I have a brick walkway about 10 years old leading from my porch to the
street. The first half is under a carport, the rest in the open. We
never had efflorescence before. Since the recent heavy rains in L.A.
there is a huge volume of it on the bricks and a little on the concrete
driveway under the carport, which was mostly dry, and none in the open
areas. Can anyone say why this would be happening now? I am brooming it
off often, but it comes back as thick as light snow. I'm debating using
dilute acid, but I'm not sure that will solve it. Thanks.
As other posters have noted, www.bia.org has a good summary of causes of
Heavy rains are indeed the cause, as with unusual rains comes reactivation
of groundwater flow, and fomation of springs that may or may not be long
lasting. Springs themselves can carry salts that evaporate out at the brick
surface, leaving soluable salts behind. The water flow can also dissolve
salts from whatever base was installed as an underlay for the walkway. If it
is mortared, the salts may well com from mortar or underlying cement, but
could also be from many other sources. Even the groundwater itself may be
hard, leaving salt crystals on the surface.
Overall, it is mostly a nuisance. Just keep the brick swept, and wash it off
with a nozzle from time to time. I wouldn't use acid.
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