First Utilization of High-Strength Concrete in Germany

The production of high-strength concrete (HSC) up to a concrete class of B 125 as a ready-mixture does not represent a real problem nowadays. This has been shown clearly by the first utilization of a HSC of B 85 in Germany on a 186 m high-rise building in Frankfurt/Main completed in 1992. The concrete mixture used reached a strength mean value of 112 N/mm² on the job-site. To safely reach such strength classes, special concrete admixtures as well as a comprehensive quality assurance programme are needed. HSC presents considerably distinct characteristics compared with normal-strength concrete. Certainly, these new concrete classes are beyond the scope of German and many other international standards and design methodologies, including many design equations based on test results from specimens with concrete strengths of less than 40 N/mm². Particularly in the design stage, the increased brittleness of HSC should be kept in mind. In the following, some results concerning the concrete mixtures and the bases for design of HSC columns will be given.