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Pore size distribution effects on the thermal conductivity of light weight autoclaved aerated concrete

100%

Kreft O. , Hausmann J. , Hubalkova J. , Aneziris C. G. , Straube B. , Schoch T.

2011

tom nr spec.

49-52

Aim of the present study was to correlate thermal conductivities of highly porous autoclaved aerated concrete (apparent density < 100 kg/m3) with appendant micro- and nano-structural properties. AAC specimens with approximate apparent densities, but different pore size distributions were fabricated through utilizing specially selected, surface active additives when preparing the slurry of raw materials, aluminum and water. The main focus of this study is on the quantitative analysis of size and morphology of both pores and solid skeleton by 3D X-ray tomography (CT) and scanning electron microscopy (SEM). Moreover, specific surface areas and pore size distributions were determined by the methods of gas adsorption and mercury porosimetry. Apparent thermal conductivities depend on the number of pores, pore size distributions and thicknesses of the separating walls of the solid skeleton. The present study provides further inside in the mechanisms of heat transfer in light weight autoclaved aerated concrete.

Porosity in autoclaved aerated concrete (AAC): A review on pore structure, types of porosity, measurement methods and effects of porosity on properties

100%

Schober G.

2011

tom nr spec.

39-43

The fraction of pore volume in AAC products covers the range from 65 to 90%. There is a set of different types of pores, e.g. large air pores are a macroscopic structural element, capillary pores and nano pores, which are connected to microstructure of the solid matrix and have specific functional effects. Different methods of pore generation and characterization of pore size distribution are summarized. Gas producing agents, foaming agents, prefabricated foam and voluminous water retarding components are compared with regard on their suitability for AAC product properties. Image analysis, mercury intrusion porosimetry, gas adsorption porosimetry and other methods are reviewed with respect of their application for AAC material. Influence of pore size, pore shape, proportion of different pore types on related properties is presented and discussed. Homogeneity of material, isotropy of properties and range of property values with respect to porosity influences are regarded.

Rozmieszczenie porów powietrznych w betonie z dodatkiem fluidalnego popiołu lotnego

100%

Glinicki M. A. , Zieliński M.

2007

tom R. 12/74, nr 3

133-138

Zbadano rozmieszczenie porów powietrznych w betonie z dodatkiem fluidalnego popiołu lotnego. Dodatek ten zastępował cement aż do 40%. Doświadczenia wykazały konieczność proporcjonalnego zwiększania domieszki napowietrzającej z rosnącym dodatkiem tego popiołu. Oceniono rozmieszczenie porów powietrznych w betonie za pomocą metody numerycznej analizy obrazu polerowanych zgładów. Przeprowadzono analizę wpływu dodatku fluidalnego popiołu lotnego na odległość między porami i ich powierzchnię właściwą.

The microstructure of air voids in air-entrained concrete, with addition of fly ash from fluidized bed coal combustion was investigated. The additive was used as partial replacement of cement up to 40%. Tests have revealed the necessity of proportional higher addition of air-entraining agent to concrete to assure the required air content with increasing content of this kind of fly ash. The distribution of air voids in concrete was evaluated using a digital method of image analysis on polished sections. The influence of addition of fly ash from fluidized bed coal combustion on spacing factor and specific surface of voids is discussed.