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precast concrete facade panels

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characteristics and propertiesArchitectural precast concrete became popular from the 1960s onwards: precast concrete was already used for façades before because of its formal and aesthetic possibilities, but the remarkable evolution of the precast industry in Belgium from the end of the 1950s onwards, both qualitative as quantitative, gave a strong boost to the application of architectural precast concrete in the 1960s and 1970s. In architectural precast concrete, the structural, economical and functional advantages of concrete are combined in one element, which can be designed in the most diverse ways. The most common types of panels are frames, solid panels and parapets. The design is not limited to fl at surfaces: curved forms are possible thanks to moulds in ‘plastic’ materials, while surface treatments can create a textured surface (relief or imprints, polished, sandblasted, retarded concrete, etc.). Because of the order and rationality that is implied by prefabrication, the dimensions of the prefabricated elements are usually multiples of 30 cm, e.g. 1,20 m, 1,50 m, 1,80 m or 2,40 m. The module of 30 cm is mainly used for widths; for heights, usually the elements are dimensioned from fl oor to fl oor. If the concrete façade elements are designed like frames, the windows can be incorporated in the prefabrication factory. In the case


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of fi xed windows, the concrete can even act as window frame and the glazing bead is simply screwed into the concrete.

Given the structural capacities of reinforced concrete, the precast concrete façade elements often have a loadbearing function. The compression strength for façade elements had to be over 120 kg/cm² (150 kg/cm² for smooth concrete), according to the directions published by the Belgian federation of precast concrete companies in 1975. The reinforcement bars had a diameter of 16 mm maximum to avoid cracks. Still in 1975, the concrete cover had to be only 2 or 3 cm, depending on the orientation of the surface. As for tension forces, cracks needed to be taken into account during the design process as an important issue in façades exposed to wind and rain. Cracks can be caused for example by unequal deformation of the prefabricated façade elements and the beams on which they rest, or by (a difference in) thermal dilatation.

The joints and connections with other façade or structural elements were constructed in many different ways. For example, protruding reinforcement bars of the prefabricated façade elements were connected to the protruding bars of other elements, after which the joint was fi lled with in situ concrete. Or the protruding bars were connected to the reinforcement of the skeleton structure, cast in situ, so that the façade element acted as a permanent mould for the columns on one side. Non-loadbearing façade elements were also hung on adjustable anchors in stainless steel. Parapets are supported by concrete consoles and fi xed with bolts. The joints between different elements could be ‘open’ (underlying) or ‘closed (close to the surface), which were in both cases fi lled with mortar or a (synthetic) sealer. In 1973, in a technical work-book on architectural precast concrete, the Belgian federation of precast concrete companies advised to use Thiokol for the vertical connection between façade elements to create a watertight joint. Thiokol is a special synthetic rubber, based on dichloroethane and sodium polysulfi de, used as an elastic sealers in expansion joints and glass. The joints were typically between 6 and 18 mm wide. For the horizontal joints, which not only have to be watertight but also have to transmit the loads, a 5 cm joint in micro-concrete with an adjustable bolt is used.

From the 1960s onwards, and especially after the fi rst oil crisis, concrete façades were more and more designed as sandwich elements. The catalogue of the model home exposition/building yard ‘Villagexpo’ in Moeskroen in 1970-1971 showed 2 houses with a sandwich façade: the inner and outer façade panel were both in

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concrete, with insulation between them. In one of these (by the company Rhodius-Deville from Namur), no special surface treatment was executed, while the other (by the building company Maes from Ghent) foresaw a relief texture or an inlay of white stones. In 1972-1973, the Villagexpo ‘Le Beau Champ’ in Limal also showed a few individual houses or bungalows with sandwich elements. The involved building companies (Van Den Bogerd-Elst, Declerck and Van De Kerckhove’s Prefa) all chose for concrete sandwich panels with exposed fl int aggregate.

A very specifi c, popular type of precast concrete façade elements, albeit somewhat smaller than most ‘panels’, are claustras: small, open precast elements with various, geometric patterns can be used repetitively to create ‘open-work’ screens or as a decorative ‘accent’ in masonry.

brands & productsDuring the 1960s and 1970s, various concrete companies in Belgium produced façade panels in architectural concrete. In 1975, the catalogue of the Belgian federation of precast concrete companies listed thirty manufacturers of façade elements, more specifi c frames, parapets and fl at panels in architectural concrete. When we add the manufacturers of claustras, listed in the permanent catalogue of 1978, we count 35 manufacturers in total.

