Cooltoren Rotterdam: Building package with precast (exposed) concrete elements

The tower will be constructed largely of precast concrete elements. An entirely individual color was even developed for the fair-faced concrete. This of course requires precise monitoring and control of the concrete composition and the pouring and demoulding process in Hoco Beton's precast plant in Weert. And that for two (!) years.

Text | Roel van Gils  Image | Hoco Concrete

The 150 meter high Cooltoren will soon form one of the tallest apartment buildings in the center of Rotterdam with 282 apartments ranging from 60 to 400 m² and a total area of 37,620 m². The eye-catching white residential tower has a striking and functional silhouette with its center of gravity in the middle. As a wholly-owned subsidiary of main contractor Ballast Nedam, Hoco Beton was engaged for the production of all precast concrete elements. These include large numbers of sandwich parapets, frame elements, balconies, stairs with trees, columns and column discs, elevator cover plates, stairwell walls and much more.

The 150-meter-high Cool Tower will soon form one of the tallest apartment buildings in the center of Rotterdam.

Cool Tower White

The balconies, sandwich parapets and frame elements deserve special mention. After all, they determine the appearance of the Cool Tower and are executed on the visible side in aesthetic concrete. "For all visible sides, we determined the unique white color in consultation with the architect (V8 Architects), our cement supplier Aalborg and dye supplier Cathay Industries," begins Gerard Goedbloed, concrete specialist at Hoco Beton. "It involves a composition of Aalborg White (white cement) to which, among other things, dye (0.5% Ton Pierre) is added for breaking up the white color, as well as Ferrotint White F31 (4%), a titanium dioxide pigment for the self-cleaning effect of the fair-faced concrete. We very appropriately christened the warm white color Cool Tower White."

The tower will be constructed largely of precast concrete elements.

Concrete waits for no one

Developing the color is one thing, keeping the composition as consistent as possible is two. "We do that extremely well," says Goedbloed. "Thanks also to the high quality of the dyes and the constant grind fineness (blain values) of Aalborg White. Our role is then to keep the water/cement factor constant, as well as the demoulding cycle. After all, the latter also affects the color. We therefore write continuity and repetition with a capital letter in our concrete plant. It is important to do the same thing every day. All variables are closely monitored, including the outside temperature. Even during the heat wave, the pouring process continued as usual. By playing with the admixture superplastic (Cugla), depending on the outside temperature, we ensure continuous flow and processing time - also called open time. After all, concrete waits for no one."

By playing with the admixture superplastic (Cugla), Hoco Beton ensures a continuous flow rate and processing time of the concrete mixture depending on the outside temperature.

Just after the summer break of 2019, the first elements for the Cool Tower were poured at Hoco Concrete. Since then, at least six elements have been produced every day. "In terms of prefabrication, we follow the construction process quite closely  and have little slack in time. So in terms of planning, we can afford little stagnation. We expect to be busy for another year with the production of all precast elements," concludes Goedbloed.