When using an expansive ("hydraulic") cement, is it possible that the expansion could cause cracking in the existing structure due to too much expansion?
I have a pipe with an OD of about 4" going through a 6" hole in a concrete slab, so there is a 1" gap around the pipe.
The edge of the hole is just a couple inches from the wall, meaning that the hole is close to the edge of the slab.
If I fill the gap with an expansive cement, do I risk cracking the slab?
Why would you consider using expansive cement? I'd be more worried about cracking the pipe. Why not caulk?
I'd use expansive foam out of a can instead.
In a basement floor the water table outside could be above the floor and water could spring up around the pipe. Cement that shrinks upon curing (ordinary portland cement) could let water in between the concrete and the pipe.
Could...but you're asking about your situation, not a theoretical, right? More info is necessary. What are you trying to do exactly - just plug the gap? Is there a known water situation? Etc.
The hydraulic cement would not be a problem, and it doesn't necessarily have to be the full depth of the slab. Whether it is the right material, and approach, to use, would depend on other factors.
R
Please see:
You are reading that wrong. The 5500 PSI is the compressive strength of the hydraulic cement. Typically cement has a compressive strength of around 3000 PSI, so they're saying, "This stuff is strong!"
That is totally different than how much force the "expanding" cement exerts as it "expands". There's no apparent cause for alarm that what you are contemplating - though you still haven't given details - will cause a problem. The same cannot be said for the reading comprehension skills... ;)
R
see:
Oh yes, I see you're right. So you have shown that I misinterpreted a number on the data sheet.
You have not shown that there is no expansion that could cause the existing concrete to be broken apart. Note the following as an indication that you may be wrong that way:
chemical reaction. This paper examines possible breakage of hard rock under confining loads using expansive cement. Laboratory tests are conducted to assess the maximum expansive pressure produced by expansive cement. This is then used on norite rock samples under load-free and uniaxial loading conditions, to examine crack formation and the time taken for crack development. Test results show that expansive cement is capable of breaking norite rock under uniaxial loading condition. Further testing is required to determine its ability to fracture rock under other loading conditions. )))))
Then treat it hypothetically with what I've described so far.
during chemical reaction. This paper examines possible breakage of hard roc= k under confining loads using expansive cement. Laboratory tests are conduc= ted to assess the maximum expansive pressure produced by expansive cement. = This is then used on norite rock samples under load-free and uniaxial loadi= ng conditions, to examine crack formation and the time taken for crack deve= lopment. Test results show that expansive cement is capable of breaking nor= ite rock under uniaxial loading condition. Further testing is required to d= etermine its ability to fracture rock under other loading conditions.
No.
I didn't realize I was responding to a troll post. That's what it is, right? The typical troll post structure - ask a question, make some mistakes in the post, then argue when it's pointed out that you're a twit and continue to make mistakes to keep things moving along. On the very slim chance that you're not a troll, and just an uniformed twit, I'll give you some homework to at least help with the uniformed part.
- Look up the definition of 'confined', and then compare that to your pipe in hole situation.
- Look up norite and determine just how far removed concrete is from norite, and how far norite rock is from your house.
- Re-read the last sentence of your quoted part, and see if you can parse that into something that you understand and how it is applicable to your situation. Feel free to ask a high school kid for help if you get stuck.
R
You said enough right there.
--Vic
see:
during chemical reaction. This paper examines possible breakage of hard rock under confining loads using expansive cement. Laboratory tests are conducted to assess the maximum expansive pressure produced by expansive cement. This is then used on norite rock samples under load-free and uniaxial loading conditions, to examine crack formation and the time taken for crack development. Test results show that expansive cement is capable of breaking norite rock under uniaxial loading condition. Further testing is required to determine its ability to fracture rock under other loading conditions.
Okay, and if the style or content or lack of content of my posts upsets you or is unpleasant to you in any way, you please feel free to stay out of the rest of the thread.
I see on this thread approximately _zero_ support for your claim that it is impossible for the slab to crack.
I see nothing indicating that you have any special knowledge or understanding of the situation I have described.
So yes ... please feel free to put me in your killfile.
The following indicates that the expansive cement may cause cracking.
Somebody please correct me if I am wrong, as I don't have special knowledge of materials science, civil engineering, ceramic engineering, or practice with concrete.
As I read the abstract, a column of expansive cement was used to compress a column of norite in one dimension and crack it.
I find that norite rock has a compressive strength something like 34-85 times the tensile strength of concrete and a tensile strength 2-6 times the tensile strength of concrete. Norite's compressive strength is about
4-6 times that of concrete:Therefore I am inclined to suppose that concrete would crack whenever norite would crack.
Further I am inclined to suppose that it is say 50 times easier (cf.
34-85) to crack concrete by stretching than to crack norite by compression, meaning that a far smaller thickness could crack concrete by stretching than would be needed to crack norite by compression.Unfortunately the abstract doesn't quantify the result,
It seems obvious that a thin-enough concrete pipe of big-enough diameter filled with expansive cement would crack, the radial expansive force translating to a stretching and cracking of the pipe along its circumference.
So in my OP, I find it hard to believe there is no combination of hole diameter, pipe diameter, and distance from the wall that would cause cracking in the slab. The question would seem to be whether the particular combination I have described in my OP presents a cracking hazard.
And the pipe would be the only leak point? That's a dream. I'd use caulk and backer rod and be done with it.
Sigh. Why don't you post some questions? At least I'd know yours would be sensible.
R
ipe diameter and distance from the wall that would cause cracking in the sl= ab. of course, there is a combination (probably more than one) that would
to do with it.
pipe diameter and distance from the wall that would cause cracking in the = slab. > of course, there is a combination (probably more than one) that would
And it allows you to identify wrong answers and approaches quickly.
But of course nowadays, with the Googler and the Intertubes, anyone can browse around a bit, graze on information they have no ability to digest, and come up to speed without having to waste all of those years getting that thing called 'experience'.
R
The answer to your question should have been YES. What did you end up doing?
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