Expansion Joint Crack Cause/Remediation

[ChalMel13]

Hi all,

I was inspecting a bund wall and I found 3 cracks on the expansion joints (see pics). The bund has concrete floor and walls and is just 10 yrs old. The drawings indicate that expansion joints has metal waterstop but in two occasions where sealant is coming off I can't see it. In 30% of the joints I can see the waterstop on the top of the wall but in the rest it is not apparent if they have been installed.

All three cracks are on the outside of the wall. One of the joint cracks is located on the Diamond Floor Joint (Construction Joint) where the other two are where the intermediate bund wall connect to the main wall. Operators reported that sealant is leaking on those joints

Could those crack been due to incorrect construction or due to shrinkage?

 

[bones206]

It certainly looks like shrinkage cracks to me. Perhaps they overlooked the dowel cap since it wasn't drawn in the detail.

Another possibility is that the center rib of the waterstop was not installed in a wide gap as shown in the detail, so it wasn't able to flatten out and allow expansion without causing restraint at the joint. The gap was not specified in the detail, so it could have easily been overlooked.

 

[Just Some Nerd]

Not familiar enough to claim it's related to this cracking but specifying square dowel caps for a round bar seems a bit odd? Typically I also see it specified that the capped end is greased. The cracks all appear on the left side of the joint either by complete chance (1 in 4, so within the realm of just bad odds and it's related to the waterstop as pointed out above) or because they've installed the dowel caps on the same side each time.



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Why yes, I do in fact have no idea what I'm talking about

 

[MotorCity]

Maybe its the light in the photos or some really bad concrete, but the wall looks much older than 10 hours (in the first photo it looks like there's pavement up to the wall with weeds around it). Given the color variation on each side of the crack, it almost looks like a patch job. Since the crack does not appear to go all the way through the wall, I doubt its due to shrinkage. It looks to be a near surface crack that could have been caused due to careless stripping of the formwork or a lack of form oil. For what its worth, I'd have concerns about this joint functioning as an expansion joint. The measures that have been taken to accommodate expansion will be negated by the fact that there is reinforcement across the joint which will restrain movement

 

[ScratchyFilm]

Maybe I am really bad at google searching... Can someone explain the purpose of a dowel cap to me?

 

[Enable]

ScratchyFilm: the idea is that you want something to keep both sides in the same plane but also don't want whatever it is you put in their to prohibit the nature of the joint (namely the thermal movement). The dowel itself keeps the parts plane and the cap reduces bond to the concrete, which allows the joint to move.

Often you'll see them cast one end and greased at the other. But it's not uncommon that the very tip of the bar doesn't get greased (easy to miss), which is why engineers spec the caps; hard to miss if there is a big plastic thingy or not at the end!

Very hard to say what this is from as it could be a lot of things. Can I ask why we care though? I assume the 10hrs is a typo and you meant 10 years. Honestly there is nothing to do but to rub the wall if the owner wants (repair caulking as well and extend to cracked area - may use a crystalline waterproofing / grout if feeling fancy), and wait until the wall needs to be replaced. Any invasive repair attempt at a joint like this is likely to cause more leak problems then it solves. So I'd Band-Aid it to extend the service life, and wait until the wall needs full replacement prior to doing anything substantial.

 

[CovertShear]

@MotorCity

Given the color variation on each side of the crack, it almost looks like a patch job.

I also thought it could be a patch job.

 

[ScratchyFilm]

That makes sense. This reminds me of seeing this DOT detail on one of my first jobs and questioning why they would grease opposite sides instead of keeping the greased side the same for thermal expansion.

 

[JoelTXCive]

@Scratchy - Google "speed dowels" and look at the images.

They are plastic sleeves that fit over the rebar end and allow the rebar to move.

The old-school way of doing it was greasing one end of a smooth dowel and wrapping the dowel in a cloth.

 

[wrantler]

Is there no vertical bar in the wall? Is it just floating on the slab?

