Case 4

Cause of Defects

The mechanisms of lime leaching are often caused by water penetration. Simply stated, water-soluble salts in solution are brought to the surface of the tiles and deposited there by evaporation. The salt solutions may migrate across surfaces of units, between the mortar and units, or through the pore structure of the mortar or the clay bricks.

There are certain simultaneous conditions which must exist in order for lime leaching to occur. Soluble salts must be present within the free cement in mortar. There also must be a source of water and it must be in contact with the salts for sufficient time to permit them to dissolve. The masonry must be such that the migration of salt solutions to the surface, or other locations, occurs in an environment which is conducive to the evaporation of water.

Possible sources of water:

The primary source of moisture for the occurrence of efflorescence is rain water which penetrates or comes in contact with mortar. Water film adheres to the external surfaces of wall and migrates via capillarity through the brickwork.

The presence of this free water in mortar joints could lead to the dissolution of alkaline salts available. Upon drying lime from the mortar is brought to the surface.

Consequence

Persistent efflorescence should be taken as a warning that water is entering the wall and this may cause deterioration of wall materials and have other consequences. If repairs are not done to the localised portion of efflorescence formation, further tile delamination may occur.