Potential application of bio-admixtures in synthesizing traditional lime binders- A comprehensive review

Ancient lime mortar and plaster recipes are observed to be highly superior in terms of performance and durability, known from the era of Roman concrete. Bio-admixtures (organics) of different characteristics are a certain ingredient in ancient lime binders. However, their preparation, concentration, role of action, influence on properties of lime binders are only partially acknowledged. Inadequate documentation is solely responsible for the lack in knowledge on the additives used and their role of action. The understanding on the bio-additives used in ancient time is essential to develop similar repair materials compatible to heritage structures. The addition of bio-admixtures to lime is reported to enhance the workability, mechanical properties and durability against weathering mechanisms such as salt crystallisation, acid-alkali attack depending on the composition and dosage. Therefore, identifying the organics used, their reaction mechanisms and effect on fresh, mechanical and durability properties are essential to create binders that are suitable for repair. The current work is a collection of data available for the organics widely used, dosages, and techniques to identify their composition, preparation methods and their influence on performance of lime binders. Comprehending these parameters will aid in developing superior performing mortar and plasters for heritage repair and further be commercialised as well.