High Performance Aerogel Concrete

Abstract

Aerogel Concrete is a promising approach to fulfill the requirements for the thermal insulation of buildings. So far, Aerogel Concretes exhibit very low thermal conductivities of 0.06 ≤ λ ≤ 0.10 W/(mK) and very low corresponding compressive strength of f _cm ≤ 2.5 MPa. Thus, the suitability of Aerogel Concrete as a building material for load bearing walls was worthy of discussion. Previous efforts to achieve considerable compression strength in the range of normal strength concretes (f _cm ≈ 20 MPa) were accompanied by a significant increase of the thermal conductivity up to λ ≈ 0.55 W/(mK). By embedding silica aerogel granules in a high strength cement matrix, the Institute for Structural Concrete (ISC) at the University of Duisburg-Essen developed in cooperation with the German Aerospace Center (DLR) so called High Performance Aerogel Concrete (HPAC) with an improved correlation between compression strength and thermal conductivity. The thermal conductivities of the new material are in the range of 0.09 W/(mK) ≤ λ ≤ 0.25 W/(mK) for the High Performance Aerogel Concretes considered with compression strength between 2 MPa and 25 MPa. The dry bulk density at the same amounts of aerogel granule is less compared to previous investigations on Aerogel Concrete. The Young’s modulus related to the dry bulk density is comparable to that of Lightweight Aggregate Concrete; the flexural strength is considerable less. The mixtures are flowable, nearly self-compacting and show a short hydration process as well as an increased tendency to shrink. Subsequently, the results of the investigations on HPAC are presented in detail.