TY - CONF A1 - Klobes, Peter A1 - Rübner, Katrin A1 - Prinz, Carsten A1 - Hempel, S. T1 - Investigation on the microstructure of ultra high performance concrete T2 - 8th International Symposium on the characterisation of Porous Solids N2 - Ultra-high performance concrete (UHPC) is characterised by compressive strengths above 150 MPa and an outstanding durability. These properties are achieved by optimisation of the mixture composition, the mixing procedure as well as the curing conditions of the concrete. Heat curing as well as the use of vacuum mixers may contribute to the high strength. The very high brittleness of UHPC can be compensated by the addition of steel or polymer fibres. UHPC is produced using a very low water/cement ratio of 0.25 or smaller in combination with adding of polycarboxylate ether based superplasticisers. Furthermore, finest cements with contents of 500 kg/m³, defined selections of coarse and fine aggregates with a maximum grain size between 0.5 and 8 mm and fine pozzolanic (silica fume, fly ash) and inert additives (quartz filler) are used. In doing so, the aim is to obtain a very high packing density of the cement paste matrix and the aggregate/paste interface while a very homogeneous microstructure with a high calcium silicate hydrate (CSH) portion is formed. In the case of optimal mixing and curing conditions, UHPC contains almost no pores and microcracks. Therefore, studies of porosity and pore structure are very important to characterise UHPC materials in connection with the mixture optimisation. Here, the experimental results for UHPC are presented in comparison with those of high-strength concrete (100 MPa) and normal-strength concrete (35 MPa), respectively. T2 - 8th International Symposium on the characterisation of Porous Solids CY - Edinburgh, Scotland DA - 11.06.2008 PY - 2008 AN - OPUS4-16396 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -