Technical University of Denmark, Department of Civil Engineering

Presence of salt in porous materials can result in deterioration. The volume change from dissolved salt (ions) to precipitated salts results in a crystallization pressure. When this crystallization pressure occurs underneath the surface deterioration of the overlying material can occur. For the present investigation a mortar representing a typical historic Danish lime mortar was designed and used together with bricks produced for restoration purpose. A lime mortar with a grain size distribution close to the standard grain size distribution and a lime to aggregate ratio of 1:3 was chosen. The results from electrokinetic desalination of the species with the size of 5 cm × 5 cm × 11 cm showed continuously reduction of the initial chloride and sodium content of 0.37 wt% and 0.22 wt% respectively to 0.0054 +/- 0.0054 wt% for sodium and below the detection limit for chloride by application of 20 mA for six days. The interface transition between brick and lime mortar did not seem to have an effect on the desalination and no accumulation in the lime mortar was measured.

Key words
Brick, design of a historic lime mortar, non carbonated lime mortar, electrochemical desalination, sodium, chloride