My best guess is something is trying to move laterally and the galv bars are restraining it. Causing the spall. I would not put a bar here, to me this is poor detailing.

 

[ChalMel13]

Everyone,

Thanks for your input and apologies for the delay.

I assume the 10hrs is a typo and you meant 10 years

You are right. My apologies for the confusion.

Another possibility is that the center rib of the waterstop was not installed in a wide gap as shown in the detail, so it wasn't able to flatten out and allow expansion without causing restraint at the joint

Could you pls elaborate that as I’m not familiar with the process?

Any invasive repair attempt at a joint like this is likely to cause more leak problems then it solves.

Why do you think that? If in fact the joints were constructed incorrectly (caps, joint width, no water stop) wouldn’t mean that the structural integrity of the wall is compromised?

Is there no vertical bar in the wall? Is it just floating on the slab?

Could you pls explain? Not sure what you mean. See below the relevant drawing

 

[HTURKAK]

Both of them ... ( incorrect construction+ shrinkage ) and single reinf. and probably temperature effect..


The last picture ( Section A) implies the height is around 1.5 m .

- Min. wall reinf. should be provided at the front face,
- the wall should be poured in staggered way,
- the dowel SHALL had sleeve and cap at one side to provide free expansion ..,

Pls look to the pages of the following doc. 11&12 for round dowels and square dowels

https://reids.co.nz/upload/modules/..._Danley_Product_Catalogue_2021_ANZ_DPS_LR.pdf

Tim was so learned that he could name a
horse in nine languages: so ignorant that he bought a cow to ride on.
(BENJAMIN FRANKLIN )

 

[Just Some Nerd]

That section makes it apparent why it only cracked on the outside...the steel is as far from that face as it can be

Seems like a poor designer to me...single reinforcement but not central, specifying a square cap for a round bar, vertical bars not shown at all on that plan detail, etc. all seem pretty sloppy.

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Why yes, I do in fact have no idea what I'm talking about

 

[Settingsun]

My speculation is dowels not installed correctly so not releasing restraint as intended and causing concentrated forces, and/or everything going on at the joint resulting in the builder not wanting to compact the concrete properly there.

If in fact the joints were constructed incorrectly (caps, joint width, no water stop) wouldn’t mean that the structural integrity of the wall is compromised?

It will work structurally as long as the dowels are there. The issues could be loss of retention and loss of durability. Does it still retain whatever it's meant to? Does the environment promote corrosion or is it benign?


Just Some Nerd, I wouldn't say there are any major transgressions. The longitudinal reinforcement is only 20mm off central, square dowel sleeves can go on a round bar as their purpose is to allow movement and this still works, and the reinforcement isn't tagged on the joint detail so the builder has to look elsewhere and will see the vertical reinforcement.

 

[bones206]

Could you pls elaborate that as I’m not familiar with the process?

I’ve never used stainless steel waterstops, but it seems like the center rib is designed to flatten out during expansion. Without that rib, the water stop material would strain when the wall is shrinking. In my mind that flattening mechanism only works if the center rib is in an air gap/ joint. I may be missing something but I can’t see that working well if the center rib is fully encased in concrete.

This detail appears to show a wide joint, which makes sense. But I looked up the manufacturer’s cut sheet and they show the center rib fully encased in concrete.

https://www.jpspecialties.com/SS_Waterstop_Subpack.pdf

 

[bones206]

In the third photo, is the slab also cracking at the joint location?

 

[ChalMel13]

Does it still retain whatever it's meant to? Does the environment promote corrosion or is it benign?

It does retaining water but some joints leaking at the base. Humidity is high there so I guess promotes corrosion.

In the third photo, is the slab also cracking at the joint location?

The slab is cracked in the location. See below. The crack on the 1st pic is leading to the slab joint on the 2nd pic

 

[bones206]

It kind of looks like the slab is cracking halfway between restraints: tank on the left and a catch basin on the right.