibration time
- Too much sand, gravel or both reduces workability and usually requires adding more water, weakening the mix.
- For a smooth surface, your safest bet is to use less aggregate and or smaller/smoother aggregate in your concrete mixture ratio.
When To Change The Cement Mix Ratio For Concrete Crafts
A general guide for a good recipe for medium-duty (or medium-sized) concrete crafts projects is (2:2) at 2 parts cement and 2 parts sand.
The concrete mix ratio for a heavy-duty project like large planters should have a higher proportion of aggregates.
The important factor is the durability required because these will require thick sides and bottom.
For this, the ratio should be (1:3) 1 part cement to 3 parts sand, or (1:1:1 or 1:1:2) 1 part cement, 1 part sand, and 1 or 2 parts aggregates.
Remember, for maximum strength in the resulting concrete, always use the least amount of water that still allows for good fluidity.
You can read more about how to choose the best mix for your project here.
This will help you understand more with recipes and about working with the premixed bags of cement that are available at most North American home improvement stores.