Some of the more signifi cant market players were CBR-Ergon, Seghers Prefalith Beton, Marbra-Lys plc, Eurobeton plc and Vandewalle. All of these factories specialized in diversity, meaning that they all tried to offer the broadest possible range of products, instead of focusing on one particular style or element. The infi nity of choices was something that the industry explicitly launched out about. The 1975 catalogue shows that most companies produced different types of panels, both loadbearing and non-loadbearing, both existing of one single wall element or a sandwich element, with or without insulation in between. The four main surface options were smooth, washed, acid-scoured or sandblasted concrete. Except for the structural type and surface treatment, also the general form, the connections and details, and the chemical composition could vary strongly within the assortment of one manufacturer. Fillers and additives like plasticizers, bond accelerators or bond retardants, bubble formers, colour pigments, glass fi bres, etc. allow for the manipulation of strength, thermal and acoustic isolation, weight, colour and texture, and even the transparency of the material.

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Agraf x x x x

Anseeuw x

Antw. Machienst. x

Bevisol x x x

Beton de Callenelle x x x

Carolith x x

Cavan x x x

CBR x x x

Chaux de Contern x x x

Dauchot x x

De Beuckelaer x

De Clercq x

Eurobeton x x x

Fixolite x x x

Gelderbeton x x x

Goudezeune x x

Beton Jo x x x

Lithobeton x x x

Marbralys x x x x

De Nethe x x x

Proost x

Rodal x

SVK x x x x

Schmidt x x

Seghers Beton x x x

Sintra x x x

Sobeco x

Structo x

Torfs x x

Van Cauwenberghe x

Vandewalle x x x

Van Doninck x

Van Thuyne x x

Vuylsteke x x

Westvlaamsche BW x x

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By (small) variations in materials, forms, proportions and techniques, innumerable types of concrete panels exist. Therefore, we will not discuss products but only companies. Next to the most important Belgian precast companies, we also present the Dutch company Schokbeton which was also active in Belgium.

CBR-Ergon Almost immediately after its establishment in Lier in 1963, CBR-Ergon started a research and production line for façades in ornamental and architectural concrete. Ergon was a daughtercompany of the Cimenteries et Briqueteries Réunies CBR, producing precast concrete elements. Although Ergon mainly focused on standardized products such as beams, columns and hollow core slabs, they also had a department for façade elements in architectural concrete. The research focused on the composition of the mixture, the compaction of the wet concrete, the formwork and the texture and fi nish of the elements. With some remarkable offi ces in architectural concrete designed in collaboration with architect Constantin Brodzki, Ergon became one of the major players in this fi eld. The ‘CBR-style’ for offi ces in architectural concrete was copied by other fi rms, but for architectural concrete panels in residential buildings CBR-Ergon had no specifi c style or typology.

Seghers Prefalith BetonSeghers Prefalith Beton in Aalter started with the production of architectural concrete in 1956. The acquisition of new sites in 1967-1968 in Aalter coincided with a considerable expansion, including new production units for architectural concrete and fi bre reinforced concrete with extensive scientifi c and industrial equipment. The production line for architectural concrete was organized according to a 24 hour-production cycle. The formwork was fi lled by a fully automated mixing plant. After the elements were compacted on heavy vibration tables, they were transported into a climate tunnel for curing. At the end of the tunnel, the elements were demoulded and underwent a fi nal surface treatment. Seghers Prefalith Beton realized offi ce buildings, residential buildings and public buildings such as schools and municipal administrative centres. In 1985, the company was taken over by Loveld plc.

Marbra-Lys plcMarbra-Lys was originally a supplier for building materials, established in Kortrijk from 1913. During the 1950s, the company moved to Harelbeke and the emphasis

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shifted to the industrial production of tiles, claustras and stairs in marble mosaic, artifi cial stone and artifi cial marble ‘marbralyth’. From the 1960s onwards, façade elements were also produced in artifi cial concrete, especially for applications in offi ce buildings and apartment buildings. Architectural concrete was precast in a 150 m long production hall, which included also set-up for vibrating and steaming the concrete. At the end of the 1990s, Decomo took over Marbra-Lys’ department for architectural concrete.

