UtakataNoAnnex

Senior Member
Member Bio
Joined
Mar 5, 2020
Messages
2,779
Reaction score
3,229
The columns were wet yesterday and I could see what appeared to be cracks. I could see them from my car as I drove south so I didn't have to get too close.
I am no expert by any means of structural mechanics and engineering, but two things I can imagine are a foot here on this:

1) They are aware it's there, but are not concerned as it does not compromise the integrity of the column in question.

2) They are aware it's there and are concerned about it, but they'll take care of it before it ever comes a real issue.

...so with that, it's unlikely anything we need to be concerned about at this point. As I am pretty sure this industry that has be dealing with these issues since our civilization has leaned how to construct columns. Hope this helps! :)
 

BloorMan

New Member
Member Bio
Joined
Sep 28, 2017
Messages
70
Reaction score
716
Do you have pictures of these 'cracks'
I'm busy today but I'll try and get a better look tomorrow. The cracks, if they are cracks, may only be visible when the columns are wet. I'm sure it's nothing to be concerned with but it was an observation I made as I drove by.
 

Benito

Senior Member
Member Bio
Joined
Mar 12, 2014
Messages
6,525
Reaction score
34,882
Today.
0A6EB56C-5613-4493-B000-650838A80E33.jpeg
A2756E27-6AA4-4420-BF02-DC4DC9554B4C.jpeg
F7E02B1C-A714-435C-B90B-CECBC20DAF75.jpeg
44775CA5-F6F0-466B-B5CA-F56626EE875A.jpeg
24615870-A802-45F4-AD4B-16F7F32824E9.jpeg
289F999C-8573-4ABA-BBD5-F1B3F4C1B7C4.jpeg
B5A89ECC-B47C-4BE3-A852-5E5B414E1F87.jpeg
132A486B-2BF3-411F-9991-B965AAF71330.jpeg
EA220239-D826-4103-A6B7-1C5FF905AFEA.jpeg
 

p5connex

Active Member
Member Bio
Joined
Apr 24, 2007
Messages
991
Reaction score
216
I am not sure what you saw exactly, but it does sound a lot like craze cracks. These are noticeable when the formwork is removed as the concrete has set, but then gets wet, in this case rain/snow falling on it. Its appearance looks like dozens of hairline cracks racing around the surface of the concrete. They are superficial and mostly will have no consequence on the performance of the concrete. This can be a symptom of curing too fast, or other issues ie: water content in mixture etc. Generally, as concrete cures, the chemical processes/reactions taking place within it, drive the water inside the mixture toward the surface, where it evaporates and in many cases it drying faster than other areas, often resulting in these types of 'hairline cracks' you may have seen.

Or it could be that the building is doomed!
 

p5connex

Active Member
Member Bio
Joined
Apr 24, 2007
Messages
991
Reaction score
216
Well these are massive thick pours, meaning they generate tons of heat and evaporate water.
Yes, exactly! If you have ever poured concrete yourself, you can feel the heat the concrete emits as it cures. Not to mention, given the size of these columns, they will be curing (gaining in compressive strength) for months potentially. I recall a project where the concrete on 1 section of a slab pour, took 45 days to reach its minimum required bearing capacity.
 

interchange42

Administrator
Staff member
Member Bio
Joined
Apr 23, 2007
Messages
25,045
Reaction score
25,955
City:
Toronto
Looking at the recent photos, I am taken aback by the amount of complexity at the site.
One would think a 308 metre-tall building with no central elevator core going all the way to the foundations would be more of a walk in the park.

42
 

The Preservationist

Active Member
Member Bio
Joined
Jun 27, 2020
Messages
319
Reaction score
664
First photo a bit sub par but I've seen surface cracking or crazing at this level before. In one much more extreme case in northern Quebec during a winter pour it was so bad that they chipped the surface down, chemi bonded and patched up. I'm a Mechanical Systems design and install guy by trade so maybe someone else knows more about this.
Second photo looks like you've possibly got cracking through the entire cross section of the column. I did ask a question on this form concerning the amount of rebar versus concrete with thermal expansion of the rebar about a month ago. I suspected that quantity of rebar would cause cracking. The column will be in high compression once loaded so generally horizontal cracking shouldn't be an issue but again I'm getting a little out of my working area. Any thoughts?
 
Last edited:

Top