Preventive Conservation is argued to improve preservation of heritage at large. The UNESCO chair on Preventive Conservation, monitoring and maintenance of monuments and sites (PRECOM3OS) has pushed research and collaboration to understand the nature of preventive conservation in the field of built heritage. The study of the concepts and practices of prevention in public health helps to understand the systemic nature of prevention and how they can be transferred to the conservation world.

In this study, hardening of calcium hydroxide and calcium silicate binders containing rice husk ash (RHA), cement and lime were studied with mortars. Hardening of these blended binders occurs as a result of combined hydration, pozzolanic reaction and carbonation that occur consecutively. While initial strength development was controlled by the cement hydration, carbonation reaction was favoured at later stage with the decrease in the cement content and increase in the porosity of the blended mortars. Due to their higher porosity, RHA-cement mortars yielded lower strength values than the reference cement mortar. Their compressive and flexural strength increased gradually upon hardening, which indicated a long-term strength development. However, strength reduction was recorded at the very early stage for RHA-cement-lime mortars containing 10%-wt cement. This can be explained by the insufficient cement content and destructive effect of the calcium carbonate crystals on the initially hydrated cement phases as a result of the carbonation reaction. 1.

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In order to study the progress of hydration at early ages in cement-based materials by thermal analysis, FT-IR and XRD, the ongoing hydration reactions should be stopped after different periods of time by complete removal of the free water from the material, i.e. the water which has not yet participated in the hydration reactions. The replacement of the cement paste pore water by a low surface-tension organic fluid is a common technique to stop the hydration prior to thermal analysis. However, it seems that an interaction is taking place between the organic liquid and the cement hydrates which results in the formation of carbonate-like compounds and an underestimation of the real calcium hydroxide content by thermal analysis. The solvent exchange drying technique is studied for different times of storage in the organic solvent and for cement pastes of different ages. TGA and DSC graphs of these pastes are compared with pastes vacuum dried at 2.5×10 -2 mbar.

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