The chemical anchors represent today one of the best solutions for the construction, recovery and strengthening of new and existing buildings.
The large use of this type of anchor in the fixation and strengthening works is given by the fact that the chemical anchor is the only anchor suitable for use in basic materials such as concrete, solid or perforated masonry, wood, aerated concrete and gasbeton.
This flexibility of use is given by the load transfer mechanism, which occurs by adhesion in the case of solid materials and mechanical interlocking (by using a special plastic or metal cage) in the case of hollow material.
Unlike mechanical dowels, therefore, no compression is transferred on the base material, and therefore the use can also be made in more "brittle" materials compared to concrete.
Bossong S.p.A, a manufacturer of chemical and mechanical anchors, proposes the use of BCR EPOXY21 epoxy resin.
The BCR EPOXY21 epoxy resin is equipped with two different ETAs (Qualification documents):
ETA-11/0344 for the use of resin with threaded rods on cracked and non-cracked concrete.
Seismic qualification in category C2, for diameters M16, M20 and M24.
The main applications are the fixing of metal structures on concrete elements, such as the connection between a steel beam and a concrete pillar.
- ETA-11/0345 for the use of resin with improved adhesion bars for diameters from φ8 to φ32 on concrete.
The main applications are the typical castings between structural elements such as foundations - beams-columns-walls and floors.
From the description of the two qualification documents it is possible to see how both ETAs refer to fixing on concrete.
Up to now, in fact, there is no guideline that specifies test protocols to obtain a seismic qualification of an anchor in case of fixing on masonry.
In the case of restoration and consolidation interventions, it is however very probable that work must be carried out on masonries that may be of different types, such as for example:
1. Stone masonry
2. Solid brick masonry;
3. Half-empty brick masonry;
4. 5. Solid masonry with presence of voids inside.
In all these cases the use of the chemical anchor is the only possible solution.
Also in this case the BCR EPOXY21 epoxy resin is suitable for use in masonry, always guaranteeing the breaking of the base material and never the pull-out of the anchor (the maximum capacity of the system is always reached).
The typical works that are carried out through chemical resins in the case of use for recovery or consolidation are the following:
Creation of a new cooperating slab through the use of plugs connected to the old floor with epoxy resin (a technique often used in the case of old buildings with wooden floors);
- Creation of clamping between orthogonal load-bearing walls;
- Connection between parallel load-bearing walls by means of special chains;
- Concrete slab-curb connection.
- Connection between new wooden beams and concrete curbs;
All these structural applications can only be carried out with chemical resin, and this is precisely the reason why this product is particularly used in works on masonry buildings.
