A report on two research projects. RTU/4 carried out studies on the structural stabilization of old masonry and rock structures using various filling materials; four progress reports were produced in 1980: definition of the terms of reference, test methods, materials, and fluidifiers or water reducers. A second phase of mortar research, begun in April 1980, involved the prep-aration of lime mortars with several additives to improve their setting time and hydraulic properties. The tests of these materials are described in a progress report. -- AATA