What use is the anchoring

Standard-compliant anchoring of facades

Concrete as a problem?

A big and frequent issue is that the anchoring ground deviates from the set of rules. Lightweight concrete is often used in today's buildings. Lightweight concretes are concretes with light aggregates such as pumice, expanded slate or expanded clay with a low bulk density of between 800 kg / m³ and 2,000 kg / m³. Lightweight concretes are divided into four different categories: dense lightweight concrete with grain porosity, aerated lightweight concrete, pore-like lightweight concrete with dense or porous aggregate and aerated concrete.2

The structurally dense lightweight concrete is regulated in DIN EN 1992-1-1 with a corresponding national annex and in DIN EN 206 / DIN 1045-2. In the regulations of fastening technology you will find lightweight concrete in vain. In the case of structurally dense lightweight concrete, such as that used in load-bearing walls and ceilings, there is a closed structure between the components of the building material. Therefore, in principle, all anchors / dowels that are otherwise also suitable for fastening in concretes of strength classes C20 / 25 to C50 / 60 can be used. Adhesive anchors should preferably be used. The anchor should be approved for cracked concrete so that it works sufficiently safely. Anchoring in lightweight concrete usually results in approval in individual cases (ZiE). For this purpose, usage reports that have already been drawn up can be consulted if the framework conditions, e.g. B. the strength of lightweight concrete, are comparable.

Not only lightweight concretes can be found in construction projects, but also concretes that are outside the range of “normal strength” concretes, i.e. between C20 / 25 and C50 / 60. In new construction projects, concretes that do not correspond to normal concrete are used in over 10% of cases.3 Planning documents with old concrete designations such as B15 or even B225 from DIN 1045 published in 1960 can often be found in the renovation area and in existing buildings Not. Strictly speaking, such a conversion is not possible, as concrete grades are explicitly defined in the regulations. However, since these relate to the respective strength, these conversion tables are generally accepted in fastening technology. Fischer also provides such a conversion table. Accordingly, the low-strength or high-strength concretes that are outside of ETAG 001 or the corresponding European Assessment Document (EAD) require special consideration, as these basic documents only take into account concrete grades from C20 / 25 to C50 / 60 when it comes to individual fastenings. There is an exception for multiple fastenings of non-load-bearing systems. A frequent application of this multiple fastening is in substructures on walls and ceilings. Concrete quality C12 / 15 is already defined in these regulations.

DIN EN 1992-4, which will soon be introduced by the building authorities, tries to close the gap in concrete quality outside normal concrete. With this standard it will be possible for the first time to anchor anchorages in accordance with the standard. The standard will also take into account concretes whose strength is in the range from C12 / 15 to C90 / 105 and which are regulated in accordance with DIN EN 206. However, fiber-reinforced concrete is excluded. In future, values ​​for low-strength and high-strength concretes will also be included in the assessments after the corresponding EADs have been adjusted.