Most people are not aware of the significant carbon impact that the production of cement has. Production of cement accounts for 5% of the worlds carbon. This is a significant figure for what seems to be an innocuous product.
Because cement plays such a significant part in the construction of any building , if one is to truly build green, then it is important to look at ways to reduce the amount of cement used.
And one of the biggest users of cement in construction is in the manufacture of concrete. Greener concrete suppliers have now started to deal with this issue but supplanting cement content with a product called fly ash. Fly ash is a by-product from the burning of coal and makes an excellent substitute for cement. By using fly ash in concrete, what has previously been seen as a waste product now has become a valuable asset.
For this project we have used concrete from a supplier who has replaced a portion of the cement content with fly ash, significantly reducing the carbon footprint of the concrete we have used.
Because we intend to leave the concrete slab as an exposed element, it is crucial that the concrete is finished and trowelled well. Our requirement was for the concrete to receive a near burnished finish. A burnished finish is when the concrete is mechanically trowelled with a trowelling machine, as seen above, until it has cured sufficiently that the blades of the trowel are almost burning the concrete surface due to the friction of the steel blades on the concrete.
We have used a burnished finish because it provides a durable and hard wearing surface to the concrete as well as a subtle surface lustre.
Lastly, and most importantly is the curing of concrete once it has poured. Curing of concrete is one part of the concreting process that is often neglected. However, without proper curing, all of the earlier effort will be wasted. Curing it the process of preventing concrete from prematurely drying out due to exposure to the sun or wind. If freshly poured concrete is allowed to prematurely dry out, it will fail to achieve its final strength and the quality of the surface finish will suffer.
There are many ways to cure concrete, but the main methods are either the application of a chemical compound to the surface, covering the surface with plastic sheeting or permanently keeping the surface wet. We avoid the use of the chemical compound for environmental reasons and the plastic sheeting because it can mark the finished surface of the concrete. So we use a method of keeping wet hessian rolled out across the concrete surface, as you can see in the image above. Typically concrete should be cured for a minimum of 7 days, with up to 30 days ideal. Given that the finished internal floor will be the exposed concrete, we have chosen to cure the concrete for 30 days to ensure that we have the best quality surface finish.