In the last few decades, the building material concrete has developed to an outstanding high technology material. Apart from its original application for static-constructional building components, the continuous further development of the building material has made sure that it moves more and more in the spotlight of architecturally demanding construction works. As is known, concrete does not set limits to the creativity of architects, planners and artists. Precast concrete components perfectly qualify for realizing architectural concrete. Made in high quality, they normally have the quality of fair-face concrete. For Hemmerlein it always comes first to orientate on the individual requests of the customers. For this purpose, the family-owned company has an internal engineering office ensuring appropriate statics and construction. For the surface solutions, processing and treatment of fairface concrete can be divided in seven forms of production. These options are also realized at the precast concrete plant of Hemmerlein in Bodenwöhr. Fair-face concrete surfaces available are:
» smooth
» acidified
» sandblasted fair-face concrete
» fine-washed and rough-washed fair-face concrete
» polished fair-faced concrete
» textured fair-face concrete
» photo concrete

At present, there is a strong demand, in particular, in three categories: polished, acidified and washed. The following projects of Hemmerlein GmbH clearly demonstrate how the results can look like and which additives have been used.

Citygate Basel
At the city entrance to Basel (Switzerland) situated at the former premises of a milk processing plant the office park Citygate is currently under construction. The Swiss architects Diener & Diener have recently completed a sevenstoried office building as the first building of the four-part ensemble there. The anthracite-colored façade of the building with a floor plan covering 70m to 20m is characterized by far protruding floor levels, thus appearing to be monolithic, what looks as if they slide through the homogeneous front of the glass façade. In fact, the parapets and lintels of the continuous window front were dramatically put into the limelight in this way. The elements in full depth colored in an anthracite shade have a smooth polished surface which were subsequently treated with the product Colorfresh of Hebau. This is a concrete impregnating agent with water, oil and dirt repellent properties, which moreover provide a visually silk gloss and color enhancing effect. To ensure a consistent surface despite the large grain size required was especially challenging at this project.

Secondary School Gaimersheim
The surroundings of the new secondary school of Gaimersheim (Germany) are determined by linearity: the Munich-based architects Stefanie Fuchs and Arnd Rudolph consider the farm land, fields and paths all around the estate at Hochholzer Berg as characteristic for the area. According to this, they have developed the school building from an elongated floor plan outline. The linear appearance is even more accentuated by the longitudinal rectangular character of the curtain-type façade made of fine-washed precast concrete elements. In order to achieve a natural stone like appearance, the additive CSE Deactivator of Hebau GmbH was added here. This is a liquid concrete surface deactivator that is applied inside the mold and prevents hardening of the concrete near to the surface when curing in a predefined exposure depth. After demolding the “deactivated” hardened cement paste can be washed out with the aid of a high-pressure washer thus exposing the aggregate structure. The minimum exposure depth of 0.5mm was chosen for this project, which, in combination with the yellowish aggregates selected, gives the concrete surface a precious, limestone-like character. The curtain façade of the new building in a Jura stone shade features some concrete elements with a smooth surface as well as others having a fine-washed texture.

CECAD laboratory building in Cologne
On the premises of the clinical center of the University of Cologne a laboratory building covering a floor space of about 11000 m² is currently under construction destined for the Cluster of Excellence “Cellular Stress Response in Aging- Associated Diseases” called CECAD. This building project is faced with high demands concerning efficiency and functionality. As apart from the laboratories an area of about 3000 m² will be created for keeping animals. Thebuilding is realized according to the planning and design of the internationally operating architectural office gmp. They were able to win the preceding restricted architectural competition for this project with their subsidiary in Aachen (Aix-la- Chapelle). The CECAD is a scientific cooperation between the University of Cologne and its independent clinical center. The building will have an acidified façade, for which the product Microgel of Hebau GmbH will be used. It is a relatively low-viscosity gel with acid ingredients. This is applied to a smooth concrete component after demolding. The gel-like viscosity ensures a consistent application taking the quality of the respective concrete surface into account. Microgel generally only removes the upper cement skin up to a roughening depth of about 0.3mm. In this process, the acid ingredients of the additive react with the alkaline cement paste and neutralize each other not creating any dangerous reaction products. Thus, the concrete surface gets a “precious”, natural stone like appearance. The white acidified curtain façade is furthermore furnished with a negative texture in a dot pattern. This is to illustrate molecules as a symbol of the content of research carried out.
Robert Mehl, Aachen