Development of a New Multifunctional Structural Material: High Performance Aerogel Concrete

Abstract

The Institute for Structural Concrete (ISC) at the University of Duisburg-Essen developed in cooperation with the Institute of Materials Research at the German Aerospace Center (DLR) a new multifunctional structural material: High Performance Aerogel Concrete (HPAC). Chief ingredient of HPAC is silica aerogel granule which is embedded in a high strength cement matrix. Aerogel Concretes described so far in the literature exhibit very low thermal conductivities of 0.06    0.10 W/(mK) and very low corresponding compressive strength of fcm  2.5 MPa. Thus far the applicability of Aerogel Concrete as a building material for load bearing walls had to be discussed. Previous attempts to achieve the compression strength of normal strength concretes (fcm  20 MPa) involved a significant rise of the thermal conductivity up to   0.55 W/(mK), which counteracts the benefits of Aerogel Concrete in thermal insulation. The mixtures optimized by the ISC achieved thermal conductivities of   0.25 W/(mK) at a compressive strength comparable to Normal Strength Concrete (NSC). Compared to previous investigations, the thermal conductivities were considerable less over the full spectrum of investigated compressive strength in the range 2 MPa  fcm  25 MPa. Beyond this improved correlation between compression strength and thermal conductivity, HPAC shows some remarkable properties that make it a real multifunctional structural material: By means of pull-out tests the general suitability of HPAC for reinforced construction elements was proved. Shear tests and adhesive tensile tests showed that it is possible to fabricate graded construction members made of HPAC. The building physical properties are also very promising: The measured sound absorption is higher compared to normal strength concrete. HPAC is water-repellent, open to diffusion and fireproof (melting point approx. 2000°C).