In concrete drilling for large, industrial projects, there are two common types of concrete encountered: reinforced and non-reinforced. It’s important to understand that each type of concrete requires certain conditions for drilling, and you will see different results for each. A steel bar supporting reinforced concrete, for instance, will strain the diamond bit in a unique way while drilling, resulting in a particular pattern of wear on the cutting surface
Working with Non-Reinforced Concrete
The process of drilling non-reinforced concrete requires that stress be put on the comparatively brittle material using the diamond of the diamond bit. Doing so will produce cracks in the concrete in a process known as crack propagation.
Once cracks have formed in the concrete, you will begin to see pieces of material break away allowing for deeper drilling into the non-reinforced concrete. An indicator of progress in crack propagation is the collection of swarf or concrete chips during drilling. These pieces of broken concrete will be irregular and rough due to the brittle break of the material.
Drilling into Reinforced Concrete
For reinforced concrete, the drilling process relies on an alternative method. Due to the tougher nature of reinforced concrete, a drilling job of this kind will take longer at greater expense compared to allied materials and non-reinforced concrete.
To drill into the steel of reinforced concrete, the drill being used will be set to “machining mode” as opposed to crack propagation, and diamond crystals are used as the cutting device. Similar to drilling non-reinforced concrete, this process will produce visible swarf as a by-product. In this case, however, the chips will be curled steel particles.
The diamond cutting surface used for drilling reinforced concrete will be put under a lot of strain, as the material encountered is comparatively deformable and tough. Conversely, the material surrounding the steel bars in reinforced concrete is brittle in comparison, leading to differences in loading and unloading on the diamond cutting surface of the crystals and bond material.
Greater degradation due to the tougher nature of reinforced concrete leads to a shorter life of the diamond core, and the speed of the drill is slower during drilling of this material. Depending on the concentration of steel in reinforced concrete and the depth of cut, the life of a diamond core bit for a range of applications can be limited by up to 50%.
An indicator that you’ve hit a steel element of the material is the production of sparks. At this point, the operator should lower the speed of the drill and rate of coolant. The RPM of a drill will determine how many times the core bit penetrates steel in a minute, and a greater RPM will result in greater bond matrix degradation and the increased risk of fracture.
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