Capillary absorption of water and n-decane by autoclaved aerated concrete

An autoclaved aerated concrete was one of three construction materials used in the round-robin study of hygral properties carried out in the European Commission funded Heat, Air and Moisture Standards Development [HAMSTAD] project (Roels S et al., Journal of Thermal Envelope and Building Science 2004 27 307–325). The material has fine micron-scale matrix porosity generated by the packing of thin tobermorite 11Å plates; and coarse mm-scale aeration pores arising from the foaming of the wet mix. We treat the material as having a strongly bimodal pore size distribution. Capillary absorption does not obey simple t1/2 kinetics. We report here the results of liquid uptake tests using both water and n-decane to investigate the cause of the imbibition behaviour. The transport properties are modelled in a Sharp Front analysis as a parallel combination of absorption into the coarse aeration pores and into the fine matrix pores. The aeration pores have weak capillary suction and absorption into these pores reaches capillary rise equilibrium during the test. The Sharp Front model is applied here for the first time separately to subsets of the total porosity. The matrix sorptivity of the autoclaved aerated concrete studied (density 450 kg m− 3, porosity 0.82) is about 0.23 mm min− 1/2.