Experimental testing of the durability of lime-based mortars used for rendering historic buildings

To find out which render mortar mix shows the best durability properties, we have designed four ageing tests that aim to simulate water movements, ice formation and salt crystallization in lime mortars exposed to an extreme, but realistic, range of temperature and humidity. It has been found that the response of individual mortar mixes differs according to the mechanism and the agent of attack. These findings suggest that in order to provide useful data both the experimental testing approach and the types of mortar tested need to be tailored for the particular circumstance in which the render will be applied.