Economic Mix Design Ultra High-Strength Concrete


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Title: Economic Mix Design Ultra High-Strength Concrete

Author(s): K. Holschemacher and D. Weiße

Publication: Special Publication

Volume: 228


Appears on pages(s): 1133-1144

Keywords: compressive strength; crushed aggregates; fly ash; mix design; silica fume; tensile strength; ultra high-strength concrete (UHSC); workability

Date: 6/1/2005

Ultra high strength concrete (UHSC) is undoubtedly an engineered high-tech material, which can be seen as the latest step in the concrete technology development. It is characterized by extraordinary mechanical properties, e.g. high compressive and tensile strength as well as large elastic modulus. For the development of ultra high strength concrete the compressive strength was the relevant factor, therefore suitable mixes normally contain large quantities of cement and silica fume (³ 700 kg/m³), special aggregates and chemical admixtures. Consequently the material costs of this concrete type are very high. The aim of this investigation was to develop different UHSC-mixes in order to minimize the material costs. Furthermore, normal mixing and compacting intervals were used, so that the concrete can be easily handled on site, including pumpability. This paper outlines an experimental program and its results for the development of economic mixes for UHSC. Altogether 69 different mixes were tested on the fresh and hardened properties. Especially the cement type has a significant influence on the workability and the ultimate strength. It could also be shown that a strength of 150 N/mm² can be reached with a maximum cement content of 500 kg/m³.