Chemical resistance of pozzolanic plaster for earthen walls

Earth is an economical and ancient construction material. Historical earthen architecture is a heritage that must be handed over to the next generations but experience shows that these historical structures do not stand up well against the destructive action of rain. In this study, fly ash, powdered brick, hydrated lime and water were mixed to develop a pozzolanic plaster for use in conservation of earthen walls. Chemical durability, such as sulfate, salt and acid resistance of this pozzolanic plaster also was investigated. The chemical compounds employed in these tests were 2000 and 5000 ppm sodium sulfate and ammonium nitrate solutions for sulfate and salt attack. Also, the acidic media were with 1%, 5% and 10% concentrations of sulfuric acid and hydrochloric acid. All test results indicated that incorporation of fly ash in pozzolanic plaster provides a satisfactory resistance to aggressive chemicals such as sulfate, salts and acids. The developed plaster seems to be a suitable material for preservation of earthen walls since it has adequate mechanical and chemical properties in comparison with soil.