Anchors whose operating principle is mechanical interference, such as concrete screws, allow for rapid installation. In addition to this, since they do not have any expansion element, they can be removed just as easily. This has led the market to highlight the reusability of these products as one of their main advantages. While we can accept the veracity of this claim, there are certain aspects that must be considered before reusing these products.
We will use an INDEX THE concrete screw to show all the aspects to be considered in this regard. When installing the product for the first time, the product installation instructions contained in the European Type Approval (ETA) and in the product data sheet must be followed.
Among the aspects to be considered in relation to the reusability of this type of product, the most important is that once the product has been installed for the first time, it cannot be removed if we want to maintain the performance guarantees established in the ETA. In other words, any reuse of the product, even in the same hole, cannot guarantee the resistance values established in the aforementioned INDEX technical documentation.
So why would anyone risk reusing the product?
In many cases, anchors are used with structures that are exclusively subject to compression stress to fix them to the ground so that they are not dragged or moved by external agents. In these situations, anchors are not working in any way since they are not undergoing tensile or shear stress.
In these cases, and for temporary installations, users may prefer to reuse a concrete screw, which will allow them to reuse the anchor on numerous occasions and, after removing the product, will also leave a clean and open surface as no elements protrude.
Were they to use a bolt-through anchor in the same situation, not only would it not be possible to remove the product once expanded without damaging the base material, but the threaded part of the shaft would protrude and be a hindrance.
In any case, users carrying out this type of installation must be aware that in no case will these installations be covered by the parameters established in the ETA and that the anchor is not subject to any of the stresses mentioned or they are negligible.
So, can I reuse the concrete screw as many times as I want?
The answer to this question will always be NO! The second most important aspect to keep in mind when reusing these products is that each time they are reinstalled, their thread gets worn and loses diameter each time it is reused. This has a direct impact on the properties of the product, dramatically decreasing its performance, especially its tensile strength.
If I can´t reuse the product as many times as I want, can it be guaranteed to withstand at least 3, 7, 15 reuses? Unfortunately, as there are no European regulations governing this matter, we cannot clearly state how many times a product like this can be reused. In addition, it must be considered that the number of uses depends directly on factors such as the power of the tool used, the strength of the concrete, the quality and distribution of its aggregates and the skill of the installer. Among these factors, the strength of the concrete is particularly important. The reuse of the product in low-strength concrete will always lead to a higher number of uses, while for high-strength concrete this number may be limited due to the faster deterioration of the thread. It is advisable to visually check the product before each reuse.
In conclusion, the most important aspects to consider are:
- Always follow the instructions in the ETA and the technical documentation
- Reuses are not covered by the ETA
- Reuse the product if the fixing is not subject to tensile or shear stresses
- The product cannot be reused an unlimited number of times
- Visually check the product before each reuse
Latest revision: FAQ13 rev0
