Author
ADAMI, C.-E
MSc Structural Engineer, NTUA, Faculty of Civil Engineering-Laboratory of Reinforced Concrete, adamis@central.ntua.gr
VINTZILEOU, E
Professor, NTUA, Faculty of Civil Engineering-Laboratory of Reinforced Concrete, elvintz@central.ntua.gr

Abstract
This paper summarizes the results of an experimental programme carried out at the National Technical University of Athens (NTUA), with the aim to assess the effectiveness of grouts with medium or low mechanical properties in repairing/strengthening historic structures by investigating the bond properties along interfaces between grout and in situ materials. For this purpose, more than 300 interfaces between various substrates and hydraulic grouts (cement-lime, ternary or hydraulic-lime based grouts) were tested either in tension or in shear. The experimental results allow for the effect of properties of both substrate and grouts to be evaluated. The main finding of this experimental programm is that ternary and hydraulic-lime based grouts exhibit improved bond properties, compared to cement-lime grouts. Thus, it is proven that grouts with medium or low mechanical properties, when appropriately designed, offer a reliable and efficient alternative to cementitious grouts for retrofitting of historic masonry structures. Finally, on the basis of the experimental data, constitutive laws for the bond mechanism were developed, for use in modelling of interfaces.

Key words
historic masonry structures, hydraulic grouts, bond, constitutive laws, FE modelling