The coupling effects of freeze-thaw cycles and salinization due to snowfall on the rammed earth used in historical freeze-thaw cycles relics in northwest China

Abstract

Rammed earth, a kind of building materials used worldwide because of its straightforward manufacture and low cost, is still used in the construction industry today. Many rammed earth architectural relics are preserved in the arid and semi-arid areas in northwest China. In this area, the winter snowfall process is generally long and may work to degrade the physical and mechanical properties of rammed earth, destroying these relics. Therefore, to protect rammed earth sites, it is very important to understand the mechanisms governing rammed earth deterioration during snowfall. Using real-time monitoring and soluble salt testing of the temperature and water content of the rammed earth at three representative sites in the north-west region, we found that snowfall leads to varying degrees of freeze-thaw cycle and salinization coupling that degrade rammed earth structures. Wind erosion, disintegration, shear and mercury intrusion experiments using remoulded rammed earth samples were performed based on the monitoring results and incorporated different types and concentrations of soluble salts; three freeze-thaw cycles were applied to explore the macro and micro changes in the wind erosion modulus, disintegration speed, cohesion, internal friction angle and pore size of the rammed earth samples. Finally, the joint analysis of the monitoring results, macroscopic property indices and microscopic property indices revealed the mechanisms of rammed earth degradation due to the observed coupling effect.