The newly constructed Maillon Theatre in Strasbourg, France, is set to open its doors in autumn this year. Concrete admixtures from Master Builders Solutions® have contributed to the look of the new building, as well as its durability, whilst also ensuring a straightforward construction process in view of a challenging formwork configuration.
“Using MasterPolyheed 520 and MasterGlenium SKY 841 plasticisers provided all of the 1700 m3 of concrete used with workability and flowability,” said Dominique Cuadras, who is responsible at BASF for Master Builders Solutions concrete admixtures in eastern France. “This combination served to significantly reduce the water content of the concrete mix, ensured fluid and uniform consistency, and ideal viscosity properties. The emulsion effect could be minimised as well, preventing blowholes and undesired streaks.”
Challenging formwork configuration
The formwork-based in-situ placement of the concrete for the large façade elements presented one of the major challenges of the project. Set up vertically, one on top of the other, the formwork segments reach a height of 14.5 m, at a thickness of only 10 to 40 cm.
Each façade element was cast using 45 to 65 m3 of black concrete. “While filling the formwork with concrete, speed was essential,” said Alain Albizati, Managing Director of Albizati, the project contractor. “The concrete was open for only two hours, and any delays in the pouring schedule involved the risk of creating excess pressure inside the framework, and, as a worst-case scenario, having to restart the entire concreting process. Thus, excellent viscosity was a vital prerequisite for concreting.”
A customised placing technique was employed to obtain a particularly uniform distribution of the concrete: the concrete was placed using a sacrificial tremie pipe with hatches along its entire length that opened one after the other, triggered by the freshly poured concrete as it rises within the framework. This technique ensures uniform concrete placement without any fouling of the formwork.
Black as a design element
Designed as a ‘black box’, the building derives its characteristic aesthetics from the deep black colour, employed by French-Italian architects, Local Architecture Network (LAN), as a crucial design element. This is why the MasterColor 100 Noir Intense additive – characterised, in contrast to conventional black concrete pigments, by its intensity and brilliance – was selected. The effect was increased by using MasterPel 795, which not only further enhances colour brilliance but also prevents lime efflorescence.
“MasterPel prevents the decomposition of calcium carbonate on the surface of concrete elements,” said Michael Nowak, BASF Engineer. “This, in turn, prevents water from penetrating the concrete surface, and so increases weather and freeze/thaw resistance.”
In order to obtain a protective effect, the Master Builders Solutions experts also used the MasterPel 300 admixture.
“MasterPel 300 makes surfaces water and oil repellent and prevents efflorescence,” Nowak noted. The company has noted that it also intensifies colours, facilitating the deep black appearance of the façade.
“Black provides objects with an abstract quality,” said Francisco Martinez, architect with LAN and responsible for onsite execution. “Using the products from Master Builders Solutions enabled us to obtain the exact colour we intended and a brilliance that is compelling and will remain so for a long time.”
Situated in Strasbourg’s Wacken district and at a short distance from the European Parliament, the new theatre building provides two auditoriums for a total audience of 950 and an overall floor space of 6700 m2. Budgeted at €27.5 million, construction began in October 2016.