Hygrothermal behaviour and relative humidity buffering of unfired and hydrated lime-stabilised clay composites in a Mediterranean climate

Three different basic mixtures were prepared, by mechanical compaction, with different types of clays: quarry fine, kaolinite, and bentonite. Two groups of mixtures were studied, the first group without lime and the second with the addition of 5% hydrated lime. A comparison between the measured hygrothermal performances of the mixtures and their microstructural composition was performed. Microstructural morphology and chemical composition was characterised using SEM with EDS, mineralogy using XRD, and porosity using gravimetrics/He pycnometry and N2 physisorption with BET and BJH analysis. Hygrothermal functional properties were characterised as moisture-dependant thermal conductivity, moisture-dependent heat capacity, vapour sorption isotherms, and water vapour permeability. The hygrothermal behaviour of a TESTROOM in a Mediterranean climate was simulated using WUFI Plus v2.1. The model simulated was repeated for three different internal surface types; an earth-bentonite panel, unpainted gypsum plaster, and an acrylic stucco plaster. Results demonstrated that the earth-bentonite gave the best hygric performance in terms of humidity buffering and, when used in conjunction with an HVAC system, achieved a significant (30%) operational energy saving in terms of humidification/dehumidification.