ABSTRACT
Since ancient times, lime based binders such as high calcium lime, lime with pozzolana and hydraulic lime have been successfully used in construction and have proven their long-term durability. Towards the end of the 19th century, development in the building industry and increase in the construction needs encouraged the search for stronger mortars with more rapid hardening. This eventually induced the development of the Portland cement which became a dominant binder in the construction industry after that period. This has inevitably led to the replacement of lime based binders with the cement in conservation practices, which has resulted in serious damaging mechanisms related to the incompatibility of cement in chemical, physical and mechanical properties when used together with ancient building materials. There exist evidences that stronger mortars can reduce the durability of the masonry whereas mortars with low compressive strength like lime mortars can increase the durability of the masonry in the long-term (Van Hees et al., Van
Balen et al. 2005). In spite of this, addition of cement to lime based mortars is still a common practice in most of the conservation works in order to promote the hardening reaction by cement hydration, to shorten the construction time and to increase the strength of the mortar. However, certain mortar compositions with lime and cement may cause lack of strength development and durability. The main objective of this study is, therefore, to investigate the influence of the cement addition on the strength development, porosity and microstructure of the lime mortars, and to understand the hardening reactions.This will provide fundamental insight while defining the compatibility requirements for repair mortars.
