Radiocarbon Dating Methodologies for Historical Mortars

Radiocarbon dating of historical mortars has emerged as a pivotal tool for dating built heritage, offering direct chronological insights into construction phases where organic materials are scarce. Mortars comprise a calcium carbonate binder formed by carbonation of lime, embedding atmospheric carbon-14 at the time of hardening. However, accurate age determination necessitates the isolation of this anthropogenic carbonate from secondary geological sources and contaminants such as reprecipitated calcite or limestone fragments (“dead carbon”), which can bias dates towards older values. Multi-analytical protocols now integrate mineralogical characterisation, petrography, stable isotope analysis and advanced separation techniques to assess sample integrity and extract a pure binder fraction. Thermal fractionation methods, including ramped pyrolysis, enable identification of coherent temperature intervals reflecting a single carbonate source. Complementary spectroscopic methods, notably ATR-FTIR, permit rapid screening of calcite origin prior to destructive testing. When coupled with accelerator mass spectrometry, these approaches yield high-precision radiocarbon ages that align with historical records and architectural typologies. Bayesian statistical frameworks further refine chronologies by integrating multiple mortar dates into construction models, enhancing interpretations of building sequences, restoration episodes and regional construction dynamics. The global application of such methodologies has advanced our understanding of heritage conservation, underpinning restoration strategies and informing interdisciplinary narratives of architectural evolution.

Research from Nature Portfolio

A multi-analytical screening procedure has been developed to improve the reliability of mortar dating by systematically characterising complex samples and isolating the pure carbonate binder. This workflow combines mineralogical and petrographic assessments with X-ray diffraction, scanning electron microscopy and stable isotope measurements to evaluate sample suitability prior to radiocarbon analysis. Optical cathodoluminescence maps are used to detect recrystallised calcite domains, while isotopic ratios confirm anthropogenic signatures. Applied to medieval churches in Northern Italy, this approach demonstrated successful 14C dating of binder fractions, yielding age estimates consistent with historical chronologies and illustrating the potential of integrated characterisation to deconvolute mixed carbonate sources in challenging architectural contexts.

Radiocarbon Dating Methodologies for Historical Mortars publication trend

The graph below shows the total number of articles in radiocarbon dating methodologies for historical mortars across all publications each year (not limited to Nature Index journals).

Technical terms

Radiocarbon dating: measuring the decay of carbon-14 isotopes to determine the age of carbonate materials.

Carbonate binder: calcium carbonate component precipitated in mortars that incorporates atmospheric carbon during hardening.

Ramped pyrolysis: progressive heating of samples to separate binder fractions by temperature for more accurate 14C analysis.

ATR-FTIR spectroscopy: non-destructive infrared technique to distinguish anthropogenic and geogenic calcite in mortar samples.

Accelerator mass spectrometry (AMS): high-sensitivity method for measuring low concentrations of radiocarbon in small sample fractions.

References

1. Ramped pyrolysis radiocarbon dating of lime lumps: Establishing the earliest mortar-based construction phase of Turku cathedral, Finland. Journal of Cultural Heritage (2023).
2. Integrated multi-analytical screening approach for reliable radiocarbon dating of ancient mortars. Scientific Reports (2022).
3. Evaluation of ATR-FTIR spectroscopy for distinguish anthropogenic and geogenic calcite.. Journal of Physics Conference Series (2022).
4. Radiocarbon dating of lime plaster from a Roman period cistern in ancient Gerasa, Jerash in Jordan. Journal of Archaeological Science Reports (2022).
5. The State-of-the-Art of Dating Techniques Applied to Ancient Mortars and Binders: A Review. Radiocarbon (2020).