Design and evaluation of restoration mortars for historic masonry using traditional materials and production techniques

摘要

Cement based mortars used for historic masonry restoration presented unsatisfactory results, due to their chemical and physico-mechanical incompatibility to original buildings. In the present research, several syntheses of restoration mortars are produced using traditional techniques and materials such as binders (aerial and natural hydraulic lime), pozzolanic additives (natural and artificial pozzolanas) and aggregates (sand and crushed brick). The technical characteristics of the mortars were determined using mechanical tests (compressive and flexural) and mercury intrusion porosimetry measurements at the time of 1, 3, 9, 15 months of curing. Water absorption measurements were performed at the time of 9 and 15 months curing, in order to evaluate mortars microstructural characteristics, their rate of water absorption and the total percentage of absorbed water. The aerial lime - artificial pozzolana mortar presented the best mechanical and microstructural performance. Hydraulic mortars acquired the maximum of the mechanical strength in 1 month, lime - pozzolana mortars in 3 months while aerial lime mortars continue to gain mechanical strength even in 15 months curing. Furthermore, the use of ceramic aggregates produces lightweight and elastic mortars, compatible to historic ones.