Eurobeton plcEstablished in 1964 in Massenhoven, Eurobeton plc grew into an important manufacturer of architectural precast concrete. The range mainly consisted of frame-like elements, parapets and fl at panels, for offi ces, public buildings, etc. Eurobeton used both wood and metal formworks fi xed to vibration tables, and portable formworks in plastic and metal.

Kunststeenfabriek VandewalleThe artifi cial stone company Kunststeenfabriek Vandewalle was established in 1960 in Roeselare, by the same family that had already founded a tile factory in 1920. Vandewalle developed from relatively small decorative elements in artifi cial stone to load-bearing, high-quality and fully fi nished elements reaching from fl oor to fl oor.

SchokbetonSchokbeton was invented in the Netherlands in 1931 as a new way to prefabricate concrete: the formwork was fi xed on a special vibration table and ‘shocked’ intensively while being fi lled with concrete. This setup ensured an extremely rapid and effective compaction: the excess water and air was literally shocked out, with an exceptionally durable, stiff and slender (and therefore economical) element as a result. The production process guaranteed a qualitative execution and fl awless surface. If desired, the elements could receive an extra surface treatment in the factory, e.g. sandblasting or acid-scouring. An important disadvantage however was the need for very heavy machinery, therefore leaving the technique out of reach of small contractors, unless they ordered the elements from the Schokbeton factory in Zwijndrecht (NL). From the 1950s, Schokbeton was also used in other European countries (Belgium, France, Germany, Switzerland, Austria, Spain, Italy, Finland, etc.), as well as in Africa, Asia and America, where well-known architects like

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Marcel Breuer, Frank Lloyd Wright, Philip Johnson, Minoru Yamasaki, Gordon Bunshaft and Edward Durell Stone worked with Schokbeton during the 1960s. In Belgium, Schokbeton was used from the early 1950s onwards, for example in social housing projects in Brussels (Les villas de Ganshoren, arch. Gaston Brunfaut and Albert Van den Bossche), Antwerp (Jan de Voslei, arch. Jos Smolderen; Luchtbal, arch. Hugo Van Kuyck) and Liège (Angleur and Plaine de Droixhe, arch. Groupe EGAU). In these and other applications, Schokbeton was used especially for its economical and durability qualities.

applications in house building in brusselsPrecast concrete façade panels are mostly used in apartment buildings; examples of applications in individual houses are rare.

- Les villas de Ganshoren, precast concrete: Schokbeton

- Apartment building Bellini, Brussels, arch. RJ Brunswick, O. Wathelet, contractor: sprl Vincent, precast concrete: Seghers Prefalith

- Apartment building Astronomie, Brussels; arch Goffi aux, contractor: L’Ecluse, precast concrete: Seghers Prefalith

- Résidence Pacifi c, Brussels, arch Barbier, contractor Socol and CEI, precast concrete: Blocbéton

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bibliography

Schokbeton, Habiter/Wonen, 1962, no. 18-19, pp. 165-170.

characteristics and properties


SchokbetonHabiter/Wonen1962, no. 18-19, pp. 165-170.

brands and products


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SCHOKBETON

Betonconstructies, betonproducten, bimsbetonBouwen en Wonen1954, vol. 1, no. 3.

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SCHOKBETON

Schockrete gevel-elementenBouwen en Wonen1955, vol. 2, no. 10.

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SCHOKBETON

SchokbetonLa Maison1960, vol. 16, no. 4, p. LXXXIX.

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PREFALITH

Éléments préfabriqués en bétonLa Maison1960, vol. 16, no. 10, p. CCXXV.

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SCHOKBETON

Éléments préfabriqués en béton noble et décoratifLa Maison1967, vol. 23, no. 7-8, p. CLXXVII.

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SCHOKBETON

Éléments préfabriqués en béton nobleLa Maison1967, vol. 23, no. 9, p. CCXIII.

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SCHOKBETON

La Maison1968, vol. 24, no. 7-8.

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SCHOKBETON

Béton décoratif, éléments préfabriqués en béton arméLa Maison1968, vol. 24, no. 10.

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SCHOKBETON

Éléments préfabriqués en béton noble et décoratifLa Maison1967, vol. 23, no. 7-8, p. CLXXVII.

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