Effective thermal conductivity of clayey aerated concrete in the dry state: experimental results and modelling

The aim of this study was to determine the effective thermal conductivity o f a new insulating building material, called clayey aerated concrete (CAC), when used in a dry state. A series of six mixtures having different porosi ties obtained by adding aluminium powder to the clay-cement matrix was used in the investigation. The measurements of thermal conductivity have been p erformed inside a closely controlled climatic cell at ambient temperature ( 20 +/- 1 degrees C) using a 'line source' method. The experimental results reveal that enhanced thermal performances can thus be obtained by the devel opment of local materials, and their use in building insulation reveals ver y interesting properties as compared to other building materials. The study has been extended to the research of theoretical models capable of predict ing the effective thermal conductivity of dry CAC considered as a two-phase system. Three models based on a geometric mean approach (Asaad model, Veer endra and Chaudhary model) and a effective continuous medium approach (Pand e and Chaudhary model) were used. In order to predict effective thermal con ductivity of elaborated material using such models, a correction term has b een empirically determined and introduced in these models, taking into acco unt the effect of a higher ratio of the thermal conductivity (lambda(s)/lam bda(f)). A very good agreement has been observed between the analytical and experimental results, thereby confirming the model's ability to predict th e effective thermal conductivity of dry CAC.