Analysis and characterization of modern and ancient mortars

Abstract

The analysis, characterization, and comparison of modern and ancient mortars provide fundamental (by tracing the change in the raw materials and recipes used from the past to the present) and practical (obtaining modern mortars compatible with the ancient) knowledge. This work aimed to characterize modern and ancient mortars by investigating their phase composition, binder-to-aggregate ratio, hydraulicity, and hygroscopic properties. The used methods for analyses were powder X-ray diffraction, Fourier transforms infrared spectroscopy, and thermal analysis. A modern mortar (sample A) preparation was with a binder of white Portland cement and an aggregate of river sand. Ancient mortar samples (sample B - cocciopesto and sample C - lime mortar) collection were from Bulgarian archaeological sites allocated within the Roman period. The results define investigated sample A as pozzolanic mortar with hygroscopic properties, sample B - as hydraulic lime mortar with hygroscopic properties, and sample C – as lime mortar without any hygroscopic properties. Obtained results with these, achieved for phase composition and binder-to-aggregate ratio, show that modern mortar is not compatible with the Romans and is not suitable for reconstruction and conservation of masonry from these archaeological sites.