Description of thermal and humidity parameters of mortars with the addition of cenospheres

Reliable hygrothermal data are essential for modelling heat and moisture transport in building envelopes. This study investigates six cement mortars in which quartz sand is progressively replaced by cenospheres from 0% (REF) to 100% by volume (C100). The composites were characterized in terms of bulk density, water absorption, sorption–desorption behaviour and thermal conductivity in dry and water-saturated states. The dry density decreased from 2.07 g/cm 3 (REF) to 0.85 g/cm 3 (C100), while water absorption increased from 8.1% to 23.7% by mass. The thermal conductivity in the dry state dropped from 1.77 W/mK to 0.25 W/mK, whereas water saturation increased λ in all mixtures, although this effect was less pronounced for high-cenosphere mortars. Dynamic vapour sorption tests (0–97% RH) showed that maximum hygroscopic moisture content increased from about 3% for REF to nearly 10% for C100, and that mortars with cenospheres released sorptive moisture significantly faster; for example, C100 lost 4.07% of its mass after 1 h of desorption and reached equilibrium much earlier than the reference mortar. Empirical relationships were derived between water absorption and density, and between thermal conductivity and both density and moisture content, providing practical input data for hygrothermal simulations of cement composites modified with cenospheres. • Oswin model accurately predicts sorption isotherms for cenosphere-cement composites • Mathematical coupling of sorption and thermal models predicts material performance • Cenospheres reduce mortar density to 0.85 g/cm 3 and thermal conductivity to 0.25 W/mK • Cenosphere composites achieve moisture equilibrium ∼3× faster than reference mortars • Desorption kinetics strongly correlate with cenosphere content and pore structure