Anchors with the operating principle of mechanical interference, such as screws directly for concrete, allow a quick installation. As well as this, given that they have no expansion elements, they can be uninstalled with the same ease. Because of this, the market has highlighted their reusability as one of the main advantages of these products. Although we can consider this statement true, there are certain aspects that must be taken into account before reusing these products.
Let’s take VBT’s TLE concrete screw to illustrate all the aspects to consider related to this issue. First of all, whenever the product is installed for the first time, the product installation instructions on both its own homologation (ESR-4314) and the product’s technical data sheet must be followed.
Among the aspects to take into account regarding the reusability of this type of product, the most important is that once the first installation of the product has been carried out, if we want to maintain the performance guarantees established in the ESR, it cannot be uninstalled. In other words, any reuse of the product that is carried out, even if this takes place in the same hole, cannot guarantee the resistance values stated in the VBT technical documentation mentioned above.
So why would anyone risk reusing the product?
In many cases, anchors are used to fix structures to the ground that are working exclusively under compression with the sole purpose of preventing them from being dragged away or moved by an external agent. In these situations, the anchor is not working in any way given that it is not subjected to any traction or shear actions.
In these cases, and for temporary installations, the user may prefer to reuse a concrete screw that will not only mean that the anchor can be reused on numerous occasions, but also, when the product is uninstalled, it will leave a clean and clear surface as there will be no protruding element.
If a male anchor is used in the same situation, not only will the product not be able to be uninstalled once expanded without damaging the base material, but the threaded part of the shaft will protrude, making it an obstructing element.
In any case, a user who carries out this type of installation must be aware that it will under no circumstances be covered by the parameters established in the homologation and that the fixing is not subject to any of the actions mentioned or that these are negligible.
So, can I reuse a concrete screw as many times as I want?
The answer to this question will always be NO! The second most important point to take into account when reusing these products is that every time the product is reinstalled, its thread is damaged and decreases in diameter as it is reused over and over again. This directly influences the operation of the product, drastically decreasing its performance, especially tensile strength.
If I can’t reuse it as many times as I want, can it be guaranteed to last for at least 3, 7, 15 reuses? Unfortunately, since we don’t have any standards that regulate the matter, we are unable to categorically say how many times a product like this can be reused. We also have to take into account that the number of uses depends directly on factors such as: the power of the tool used, the resistance of the concrete, the quality and distribution of its aggregates and the skilfulness of the installer. Among the factors mentioned, the resistance of the concrete is especially important, as reusing the product in low-resistance concrete will always promote a higher reuse number while, by reusing it in high-resistance concrete, this number can be limited as the thread is damaged more quickly. It’s a good idea to check the product visually before each reuse.
In conclusion, the most important aspects to consider are:
- Always follow the instructions in the ESR and the technical documentation
- Reuses are not covered by the ESR
- Only reuse the product when the fixing is not subjected to traction or shear actions
- It can’t be reused an unlimited number of times
- Visually check the product before each reuse
Latest revision: FAQ13 rev0
