If you want to make a concrete pillar, you can do that with a cardboard tube. Basically, you just pour the concrete mix into the tube, let it harden and remove the tube. To ensure the final effect looks as nice as possible, you may want to keep these tips in mind.
1. Make Sure to Use a Tube Designed for This Purpose
Ideally, you should only use a tube that is designed for this purpose. for instance, you may want to use a Formatube rather than a plain cardboard mailing tube. The latter doesn't offer the stability you need, and ultimately, with a subpar tube, you may end up wasting the concrete and not creating the look you want.
2. Choose the Right Shape
The first decision you need to make is about the size of your Formatube. To ensure you get the size you want, you may want to find a pillar that you like and measure its circumference. Then, if your tube matches that size, you know that you're getting the correct size.
Also keep in mind any embellishments you want. For instance, if you don't want a smooth pillar, you may need a tube with curved edges. Similarly, if you don't want the pillar to have any lines from the inside of the cardboard tube, you need to choose a tube that has a smooth finish.
3. Use Rebar to Stabilise the Concrete
While setting up your Formatube for the concrete, you may want to add some rebar. This helps to strengthen the pillar, and it ensures that it will last longer. Have someone hold the rebar in place as you pour in the concrete. Otherwise, if you let the rebar just sit loosely in the frame, it will end up being slanted in the pillar.
4. Have a Disposable Container for Your Concrete
When you're finally ready to mix your concrete, consider using a disposable container. You can just throw those away. If you are using a container that you need to clean, you may end up accidentally rinsing some concrete down your drain. Even if you clean the container with a hosepipe outside, you may end up getting bits of concrete into your grass or the storm drains.
5. Let the Concrete Dry
Finally, once you pour the concrete, make sure to let it dry thoroughly before you remove the cardboard tube. To speed up this process, you may want to do this on a day that is dry and relatively humidity free.