Designing with concrete

by Ofentse Sefolo
Designing with concrete

Concrete is one of the most used commodities on earth. As a base material for sustainable and resilient buildings, it offers the brute strength necessary to support storey upon storey, and thanks to its design capabilities, it can be shaped into virtually any form, with different patterns and textures.
What’s more, it has an excellent ecological profile compared to some other construction materials when one takes into account the full lifecycle of the structure. Not only does it boast exceptional durability, natural fire resistance and a high thermal mass, but it is also locally produced and recyclable.

The cement used in concrete is typically the ingredient that accounts for the most carbon dioxide emissions, but cement companies are continuously improving the manufacturing process of cement and concrete by using alternative fuels in cement kilns and reducing the clicker ratio in cement by adding cement extenders such as ground-granulated blast furnace slag (GGBS), fly-ash and limestone.

Application: Sustainable concrete design
The new city hall in Buenos Aires, Ciudad Casa de Gobierno, spans an entire city block and houses offices for the mayor and 1 500 employees. Drawing on the site’s industrial past, Foster + Partners opted for concrete as the material of choice.

The building features an in-situ exposed concrete substructure and superstructure with a high-quality, fair-faced finish throughout, with precast concrete fins to provide passive protection shading screens on the east and west facades. Inside, the concrete barrel vaulted roof is textured and exposed. The 20m tall glass curtain wall on the main facade is supported by a steel structure, which works as an independent structural system.

Every part of the building was designed in response to the local climate. Exposed concrete soffits provide thermal mass which complements displacement ventilation with free cooling to ensure comfort with low energy usage. These concrete soffits, combined with chilled beams in the floor slabs, helps to naturally regulate the temperature and keep the offices cool. Passive solar protection prevents heat gain and glare, and cooling using the external air temperature cools the building for approximately seven months of the year.

This will be the first public building in Argentina to achieve the environmental award for sustainability of LEED Silver standard.

© Nigel Young, courtesy of Foster + Partners

A progressive material
In addition to these “green” advances, other new developments are transforming concrete-based designs. New and advanced composite materials and technologies, different mixes and diverse methods and techniques are leading to innovative building design solutions.

Today’s architects have access to high-performance and ultra-high-performance concrete that offers higher strength, fibre-reinforced concrete with higher tensile and bending strength, concrete with better corrosion resistance, higher compressive strengths, higher fire resistance, quicker curing times and concrete that is lighter in weight than standard concrete.

New types of admixtures led to the development of self-healing concrete, self-compacting concrete and even self-cleaning concrete, while other additions improve thermal performance and insulation.

Aesthetically speaking, optical fibres are included to create translucent concrete and by adding pigments, concrete can be coloured. Together with methods such as tilt-up, precast and in-situ concrete and different finishing techniques, the design options are endless.

Application: The Picado technique
Menis Arquitectos used an innovative construction technique called Picado for the design of the CKK Jordanki Concert Hall in Poland. This method involves mixing concrete with other materials and breaking it afterwards, achieving a rough finish.

As a reinterpretation of the traditional use of brick, and as a tribute to the history of Toruń, red brick was crushed and melted into the concrete. The exterior was formed out of very clear, almost white concrete, besides for some parts that are “broken” to reveal shades of red as lining in the holes and leading into the interior. The two colours hint at the relation between the traditional handicraft of brick and the technology and modernity of new urban developments.

Another benefit of the Picado technique is the excellent acoustics that is achieved. This, together with the building’s dynamic ceiling, means that the space can be tuned to effectively absorb symphonic, chamber, theatre, opera and film performances – a variable acoustic allows a volume change from 8 200m3 to 6 800m3, providing a reverberation time from 1,85s to 1,20s.

© Malgorzata Replinska, courtesy CKK Jordanki

Courtesy CKK Jordanki

Concrete is still an ideal material for construction and since it is easily cleaned and simple to repair, with little or no maintenance, it can last for hundreds of years. And with ongoing research and development, the next decade is sure to see even more advancements in both the sustainability and workability of concrete.

Application: Creative renovation
Testament to the durability and reusability of concrete, an old cement factory in Spain was rehabilitated into a home for architect, Ricardo Bofill, and a workplace for his studio.

The factory started production at the beginning of the 1900s and since it wasn’t built as a whole and was half-ruined, there were many interesting elements, such as a stair that led nowhere, imposing structures of reinforced concrete supporting nothing and enormous pieces of concrete hanging mid-air.

Bofill gave the factory new life by demolishing elements and structures in order to define the space, imagining windows and doors and through greening and planting.

“In this case, the function did not create the form; instead, it has been shown that any space can be allocated whatever use the architect chooses, if he or she is sufficiently skilful,” comments Bofill.

© Luis Carbonell, courtesy of Ricardo Bofill Taller de Arquitectura

Thanks and acknowledgement are given to Foster + Partners, Menis Arquitectos, Ricardo Bofill Taller de Arquitectura and World Architecture News for the information given to write this article.

Caption Main Image:
© Nigel Young, courtesy of Foster + Partners

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