Testing properties governing the durability of lime-based repair mortars

Lime‐based mortars ‐ are preferred for the repair of historic structures, where they were used in the construction of the original. The long‐term performance of repair lime mortars is closely related to durability issues, concerning the old structure’s substrate, the new repair mortars and the interface between the two, which is also much influenced by the technique of mortar’s application.

Durability is a multifunctional property affected by a number of parameters, including local environmental conditions. However, experience shows that some characteristics of materials play a dominant role for assessing the durability of repair lime mortars and have a direct impact on the longevity of the repaired structure. This paper presents a review of research; case studies and Master/PhD projects supervised by members of the RILEM TC 277‐LHS. Through this review we evaluate research and common practice concerning durability challenges and attempt to answer questions arising when assessing the durability of repair lime mortars including: 1) The most often encountered failures, due to inadequate mortar durability, 2) The characteristics of mortars that influence durability, 3) The methods used for testing the durability of lime‐based mortars, with an evaluation of their applicability and performance, 4) The importance of quality control and on‐site execution practices.