Concrete cosmetics - repairing exposed concrete for high demands
Flawless exposed concrete surfaces with concrete cosmetics
Sichtbeton wird in der modernen Architektur nicht nur aufgrund seiner statischen und konstruktiven Eigenschaften eingesetzt. Exposed concrete surfaces also look good. However, this is only the case if the surfaces are flawless. Chipped edges, discolouration, scaling, cracks and other flaws disrupt the desired appearance. Concrete cosmetics for exposed concrete provide a remedy here and restore the perfect visual impression of the building materials.
Any remedial work on concrete needs to be carefully planned. The first step is to assess the actual condition of the concrete surface. Based on the damage pattern, it is determined which cosmetic measure can be carried out promisingly and economically. Products such as putties are used particularly frequently, localised defects are corrected via filler materials. Colour changes can be corrected by using paints, glazes or cosmetic putty.
Also part of concrete cosmetics are various protective and impregnation measures for the surface such as anti-graffiti protection, hydrophobising, oleophobising or biocide treatment. The surface protection should be renewed regularly to maintain the appearance of the concrete.
Concrete cosmetic measures are often required to eliminate workmanship deficiencies in concrete as a building material. In this case, it must be checked in advance whether the result contradicts the tender or the specifications of DIN 182020 and 18217. In this context, it should be noted that imperfections in exposed concrete are often unavoidable. A position for necessary repair work on the visible surfaces should therefore be included in the tender.
From an expert’s point of view, a distinction is made between three variants, which colloquially all fall under the term “concrete cosmetics”:
- Concrete cosmetics means the correction of concrete defects using special fillers.
- Concrete retouching refers to the elimination of colour differences such as marbling or cloud formation by means of colour pigments.
- Colour glazes create or match colour tones. The exposed concrete character is retained with this treatment.
Exposed concrete is divided into four classes, each with different visual requirements. The classifications range from SB 1, fair-faced concrete with low requirements, to SB 4 concrete surfaces with particularly high design significance. Depending on how the fair-faced concrete was put out to tender, any cosmetic retouching that may be required counts as remedying a defect or must be accepted by the client as unavoidable.
Various exposed concrete deviations cannot be avoided 100 %; furthermore, various requirements cannot be produced accurately:
- A uniform colour tone of all elevation surfaces cannot be guaranteed, but differences in colour and texture caused by incorrectly stored formwork are avoidable.
- Low pore formation can be achieved by using absorbent formwork or self-compacting concrete.
- Bleeding and edge chipping can be minimised by proper execution, but not completely prevented.
In many cases, flaws in exposed concrete can be eliminated by filling. This is the actual field of work of concrete cosmetics. The proven method is used, for example, for cosmetic treatment of the following imperfections:
- Washed out formwork joints
- Concrete ridges
- Wavy concrete surfaces
- Deviations from the overall impression
B.T. Innovation offers various concrete fillers in different grain sizes for filling exposed concrete, for example the MC Fix, which can be used to effectively level edges and misalignments.
For the defect removal to be carried out perfectly and effectively, a clean and dry substrate is required. For maximum absorbency, the concrete surface is pre-wetted before troweling; a bonding bridge matching the trowel is recommended as a substrate. Depending on the layer thickness, the filler is applied in one or more layers using the wet-on-wet technique. For flawless trowel results, a timely after-treatment must be carried out to prevent too rapid evaporation due to wind or sunlight.
Colour differences, rust stains and various discolourations also disturb the harmonious overall impression of an exposed concrete surface. As a cosmetic measure, the use of paints and glazes as well as cosmetic spatulas can be considered here for beautification. With the help of specially matched pigment mixtures, the desired renovation colour tone is achieved and the concrete surface is unified by this type of exposed concrete cosmetics. The glazes are applied as needed and in several layers. When applying paint, ensure that the concrete character of the visible surface is maintained.