Concrete cancer often occur in coastal areas where sea salt can cause unwelcome reactions in brickwork, mortar and concrete slabs.
Efflorescence is a powdery white salt deposit that can form on cement-based products like bricks, mortar and sometimes concrete. It usually appears when dry, hot weather follows a period of cool wet weather. Evaporation of surface water draws out salt from porous products like bricks which settles on the brick surface. Firmly brushing the powder off the brickwork is the best solution, but in difficult situations extremely diluted hydrochloric acid can be used to eradicate the efflorescence.
Concrete cancer is a problem where wind borne salt or carbon dioxide can penetrate into the pores of the slab, causing deterioration of the concrete and corrosion of steel reinforcement. This is a more serious problem than normal shrinkage cracks and often results in crumbling concrete and rusting steel rods, thereby reducing concrete strength.
Affected concrete surfaces can be treated and replaced or a protective coating can be added prior to construction to prevent this problem occurring.