×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Background chloride content of concrete

Background chloride content of concrete

Background chloride content of concrete

(OP)
Tests of water soluble chloride ion, on a sample taken from a core slice 85 mm from the interior face of a perimeter basement wall gave 0.023% water soluble chloride ion by mass of concrete. The result from a core slice taken 85 mm below the top surface of the parking garage floor gave 0.026% water soluble chloride ion by mass of concrete. Both slices were taken from an area that had no signs of leakage and no cracks. The building is in Toronto and was constructed in 1957.

The concrete specialist at the lab is saying this shows the concrete was made with chloride added to the mix. I cannot see how that could be, because if chloride is added to the concrete mix as an accelerator, then the chloride ion content would be much higher than 0.026%. When chloride is added it is at the usual dosages of either 1% or 2% by weight of cement, then my calculation is as follows:

2% "calcium chloride" by weight of "cement" is
1% "chloride ion" by weight of "cement", which is approximately
0.17% "chloride ion" by weight of "concrete".

If added at only 1% "calcium chloride" by weight of "cement" that works out to be 0.085% "chloride ion" by weight of "concrete".

Both of these percentage are well above the 0.026% from the test.

From this I conclude that the 0.026% is indeed the background water soluble chloride ion content of the concrete. This seems not surprising to me because it is known that aggregates from the Niagara escarpment are high in chloride content. Of course I do not know where the aggregates came from in this particular concrete in 1957.

However the concrete specialist does not agree with me, and says that it indicates chlorides were added to the concrete mix. I always ask myself "what if I am wrong"? So I would like to get comment from anyone on this system with relevant knowledge on this issue.



RE: Background chloride content of concrete

Maybe a petrographic analysis will assist in determining the makeup of the concrete and possibly if the aggregates are the source of the Cl- content.

RE: Background chloride content of concrete

AJK1....you are correct. If calcium chloride had been added, you would see elevated water soluble chloride levels beyond what you have. You would also see advanced corrosion of ANY metal items in contact with the concrete.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources