White Concrete Acoustics

Excellent acoustics through White elements

White Concrete Acoustics

Concrete acoustics
The outstanding acoustics of the Mariinsky Theatre are produced by special exposed concrete elements made from white cement.

After ten years of construction work, now the extension of the St. Petersburg’s Mariinsky Theatre was opened. From the outside the design of the new building is relatively simple, but the inside convinces with an outstanding acoustic. This was attained by the company B & T Bau & Technologie GmbH using concrete elements for which CRH white cement was an essential constituent.

Originally built in 1860, the Mariinsky Theatre is one of the most renowned operas and ballet theatres in the world. Situated onSt. Petersburg's theatre square, it has been under the control of artistic director Waleri Gergijew since 1996. After campaigning to have an extension added to the building, Mariinsky Theatre 2 was opened in the spring of 2013.

Design phases
The architect Dominique Perrault was originally contracted with conceptualisation of the new building. The Frenchman envisaged a yellow, capsule shaped structure made of steel and glass. Unfortunately, this plan proved not to be feasible due to the weather and ground conditions inherent inSt. Petersburg. Although it was already clear as early as 2008 that an alternative solution would have to be found, the responsible parties authorised commencement of work on the French design. The following year, architectural firm Diamond & Schmitt fromTorontotriumphed in a second competition to devise erection of a realisable theatre on top of the existing foundation walls. These plans were ultimately brought to fruition.

Architecture
Following an overall construction period of 10 years, the 500 million Euro structure was opened to the public. Measuring approximately 80,000 square meters of floor space and comprising seven upper-level and three lower-level floors, the façade is rather basic and lends a striking contrast to the splendid ornamentation of adjacent buildings. The interior is styled on the horseshoe shape of Italian theatres and provides room for up to 2,000 guests over three tiers. Visitors will be in awe of the 4000 m² of Iranian onyx with background lighting, Brazilian marble and sparkling Swarovski chandeliers, albeit very briefly before they pale quickly into comparison with the state-of-the-art stage technology and superb acoustics.

Stage technology and acoustics
All planning in this regard was assigned to the company Müller-BBM ofMunich, the execution of which was heavily dependent upon structural elements from B & T Bau & Technologie GmbH (B & T), Raubling. The company specialises in the production of unusual precast concrete sections and manufactures elements which are far too complex for other companies working in the same field. For this reason, renowned architectural icons such as Sir Norman Foster or Zaha Hadid are counted amongst the many customers of the globally operational concrete specialists.

CEton – Utilising new materials
B & T owner Kruno Stephan Thaleck developed a cement-based building material for Zaha Hadid in 2012 which allowed the production of elements featuring a thickness of only 40 mm. Weighing only 30 kg/m², this material can be applied to adopt practically any 3-dimensional form. To ensure protection of his development, the businessman had the building material patented under the name CEton. He now incorporated a slightly modified version in Mariinsky Theatre 2. The entire ceilings of all balconies and the main ceiling of the theatre were manufactured using this innovative building material before being transported toSt. Petersburg. In addition, Kruno Stephan Thaleck also developed special resonating bodies, at least one unit of which was integrated into each ceiling element to attain the high acoustic requirements. The individual elements are up to 10 m² in size and some feature double-curved surfaces. Before commencing actual production, however, B & T were required to work in close collaboration with employees of the Müller-BBM company. Around 15 samples were produced in advance and tested intensively for their acoustic and architectural properties.

White cement – for effective colouring
A radiant white colour was required for all ceiling elements in accordance with overall design of the theatre. CRH white cement was used by B & T to guarantee this specification. Kruno Stephan Thaleck explains: „White cement from CRH was incorporated into the recipe for CEton. This allowed us to produce snow-white surfaces, while at the same time providing us with the advantage of attaining a desired shade every time with the addition of pigments.“ Unquestionably, the white cement from CRH does indeed offer numerous advantages over its grey counterpart: Should colour be added for example, it is possible to produce considerably more brilliant colours than would be possible with grey cement. Sold by the company under the name CRHWhite, the cement also maintains high standards with regard to consistency. Precisely the same grade of consistency can be attained as that produced with grey cement. Moreover, no differences are evident with the utilisation of concrete additives etc. We can therefore conclude that incredibly quick fabrication of the ceiling elements was due to the excellent quality of the cement and the outstanding composition of CEton. Just 12 hours after casting the concrete, the prefabricated parts were ready to be packed and loaded.

Company undertaking the work
B & T Bau & Technologie GmbH
Am Holzplatz 12-14
D-83064 Raubling
www.clarolon.de

The Mariinsky Theatre owes its excellent acoustics to the special Ceton-faced concrete elements of white cement.