Rheological and thermal properties of aerated sprayed mortar

- Shootability of aerated cement paste was studied.
- Additions were used to study influence in rheological properties.
- Sepiolite and metakaolin additions increase yield stress and water retention.
- Thermal conductivity of hardened pastes was tested.
- Additions used provide the largest expansion speed increase.

This paper studies the rheological properties in aerated cement pastes in order to develop an aerated sprayed mortar with low thermal conductivity. For this purpose, different mixtures of cement with additions of metakaolin (MK) and sepiolite (SP) were tested. In addition, influence of yield stress on build-up thickness, as well as expansion speed and pore network were studied using cement pastes aerated with aluminum powder. At the same time, the volume increase during expansion, water retention and yield stress of the fresh foamed cement pastes were studied to characterize the fresh mortar. Results obtained show that the incorporation of siliceous fly ashes (SFA) in ordinary Portland cement together with additions of MK or/and SP provided the largest expansion speed increase and the lowest density of the aerated mortar. Pastes with greater yield stress show higher thermal conductivity but are better to be pneumatically gunited due to its bigger build up thickness. The most suitable paste from all them was selected, sprayed and aerated over ceramic bricks, checking the results on site. Results obtained by means of these tests confirm that is possible to spray an aerated mortar over vertical surfaces. In addition, this mortar has acceptable thermal insulation properties to be used in chambers of building façades and for external wall thermal insulation systems (EWIS).