20th Century Mortars: Physical and Mechanical Properties from Awarded Buildings in Lisbon (Portugal)—Studies towards Their Conservation and Repair

Abstract

This paper addresses the study of renders and plasters’ physical and mechanical characteristics from selected buildings awarded during the 20th century with a renowned architectural prize in Lisbon, Portugal. The characterisation was done to understand mortars’ physical and mechanical properties and their evolution during the 20th century. These characteristics will also help determine compatibility requirements for future conservation and restoration interventions. Since these buildings have a heritage great interest status, the need to preserve them is a paramount issue. Fifty-three samples from nine case studies were studied via capillary water absorption, drying rates, open porosity, dynamic modulus of elasticity, and compressive strength. There were limitations in sample collection due to the buildings being in service and technical constraints regarding sample quantity for testing and separating layers of the multi-layer mortar system. Nevertheless, the results showed different ranges of quantitative values for these tests, whether the mortars were lime, gypsum, cement-based or had lime–cement blended formulations.