Fresh properties of cement-based thermal renders with fly ash, air lime and lightweight aggregates

Abstract

The environmental impact reduction has a growing prominence in building constructions. One of the solutions to that is external wall coating mortars with improved thermal performance, which can be produced with incorporation of lightweight aggregates. To obtain a mortar with the demanded hardened characteristics (physical and mechanical), their fresh properties must be acceptable. This study is focused on the fresh state properties of mortars with improved thermal performance. The mixes were produced with incorporation of different lightweight aggregates (expanded clay, expanded cork granules), a main binder (cement), supplementary materials as partial replacement of cement (fly ash, air lime) and admixtures (air entraining agent, water retaining agent). In this paper, the selected mortars with acceptable workability were tested for fresh density, flow, air content, and water retention. Lastly, the relationship between the fresh and hardened properties (obtained from a previous study) was assessed to highlight the importance of fresh properties. In conclusion, the mortars’ fresh behaviour was mainly influenced by the incorporation of different lightweight aggregates and admixtures. In addition, an optimization was carried out to select the most adequate thermal mortars for the external wall coatings from two perspectives, namely the overall performance (fresh properties, compressive strength, capillary water absorption, thermal conductivity) and the individual thermal performance.