We have recommended this publication on our blog previously:
Salt attack is as destructive to masonry as termites are to timber, and is prone to occur on any building site in Australia due to our soils and extreme weather patterns. As salt is dissolved by water and absorbed by masonry, the water evaporates, leaving behind more and more salt with each wet cycle. Salt crystallises to expand at extraordinary pressure (> 200MPa) to easily turn stone, bricks and mortar to dust.
As outlined in the guide, it is incredibly important to use "sacrificial mortars" when repointing heritage work and older buildings. Weak lime mortars are hygroscopic, and serve to 'poultice' salt damp away from critical building fabric such as face bricks and stone. Efflock should not be used in re-pointing work unless the mortar can be installed across the full width of the wall to form a complete DPC (Damp Proof Course).
However, Efflock is ideal as an additive for new construction to bulk impregnate the mortar to avoid the same long term problems. Given that the DPC is often located 500mm above ground level, the masonry below the DPC will absorb rising damp and salts and is likely to result in major damage over time. By including Efflock in the first 3 courses of brickwork (to allow for varying finished ground levels), provides a DPC at ground level, providing ideal way to control rising damp and salt attack by minimising the height of the evaporation point. Most importantly, always ensure your bricks are Exposure Grade, which are tested and certified resistant to salt attack.
Efflock is also ideal as an additive for render, and should at least be employed for render below the DPC. This will prevent unsightly paint blistering due to salt attack. (Remember salt attack can sill occur on the inside face of the wall, so using efflock in the mortar bed joints as a DPC is still recommended practice for rendered walls.)
Above: Salt attack below the DPC. Notice the mortar is actually more durable or less porous than the bricks, and therefore has absorbed less salt and has suffered less damage.