, Volume 46, Issue 9, pp 1537-1546
Date: 11 Dec 2012

Analytical and experimental study on thermal conductivity of hardened cement pastes

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Abstract

Thermal conductivity of hardened cement pastes (hcps) in a wide range of water–cement ratio (w/c) is quantitatively investigated using a transient plane source measurement technique. Alkyl alkoxysilane and rapeseed oil were also added to determine the effect of internal hydrophobation on thermal conductivity of solid structure of hcps. The measurements were performed after drying at 50 and 105 °C as well as water submersion. A nonlinear relation was observed between thermal conductivity and w/c which is in alignment with Powers’ model. Samples dried at 50 °C still contained some moisture which increased thermal conductivity up to 11 % compared to samples dried at 105 °C. Furthermore, hydrophobic agents reduced thermal conductivity of dried samples up to 9 % which indicates the reduction in thermal conductivity of solid structure and is in line with observations by scanning electron microscope. A three phase model which can predict thermal conductivity of plain and hydrophobed hcps at different moisture states is presented by exploiting composite models and Hashin–Shtrikman bounds.