Time-Dependent Deformations of Lime-Based Mortars and Masonry Specimens Prepared with Them

Lime-based mortars are preferred in repairing interventions of Historic Masonries (HM), which are the bearing elements of old structures, since they are considered compatible with the existing mortars. In historic castles, towers and particularly in cases of thick mortar joints reconstruction, long term deformations are of great interest for the structural stability of the repaired monuments. The exposure of lime-based mortars to drying and sustained loading influences both phenomena of shrinkage and creep. In this experimental work, the behaviour of different composition mortars (based on hydrated lime, lime-pozzolan, hydraulic lime and lime+pozzolan+cement) have been studied under sustained load by using spring-loaded creep frames. The same types of mortars were also used for the masonry specimens with traditional roman type bricks in successive layers. All specimens, mortar prisms (4×4×16) cm and masonry specimens were placed in a moisture-controlled room of RH 55–65% and 20 °C temperature. Bricks and mortars’ compressive strength have been separately estimated by crushing proper samples. Deformations were recorded for more than 6 months because of drying and sustained loading. It seems that the strain measured is higher than in the case of cement-based mortars/ concretes. Furthermore, for thick joints the composition of mortar and its quality, expressed as compressive strength play a crucial role in the total deformation measured apart from the sustained load value. In addition, the rate of creep evolution and the order of creep magnitude are indicated.