In our Concrete Drilling Guide Part 1, we discussed the differences between working with reinforced and non-reinforced concrete. This month, we’re following this up with a part 2 where we’re going to be looking even further into the different types of concrete, their strengths and how this can all affect the drilling process.
Concrete age refers to the curing time once a concrete has been poured and laid down. This can largely affect the preciseness of the drilling and the way a diamond core bit can penetrate the concrete. The curing time can also be influenced by other factors including, temperature, moisture levels, the time of year, as well as the general composition of the mixture i.e. aggregate and sand.
This is in relation to the early stages of the concrete, whereby it has not fully hardened or bonded with the mortar. The green concrete only occurs between the first 6 to 48 hours after being poured; and when cutting, the sand easily loosens, creating more abrasion on the blade and requires hard diamond bond.
Following the green concrete stage, cured concrete develops once the concrete has been left to set for at least 48 hours. This means the sand has now totally bonded together with the mortar and is completely hard.
Different types of aggregates can impact the hardness of the concrete, especially as it can make up as much as 75% of the volume. The larger the aggregate, the harder the concrete, therefore making drilling slower. Similarly, the smaller the aggregate, the softer the concrete, allowing drilling to be much easier and speedier.
Steel reinforcing concrete
A concrete’s hardness can also be determined by the amount of rebar that is reinforced on the concrete. The general rule is: the more rebar, the harder the concrete will be.
Like slag, limestone and coral, asphalt is soft yet abrasive, so does not cure and harden as concrete does. The type of aggregate in asphalt is small but has no impact on the cutting, and almost as soon as the asphalt has been rolled out, it can be cut. Due to its abrasive nature, undercut protection is very important. This is where a segment of the blade works to slow down the undercut process, making the procedure safer and it also increases the longevity of the blade too.
Brick and block
Concrete brick is hard and less abrasive, whereas concrete block is soft and abrasive. The hardness of bricks and blocks is determined by a combination of the clay mixture, method of manufacturer and the firing temperature.
To summarise, the overall drilling process can be influenced by a number of factors, such as the aggregate type and size, and whether there is reinforcing steel present.