Building and Civil engineering Institute ZRMK, Centre for Materials and Structures, Ljubljana, Slovenia
University of Ljubljana, Faculty of Civil and Geodetic Engineering, Chair for Research of Materials andStructures, Ljubljana, Slovenia


The field of strengthening stone and mixed stone-brick masonry walls by means of grout injection in general, but especially in case of strengthening of heritage buildings walls, needs technical regulations that would define the methodology of work and criteria for achieving the required quality. The aim of the paper is to contribute to the development of guidelines in this field, based on results of laboratory tests.
The tests carried out were divided in four parts. In the first part the contents of potentially harmful substances for nine different dry injection grouts were analyzed. In the second and third part, properties of fresh and hardened grouts were determined. In the fourth part, cylindrical specimens that represented internal cores of injected walls were tested and their mechanical parameters were evaluated. Based on the obtained test results, chemical, physical and mechanical criteria for selecting optimal grout mixture were given and the tested grouts were classified in three classes. Criteria for different classes were determined through literature survey and in collaboration with conservators and producers of grouts. Finally, guidelines and research needed to assess the condition and type of walls that could be strengthened by means of grout injection technique and to ensure the quality of executed work, are presented.

Key words
grout injection, heritage buildings, strengthening, guidelines