What are cinder blocks made of? Cinder blocks are just plain concrete blocks. They are made up of cast concrete that is a combination of Portland cement mixed with sand, small gravel, aggregate and water. Lower grade and strength blocks can use a higher proportion of sand compared to cement. They can also contain either ash or coal cinders to make them lighter but this reduces their strength. The cinder blocks are lighter than traditional concrete blocks. This allows them to be used effectively in high rise buildings. Very lightweight concrete blocks can also be produced using autoclaved aerated concrete.
They are built in a fashion that allows for iron and concrete enforcing. The iron is usually placed in the hollow spaces in the cinder blocks, and they are then filled with concrete. This make the building and foundation extra hard. Such structures can then easily withstand earthquakes and high intensity winds and tornadoes.
Can you make your own cinder blocks?
Yes you can. You should definitely try to DIY this. Our fore fathers have been doing it for centuries. Just be aware that you don’t go on building houses and rooms with your DIY project without permits. As it can land you in issues. But if you are just making the blocks to make a fence or make a kennel or a garden shed go ahead.
What is the best mix for concrete blocks?
The best mixture for making concrete or cinder blocks is a 4 parts sand to 1 part cement, 1 part gravel and 1 part water ( the 4:1:1:1 rule) . By adding 4 parts of sand to 1 part cement you will make a more structurally strong block. But you can also add 5 parts sand to make the ratio 5:1:1:1. This will make a less strong block but will be cheaper as compared to the one I mentioned above.
You can generally use the later type of block for building walls that wont have to bear the weight of a ceiling (i.e. for fencing) or for making structures that will have a wooden roof. If you will be placing a permanent concrete roof on the blocks a 4:1:1:1 is must.
But you need to check with the local guidelines for the strength of the block they demand. They may even ask to make stronger blocks with a 3:1:1:1 composition. As with any building project, you need the assistance of an architect and a civil engineer to discern what will be the right structural material to use.
You absolutely fine building concrete blocks but if you want to sell them then you would need to get a permit after testing. Similarly you would need to get permits to build a room or a house with your DIY blocks. Do not just blindly follow any guidelines online, including this one. If your blocks aren’t structurally strong enough they can lead to a roof collapse in the event of an earthquake, which can be very dangerous.
There is another formula which is making a cinder block without gravel. This includes 4 parts sand to 1 part cement. It is easier for beginners to start with this as it doesn’t require too many components.
How to make cinder blocks ?
First you would need to make a concrete mold for pouring in your mixture. The best mold will not bend or alter in shape with the pressure and weight of the concrete but will be malleable enough to be easily removed once the block has hardened. If you are gonna DIY, you can get the mold at your local hardware store.
Next you would need to build the mixture of concrete to make the block. You can go with either 4:1:1:1 ratio or 4:1 without gravel ratio. Now just pour in the mix into the mold. After about 5-10 minutes you can remove the mold. It is always a good idea to get 10 to 15 molds so that you can make at least 10 to 15 blocks in one go.
Do not let the concrete mix harden cause it will become as hard as rock in about 30 minutes. Just make enough that would fill all the molds in one go. After you remove the first batch molds you then make a new mixture to make even more blocks. 🙂
Commercial cinder block manufacturers now use a machine that builds the shape of the block and puts it on a conveyer that then places the blocks in sunlight for hardening. So it is a very automated process. If you plan on doing this as a business you would need to invest in one of these machines to make your life a bit easier.
If you are confused about the dimensions and sizes of blocks read this article.
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