'Sleek, 'naked' concrete in all its natural beauty'

An interview with Bert Schauwvlieghe, director and project manager of Elbeko.

What does Elbeko stand for?

"Elbeko is a general contractor and construction promoter, founded over 50 years ago by my grandfather. We focus on the residential market. Thanks to our know-how and consistent pursuit of quality, we are in what you could call the top and subtop segment. Our projects are located almost exclusively in Antwerp, East and West Flanders and Flemish Brabant. Elbeko has about sixty employees, including twenty office workers and about forty workers in the field. We have our own masons, iron braiders and form finishers. Stability studies are outsourced, but we have our own calculators, draftsmen interior architects and project managers."

Can you briefly describe the Silvae project?

"Silvae" is a residential building complex with 24 apartments integrated into a park. The complex consists of three multi-story buildings resting on one common basement. This is a high-end residential project where exposed concrete is used in several places. More specifically, all walls in tree bark motif or wood grain structure, terraces in white exposed concrete and the stair cores."

(Image: Bicher Stichelhout)

What challenges did you face during the construction phase, especially when applying exposed concrete?

"The biggest challenge with exposed concrete is keeping the walls clean after the concrete is poured. After all, you want to avoid rust streaks or other contamination on the walls during the construction phase, especially if you continue construction during the winter. By applying galvanized waiting reinforcement, you avoid rust formation on walls that are exposed to stressful climatic conditions for a while. In addition, here we were dealing with terraces with horizontal reinforcement. If we were to use unprotected rebar, rust would develop and mix with the poured white concrete. Result: white concrete with spots of rust, and now that is not exactly what we imagined the customer to have (laughs)."

What are the main reasons for you to choose galvanized reinforcement?

"One of the big advantages of galvanized reinforcement is the excellent adhesion between the concrete and the reinforcement, which allows you to count with other safety factors. In fact, in almost all of our projects where we act as construction promoters, we work with hot-dip galvanized rebar for the exposed concrete. If we are a general contractor, we advise our clients to make the same choice, despite the extra cost compared to untreated reinforcing steel. We point out to the customer that if he chooses untreated reinforcement despite our advice, any rusting on the fair-faced concrete cannot be blamed on Elbeko. You can of course take the risk as a builder, but realize that you may have to paint your exposed concrete walls afterwards to "cover up" the rusting. Moreover, a painted wall is not aesthetically comparable to a beautiful, unpainted concrete wall."

Are specific preparations required on the construction site if you are working with hot-dip galvanized rebar?

"You especially need to store your rebar neatly but other than that there is no difference with untreated rebar. A little tip: make sure you work with galvanized tie wire."

Can you work with a thinner concrete cover if you use hot-dip galvanized reinforcement?

"In theory, this could be possible thanks to the optimal protection of your reinforcement, but be aware that if the concrete coverage is too small, the pattern of the reinforcing steel will mark itself on the concrete skin. Therefore, for fair-faced concrete, this makes little sense."

Let's talk about the project VILLA ED. What concrete was used here?

"VILLA ED is a residential house, consisting of two parts. On the one hand, an old renovated barn, on the other, a new construction part. in the barn, all floors are made of polished concrete. For the paths, washed-out concrete (or: brushed-out concrete) was chosen."

And where was hot-dip galvanized rebar used?

"All reinforcing steel in the polished concrete, whether it was sill profiles or ancillary reinforcement, was galvanized. Galvanized reinforcement was also used in the mezzanino, a concrete slab of about 6 by 7 m with a thickness of 18 cm. The slab incorporates both electricity, floor heating and lighting fixtures. The bottom has a wood grain texture, the top is polished. The basement of the house consists of exposed concrete walls consisting of planks of concrete of varying widths. The walls are 3.5 m high and constructed entirely with galvanized reinforcement. The result is sleek, "naked" concrete in all its natural beauty. All the waiting reinforcement in the basement is galvanized for the same reason as in the Silvae project."    

Text | Zinkinfo Benelux   Image | Elbeko