Frequently Asked Questions
Cement & Concrete
Technology Home > FAQs > Scaling
and Durability
 Q:
My concrete driveway was built last year. This spring I noticed
that there are areas where the broom texture has worn away and in
one area the surface is rough and I can see some of the stones that
I believe to be fairly deep in the concrete. What causes this and
should I be concerned about the long term durability of the driveway?
A: What you are describing may be
scaling, which is a general loss of mortar from the concrete surface.
This mechanism is typically caused by one of the following physical
processes:
- concrete that is exposed to multiple freezing and thawing cycles
when the concrete is saturated with water
- concrete that is exposed to deicing chemicals
In either case the concrete surface is disrupted by tensile forces
that develop as the result of water near the surface which expands
as it freezes. For an existing driveway that is showing signs of
this deterioration mechanism, it is recommended that the concrete
surface be sealed with a high quality breathable sealer, such as
silane, siloxane, or methyl methacrylate. Treating the surface with
a sealer may help to limit the amount of moisture available in the
concrete, potentially slowing or stopping the deterioration.
In extreme cases it may be appropriate to prepare the concrete
for resurfacing and apply a new wearing surface of mortar. Since
it is difficult if not impossible to match the color of the existing
concrete, this method of repair requires that full panels (all of
the area bounded by joints or driveway edges) of the surface be
repaired as one application and in some cases the full driveway
may need to be resurfaced to achieve a consistent color with the
repair.
Left unprotected, concrete that is vulnerable to scaling may have
a shortened service life. However, surface scaling of concrete is
a gradual deterioration mechanism and when addressed with good remediation
strategies the service life of the concrete can be improved. With
reasonable maintenance there is good reason to believe that the
concrete will be serviceable for many years (decades) to come.
Additional information is available in the following references:
Concrete Slab
Surface Defects: Causes, Prevention, Repair (IS177)
Resurfacing Concrete
Floors (IS144)
Winter Weather: Deicers need
not Damage Concrete
Deicer FAQ
More on prevention of concrete scaling.
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