Degradation of rammed earth under soluble salts attack and drying-wetting cycles: The case of Fujian Tulou, China

• Published in: Applied clay science 2021-10, Vol.212, p.106202, Article 106202
• Main Authors: Luo, Yi, Zhou, Peisong, Ni, Pengpeng, Peng, Xingqian, Ye, Junjie
• Format: Article
• Language: English
• Subjects: Crystallization; Deterioration; Drying-wetting cycles; Rammed earth; Salt
• ISSN: 0169-1317; 1872-9053
• DOI: 10.1016/j.clay.2021.106202

Rammed earth is a common construction material for thousand years throughout the history of human civilization. The strength degradation of rammed earth under salts attack and drying-wetting cycles needs to be assessed. In this study, chemical analyses were conducted on rammed earth materials sampled at different wall heights from a demolished Fujian Tulou for the measurements of salinity. The degree of salinity was found to increase from the top to the bottom of the wall. To better understand the salt effect, sodium chloride (NaCl), sodium sulfate (Na2SO4), and calcium chloride (CaCl2) were mixed in various contents with desalinated soils to produce remoulded specimens for strength tests. The unconfined compressive strength (qu) and the cohesion (c) were reduced with the increase of the salinity degree. The influence of single salt attack was not apparent on the variation of qu or friction angle φ, but it was significant on the cohesion variation. The soil attacked by Na2SO4:CaCl2 = 1:1 mixed salt had the lowest qu and c values. The Ca2+ cations from CaCl2 salt reacted with the SO42− anions from Na2SO4 to form crystals with increasing volume, leading to strength deterioration in rammed earth materials. •Degree of salinity for ancient rammed earth walls decreases with the wall height.•Cohesion of remoulded rammed earth reduces with the degree of salinity.•Influence of single salt attack is significant on the variation of qu and cohesion.•Attack of mixed salt of Na2SO4:CaCl2 = 1:1 causes the lowest qu and c.•Crystallization between Ca2+ cations and SO42− anions causes strength deterioration.