A new star has “risen” over a former barrack complex in the northwest of Augsburg in Bavaria. The Urban Star is a large, star-shaped sculpture made from colorful, illuminated concrete blocks that offers space for people to sit, relax and interact. Most of the cubes are made from concrete through-colored with inorganic pigments manufactured by the specialty chemicals company LANXESS. Twenty-four of the cubes are made from translucent concrete, inside which colored LED lights are embedded. During daylight hours, the sculpture’s appearance is characterized by the colored cubes, with the translucent concrete then becoming increasingly prominent as twilight approaches.

“The structure is built to last, and the desired color effect is designed to be enjoyed for many years to come. This is why we decided to use iron oxide pigments, which are known to remain color-stable over decades and can withstand whatever the weather throws at them,” says Oliver Fleschentraeger, Market Segment Manager Construction in the Inorganic Pigments (IPG) business unit at LANXESS.

Urban district planning: Kobelcenter-Süd

The Augsburg urban development society acquired the former barrack complex, which was used by the US armed forces up until 1994, as public trustee for the city of Augsburg and has been gradually turning the land over to civilian use. The development project aims to create a mix of commercial and residential properties with plenty of green space and good links to neighboring construction areas. The urban development area Kobelcenter-Süd on the former barrack complex is one such quarter that will see a mix of commercial and residential properties. In addition, green spaces are home to the kinds of flora usually found on the North American prairie, helping to lend this new quarter its own identity.

The “stars” and plants recall the many years during which the site was used by the Americans and the cultural mark they made. They encompass elements of American landscapes and legends, representing a contrast with the site’s use as a functional residential and commercial area. Various usages are envisioned. The “Urban Star” is a place for meeting people and relaxing, linking the barrack complex with the urban space; the “Desert Star” is a multi-generational recreation area; the “Dark Star” a habitat for jackdaws. More stars will be added in future construction phases, each with their own specific purpose and character.

Vivid colors by day and night

The publicly accessible “Urban Star” is located at the center of a district plaza that covers around 800 square meters. The block-like structure of its cubes and the color scheme of the concrete surfaces are reminiscent of the downtown urban landscapes typically found in the west of the USA.

The colored concrete cubes are pigmented with weather-resistant, colorfast, inorganic pigments from LANXESS’ tried-and-tested Bayferrox brand, with black, red and yellow being the dominant colors; a cobalt-blue pigment developed by Recklinghausen-based Harold Scholz & Co. GmbH is also used. The black, translucent-concrete cubes manufactured by Aachen-based LUCEM GmbH and also pigmented with Bayferrox pigments consist of translucent-concrete panels measuring around two centimeters in thickness.

The blocks measure 84 x 84 cm and, in keeping with the sloping topography of the plaza, rise between 14 and 60 cm above the ground. The concrete cubes are designed with a flat, pyramid-shaped pitch on their surface, which prevents water from accumulating and minimizes the risk of ice forming in the winter. In combination with the concrete cubes, the light-gray, artificial-stone paving used on the plaza helps to create a harmonious overall aesthetic.

The “Urban Star” is secured to the ground by means of a 25-centimeter-thick, reinforced-concrete baseplate, which projects by around 10 centimeters and follows the outline of the star. The baseplate lies on a foundation bed that was compressed layer by layer. A solid, step-like substructure for the colored concrete cubes and made from standard concrete was mounted on the reinforced-concrete plate. The surface of the concrete has been specially waterproofed. The concrete and translucent-concrete cubes are mounted onto the substructure with drainage mortar and, at the edges, directly onto the baseplate. Drainage mortar in combination with step drainage ensure that any water beneath the concrete cubes is properly drained away.

Inorganic pigments for long-lasting structures

LANXESS is the world’s largest manufacturer of synthetic iron oxide pigments and one of the leading producers of chromium oxide inorganic pigments. The Inorganic Pigments business unit has extensive expertise in the production and handling of pigments and processing in concrete manufacturing. “The technical service offering comprises extensive analyses regarding the colorimetric and physical pigment characteristics as well as their influence on concrete-related and rheological characteristics in customer-specific applications, which can be simulated under laboratory conditions,” says Fleschentraeger. “This is why we collaborate closely with raw material producers, plant manufacturers, architects and universities.”