| Snow and ice can be removed with normal hand
equipment or motorized vehicles. Snow plow blades should be equipped with a rubber edge
and set @ 1/4" above the pavement. Rotary brushes and snow blowers can also be used.
The use of rock salts are not recommended for snow and ice removal because of the
possibility of efflorescence. Non-sodium de-icers that are environmentally compatible are
available as well as sand or cinders for traction control. EFFLORESCENCE
Efflorescence is a crystalline salt deposit on the surface
and in the pours of concrete, masonry, and other building products. A phenomenon reported
as early as the 1870's and much studied since, it can appear as sulphate and carbonate
compounds of sodium, potassium, calcium, magnesium and aluminum. Chlorides may also occur
as efflorescence. This is usually a result of the use of calcium chloride as a mortar
accelerator, contamination of masonry components(including sand) by sea water or the
improper use of hydrochloric acids in cleaning solutions.
There are several sources for efflorescence:
1) the movement of groundwater that moves upwards, by capillary action or
"wicking", into masonry or concrete materials. 2) salts in the soil that are in
contact with paving can migrate above grade. 3) natural-state salts that are found in
mortar, concrete or other building products. Although rare, some raw material used to make
clay brick contain small amounts of salt. However, these small amounts are minor compared
to studies that found two to seven times as much soluble material in concrete products
versus fired clay material. W.E. Brownell concluded in his research study
that the most common form of efflorescence comes from the "migration of 'free-alkali'
solutions from the mortar to the brick". This would also be true for any newly
poured concrete curb, foundation or sub base slab.
Efflorescing salts dissolve in water and
are absorbed into the masonry pours. Typically, clay bricks can absorb 5% to 8% of their
weight in water. Heat from the sun (or other source) begins to draw the moisture to the
wall surface and as the water completely evaporates, the salt deposits are left on the
surface.
Since humidity and moisture play a key role in the
efflorescence process, some areas of the country will be affected more than others.
Seasons will play a role as precipitation during season changes will increase the
likelihood of efflorescence.
The most important solution to solving
efflorescence is finding, locating and dealing with the source of water.
Since the source of water in a paving application is generally clear, the most important
factor in limiting the occurrence of efflorescence is insuring adequate drainage of the
pavement through grading or specific drainage systems. Good drainage will keep the pavers
dryer and thus, they will be less likely to effloresce.
While efflorescence control systems are available, they
don't guarantee full arrest of the problem and tend to be expensive. The best thing to do
is to allow the efflorescence to run its course provided that the paved area has good
drainage. The main reasons for this recommendation are as follows: the source of the salt
is most likely coming from base materials or mortar. In a flexible base application, after
6 months, 90 % of the water will run off the paving surface and away from the pavers
versus down through the joints. This change should carry the salts in solution into the
ground rather than into the pavers. In all cases, free salts dissipate eventually and the
problem goes away for good, generally within 18 months.
As a general rule, the removal of efflorescing
salts from the face of masonry is relatively easy operation. Efflorescing salts
can be removed with dry brushing or with clear water and a stiff brush. |
