Characterisation and modelling of dewatering in lime mortar systems.

Mortars, together with plasters and renders, are unique amongst construction materials in two respects: they are applied in the freshly-mixed wet state as thin layers to absorbent substrates, and they are dewatered to varying degrees by these substrates prior to the transformation from soft to rigid solid. In this project the dewatering characteristics of each substrate studied will be measured using a new technique to determine a characterising capillary suction force for that substrate. This force defines the pressure at which fresh mixes are dewatered by the substrate. Controlled dewatering of fresh mixes at this pressure will then be achieved in the laboratory using a pressure cell technique to produce specimens which will be studied in detail as they harden. An extensive range of experimental studies using synchrotron diffraction, electrical impedance spectroscopy and electron microscopy and spectroscopy will give new insights into the fundamental changes in structure and composition of these mixes during hardening. The work will focus on mortar mixes based on lime. This experimental work will be coupled with further developments of the theoretical modelling of dewatering based on unsaturated flow theory The findings of this work have generic application, being relevant to the change in properties of other soft solids in chemical and oilfield engineering, food technology and paper science.