A church in Romania built in the Brâncovenian architectural style between 1714 and 1715 is in poor condition and needs restoration work that protects its historic fabric. To help guide that kind of conservation, researchers analyzed fragments of original masonry materials taken from multiple areas, including the entrance, interior walls, and exterior pillars.

In lab prep, the team separated bedding mortar and binder material away from brick and exterior plaster or rendering layers to avoid cross-contamination. Mineral testing found a consistent pattern across samples: quartz and feldspathic minerals in the aggregate, and calcite as the main binder component. Elemental results also showed a split between inside and outside. Interior samples carried much higher calcium oxide content, while exterior samples had relatively more silica, aluminum oxide, and iron oxide, which the researchers tied to long-term exposure and weathering.

The big takeaway for restoration pros is how the mortar sets. Thermal and microstructural testing pointed to an air lime mortar, not a hydraulic binder. Results indicated portlandite and carbonation products like calcite, with no signs of hydrated silicate or aluminate phases that would signal a hydraulic or cement-rich system.

For mason contractors and preservation teams, this supports a familiar field lesson: compatibility beats strength. The study warns that highly hydraulic or cement-rich repair mortars can create stiffness and moisture-transport mismatches at the interface between new and historic work, which can speed up deterioration. It also showed that exposure conditions matter. Exterior elements experienced greater chemical and physical change over time, driven by freeze-thaw cycles, moisture infiltration, and biological colonization. That means repair mortar selection, and expectations for performance, should reflect whether you are working inside protected areas or on exposed piers and façades.

Read the full, original article from Bioengineer.org here.