5 Tips for Avoiding Concrete Cancers When Putting in a Concrete Wall
If you want to minimise the risk of concrete cancer in your cement walls, you need to have strategies in place as you put in the wall. There are a few different ideas that can help.
1. Avoid Magnesium Oxide Boards
When making your concrete walls, you can use plywood, fibre cement sheets, or a range of other materials to support the concrete. Ultimately, you smear the concrete onto these materials, and it sets to become your wall. If possible, avoid using magnesium oxide sheets, the magnesium can draw moisture out of the surface of the concrete wall and lead to cancers.
2. Reduce the Absorption Rates of the Supporting Materials
Typically, fibre cement sheets, plywood, and other materials are absorbent, and their hygroscopic nature can increase the risk of cancers. To explain, essentially, when you apply the concrete to the boards, it is wet. Then, as it dries, some of the underlying boards absorb some of the water. This phenomena throws off the balance of water and concrete, and ultimately causes dips in the concrete.
If you have to use a supporting material that is particularly absorbent, make sure that you take steps to reduce its absorbency. For example, if you use plywood, you can cover it with a bit of oil to stop it from absorbing water.
3. Consider Using a Waterproof Barrier
Instead of trying to make the supporting materials less absorbent, you could cover the supporting boards with a waterproof barrier. For example, some builders paint on an epoxy. Then, they let it dry, and they apply the concrete on top of that.
4. Cover Metal Components Well
When metal bars or or other bits of metal are too close to the surface of the concrete, that too can lead to cancers. To ensure you avoid this risk, make sure that you adequately cover the metal with a thick layer of cement. The exact amount depends on the type of concrete you use and the building codes in your area.
5. Eliminate Air Gaps Around Metal
Unfortunately, if air gets into the metal framework, the metal may start to rust. You can prevent this from happening by eliminating air gaps. Essentially, you want a very tight fit between the concrete and the metal.
For example, if you are applying concrete mix, use concrete with a high slump level. That makes it more manageable and easier to work around the metal.