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What is the difference between a control joint and a contraction joint in concrete? I mean, a control joint is to control the cracks in concrete due to temperature or shrinkage etc... I understand it. But then what is a contraction joint? I saw this term when I was reading about dams, when they pour large concrete masses and make contraction joint to account for shrinkage. Why don't they also call it a control joint?

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  • $\begingroup$ Perhaps they mean the same thing... what are the sources you used and how did both sources define the terms? $\endgroup$ – Solar Mike May 9 '20 at 6:28
  • $\begingroup$ Are you familiar with construction ? $\endgroup$ – user3600630 May 9 '20 at 9:33
  • $\begingroup$ Yes, are you? But given your question with no sources... $\endgroup$ – Solar Mike May 9 '20 at 10:04
  • $\begingroup$ Yes, that is why I asked a specific question in construction. Everyone in construction knows what a control joint means, so there is no "source" needed for this. Plus I still gave a definition in my question for it at least enough for the purposes of the question. Contraction joint however, is a term I read only when I was reading a text about dams. The question is clear enough. $\endgroup$ – user3600630 May 9 '20 at 10:51
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    $\begingroup$ So have you considered hydrostatic loading? $\endgroup$ – Solar Mike May 9 '20 at 11:01
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They're the same thing. See the link below for an article by the Portland Cement Association. Just different vocab from different regions of the country. Another common example of this in structural engineering is mat slab versus raft slab. They're synonyms.

https://www.cement.org/learn/concrete-technology/concrete-construction/contraction-control-joints-in-concrete-flatwork

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  • $\begingroup$ Thanks, I appreciate $\endgroup$ – user3600630 May 11 '20 at 7:56

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