New chronology of medieval objects in the Northern Black Sea region according to the method of determining calcite main peak intensity

Abstract

Determining the ancient architectural and cultural monuments’ age is an important scientific problem. The article presents the results of the ancient brickwork lime mortars study. The portlandite transformation mechanism, which initially constitutes the basis of lime mortar, into calcite is shown. It has been established that this process takes from 100 to 200 years under natural conditions and the speed of this process is influenced by temperature, humidity, peculiarities of interaction with carbon dioxide contained in the air, etc. The examples showing that portlandite is completely transformed into calcite in masonry mortars of the 18th century, and that portlandite has not been found in older mortars are given. It was determined that after portlandite transition to calcite with increasing age, an increase in the calcitere crystallization degree is observed and this is manifested in a higher intensity of calcite peaks (especially the main peak 3.03 Å), increase in the crystallinity index - the width of the peak at half maximum (FWHM) or the main peak integral width, that is, the ratio of the area to the height of the peak above the background. Factual data, which show that in older lime solutions the degree of recrystallization of calcite is higher than in younger ones, are presented. This moment makes it possible to indirectly determine the relative age of brick and masonry of various monuments with architectural heritage, which is especially relevant for the South of Russia, where the objects have been preserved using lime mortars of the northern provinces in the Byzantine ecumene and other periods of various cultures.