RILEM TC 277-LHS report: a review on the mechanisms of setting and hardening of lime-based binding systems

30 pags., 5 figs., 1 tab.The main objective of RILEM TC LHS-277 “Specifications for testing and evaluation of lime-based repair materials for historic Structures” is the revision, adaption and, when necessary proposal, of the test methods to accurately study lime-based binding systems and mixtures, such as mortars and grouts. The empiric use of the lime-based composites and the predominant employ of cement in the field of Civil Engineering have led to the widespread application of test methods developed for cement-based composites to test the former. However, the clear differences in composition and performance between modern cement binders and lime-based materials would advise to explore specific test methods for the latter. To undertake this task the previous knowledge on the mechanisms of setting and hardening of these binders must be revised, arranged and synthesized. Processes such as drying, carbonation, hydration and pozzolanic reaction may occur during the setting and hardening of lime-based mortars and competition between them cannot be underestimated. With the aim of underpinning the revision and proposal of test methods for lime-based systems, this review paper reports a comprehensive study of the mechanisms of setting and hardening of these binders, considering the variability of the composition, which includes pure air lime as well as lime with hydraulic properties, lime-cement and lime-pozzolan systems

TESTING PROPERTIES GOVERNING THE DURABILITY OF LIME-BASED REPAIR MORTARS

Lime-based mortars seem to be preferred in repairing historical structures. The long-term performance of lime-based repair mortars is closely related to durability issues concerning the old structure substrate, the new repair mortars and the interface between the two aforementioned materials, which is also much influenced by the technique of mortars application. It is well known that durability is a multifunctional property affected by a number of parameters, including local environmental conditions. However, experience (based on research and survey of real case studies) showed that some of the parameters concerning the characteristics of materials play a dominant role in assessing the durability of repair lime-based mortars and have a direct impact on longevity of the repaired structure. This paper presents comments of review papers concerning research publications or case studies, as well as Master or PhD theses supervised or carried out by the members of RILEM TC 277 LHS. Through the review and evaluation of research and common practice concerning durability challenges, we anticipate to find answers to questions arising in assessing the durability of repair lime-based mortars, such as: the most often encountered failures due to mortar durability inadequacy, the mortar properties/characteristics that seem to be influential on durability, the test methods used for testing the durability of lime-based mortars and comments related to their applicability and performance and the importance of quality control and on site execution practices