The thermal parameters of mortars based on different cement type and W/C ratios

Abstract

This study examines the thermal parameters of mortars based on different cement type and water-cement W/C ratios. The presented relationships are important from the point of view of thermal insulation of the entire building component, of which the mortar is a part. The thermal properties of the mortar, and in particular its dependence on the degree of moisture, is important information from the point of view of hygrothermal simulations of building components. The moisture effect on the thermal properties was tested using nine mortar types. The study consisted of producing nine types of mortar on the basis of three cements (CEM I 42.5R, CEM II A-S 52.5N, CEM III A 42.5N). For each cement type, three variants of specimens were prepared which differed according to their water/cement ratio (0.50, 0.55 and 0.60). The main research of thermal parameters was carried out using a non-stationary method based on the analysis of changing heat flux readings. The thermal conductivity, volume-specific heat and thermal diffusivity values were analyzed. The tests performed allowed for determination of the density of specimens, water absorbability and thermal parameters in three water saturation states: dry, natural and wet. Additional microstructural tests were performed using mercury intrusion porosimetry. The obtained parameters were used to determine the relationship between the measured properties. An adverse effect of dampness on the thermal insulation of the studied materials was confirmed. In extreme cases, the increase in thermal conductivity due to material high moisture was 93%. The cement used affects the relationship between the total specific surface area and the W/C ratio. As expected, the total porosity of specimens was higher for mortars with higher W/C ratios. A strong correlation has been demonstrated between the total surface area and thermal conductivity. The opposite results were obtained when assessing the relationship between the total specific surface area and water absorbability. In case of specimens CEM II A-S 52.5N, the relation was the proportional, and in specimens CEM III A 42.5N, the relationship was inversely proportional to the W/C ratio.