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Old 08-28-2010, 03:15 PM   #1
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Salt Damaged concrete sidewalk


I used salt to melt the ice on my sidewalk this past winter. It left the sidewalk pitted. The damage is minimal but is there anything I can do to fix it?

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Old 08-29-2010, 08:20 AM   #2
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Salt Damaged concrete sidewalk


TRACKER, what you can do to fix the pitting you have from the salt damage is use a hydralic cement to patch the holes. Make sure the holes are clean from debris and mist slightly before applying the hydralic cement. That way you will get better bonding with the product. It's not going to be an exact match in product, but this should help. Also for ice control on cement, you should consider using calcium chloride instead. It's safer to use on concrete.

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Old 08-29-2010, 08:54 AM   #3
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Salt Damaged concrete sidewalk


Yeppers calcium chloride for concrete.
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Old 10-27-2011, 08:13 PM   #4
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Salt Damaged concrete sidewalk


Any kind of chloride is going to be acidic, and that is where the problem is. Concrete is an alkaline substance, and salt and ice-melting chemicals will slowly break it down. What you can do to prevent this from happening anymore is put down a penetrating permanent sealer. Coatings and top sealers will get you through one or two winters, but a reactive silicate type of penetrant will last for the life of the concrete. And extend the life of the concrete to boot!

There are just a few of this type of permanent sealer out there, and the one I have personally used and support is called CreteDefender. If you want to get more info on how concrete goes bad and the benefits of this type of sealer, go to: http://cretedefender.com/how-concrete-goes-bad/ . There is a wealth of information on this site regarding why concrete fails and what we can do to prevent it.

Hope this helps! Get a reactive silicate down before winter comes!

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Old 10-27-2011, 09:14 PM   #5
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Salt Damaged concrete sidewalk


Keithdb, I might actually put some stock in your comment if you didn't start out claiming that Any kind of chloride is going to be acidic. This is totally incorrect. Typical salt, NaCl, has a pH of essentially 7, meaning that ordinary salt is neutral. The same is true for any salt composed of an alkali metal such as potassium or sodium, and either fluorine, chlorine or bromine.

Chloride attack on concrete is very real, but is complicated, and has nothing to do with the pH of the solution.
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Old 10-27-2011, 10:39 PM   #6
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Salt Damaged concrete sidewalk


Okay, Dan- I guess I was simplifying a bit, because this is a DIY forum! Didn't think I'd have an engineer challenging my choice of words!

The proper statement would be, any kind of chloride is more acidic than concrete. Concrete has a ph of around 11, and chlorides come in at 5-7. Contrary to your statement, Dan, ph has quite a bit to do with concrete degradation. Chloride will penetrate into the concrete as it is carried in through the water, and the more acidic makeup will draw down the ph level and widen the pores over time. This allows more water penetration, and the freezing and thawing of this water in the pores is the primary cause of the surface delamination, which is the spalling or popping effect that TRACKER is referencing.

Calcium chloride is indeed a better choice, but only slows the degradation... buying a little more time before the integrity of your concrete is ruined!
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Old 10-28-2011, 07:16 AM   #7
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Salt Damaged concrete sidewalk


The advantage of calcium chloride over sodium chloride is that the former, pound for pound, lowers the freezing point of the water (solution) more and thus reduces the number of freeze thaw cycles.

The disadvantage of calcium chloride is that the pH of the solution is lower (more acidic relative to sodium chloride).
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Old 10-28-2011, 07:46 AM   #8
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Salt Damaged concrete sidewalk


Chloride attack on concrete has nothing to do with acidity. I suggest reading the following article for a full discussion about causes and cures to concrete degradation: http://www.heritage.nsw.gov.au/docs/Concrete_Part_1.pdf

I have excerpted two paragraphs that deal with chloride attack and carbonation.

Carbonation occurs when atmospheric carbon dioxide
reacts with the pore water in the concrete creating
carbonic acid, which reacts with the lime in solution
(Ca(OH)2 reducing the alkalinity of the concrete from
12.5 to less than 9.0. Carbonation is not harmful to
concrete but when the carbonation front reaches the
level of the steel reinforcement, corrosion will
commence.

Chlorides may have been added to the concrete at the
time of construction as a calcium chloride accelerator
(used in cold weather, or to speed up turnaround of
moulds and formwork), or cast in from poorly-washed
marine aggregates, or may have ingressed from sea
water, wind-blown marine spray or saline groundwater.
Chlorides attack the passive oxide layer of the steel but
do not affect the alkalinity of the concrete.


I realize this is a DIY forum and this article may be on the technical side, but I get irritated when completely inaccurate explanations for problems are posted as fact. The remainder of the paper deals with additional sources of damage to concrete, methods to control damage, and techniques to extend the life of historic concrete structures. Good reading. Applicable to all concrete structures, reinforced or not.

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