Tailoring the binder matrix of lime-based binders for restoration interventions with regard to mechanical compatibility

Abstract

Lime-based binders have been extensively used for restoration interventions and have successfully addressed different performance and compatibility requirements. Lime (aerial or hydraulic) is commonly used in combination with pozzolanic admixtures or cement, to comply with both, chemical/mineralogical and mechanical compatibility criteria. The goal of the present investigation is the production of binder matrices with tailored mechanical properties according to the above criteria. The first binder was a binary paste consisting of natural hydraulic lime and metakaolin and the second was a ternary matrix consisting of hydrated lime, cement and metakaolin. The flexural and the compressive strength of the binary paste were 1.6 MPa and 6.1 MPa, respectively, while the use of cement in the ternary mixture increased the flexural and the compressive strength at the values of 2.5 and 8.5 MPa, respectively. Mechanical properties of several lime/metakaolin binders and lime/cement binders were collected from the literature to establish approximations correlating the binder composition to the mechanical response. The proposed approximations can be used as guidelines for facilitating the design of modern conservation binders based on mechanical compatibility and binder composition parameters, according to the requirements of the individual restoration project.