Output details

Sulphate resistance of lime-based barium mortars

Context

The research is concerned with the durability of ancient and historic mortars and how this affects their binder type, composition and microstructure, and the development of novel conservation mortars which present enhanced resistance to polluted urban environments. This is essential for developing future conservation treatments that enable effective management of monuments and historic buildings.

Research

The research resides in the study of original mortars from Byzantine mosaics (Karatasios), and the development of new compatible lime-based mixtures for conservation purposes (Colston). This is the first project to look at the influence of barium compounds on the durability of lime-mortars.

Process

Colston developed the novel scientific concepts and led the research analysis and evaluation. The science involved specialist analytical procedures e.g:

• Determination of pore-space properties by mercury intrusion porosimetry

• Accelerated aging and durability tests using British Standard Methods

• Acid rain simulation tests

Insights/contribution

The research has led to the development of a new conservation mortar that is resistant to the harmful effects of acid rain. The results have evidenced that the formation of a protective layer occurs immediately on contact with acid rain and thus provides effective protection from the degradation process. No previous work has demonstrated barium hydroxide as critical to increasing the service-life of mortar mixtures. This is a major building block in the development of an important new model of treatment of ancient and historic mortars.

Sharing

Research was shared with the conservation and historic buildings sectors through international conferences, seminars and workshops, the HAMR website (www.hamr.blogs.lincoln.ac.uk), and through close engagement of conservators and scientists in the multidisciplinary Historic and Ancient Materials Research forum.

Contributors

This project built on a long-standing, international collaboration between Colston and the Institute of Materials Science at the National Centre for Scientific Research with Demokritos, Kilikoglou and Theoulakis, and doctoral student Karatasios.