Field and Laboratory Assessment of Lime-Based Mortars

Abstract

Mortar capping trials carried out at Corfe Castle by the National Trust have been monitored closely over the past seven years. These have appraised a range of hydraulic and high-calcium limes. The objectives of the trials have been to explore and promote the materials commonly described in historical literature and used in traditional building practice. A parallel programme of laboratory characterization of the physical properties of similar mixes has been carried out by BRE Limited.The trials were applied to a very high standard of design and workmanship in a context of harsh weather exposure. Good durability is evidenced by the hydraulic limes, mixes of hydraulic and high-calcium limes, and high-calcium lime with sufficient reactive set-additive or pozzolans. High-calcium lime mortars and those with less reactive set-additives showed early failure. These substantiate the claim in most historical literature that the durability of different lime mortars is variable, and it is necessary to specify them according to the demands of the context of application.