hydraulic cement --- expansive cement --- cracking?


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?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Matt wrote:

Why would you consider using expansive cement? I'd be more worried about cracking the pipe. Why not caulk?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I'd use expansive foam out of a can instead.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 09/17/2010 07:03 AM, snipped-for-privacy@earthlink.net wrote:

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Matt wrote:

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Sigh. Why don't you post some questions? At least I'd know yours would be sensible.
R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 09/16/2010 09:04 PM, Matt wrote:

Please see: http://www.quikrete.com/productlines/HydraulicWaterStopCementPro.asp If you look at the data sheet you find that a two-inch cube expands to cause a compression of 5500 psi. The tensile strengths of concretes are on the order of 500 psi, thus the concern that expansion near the edge of the slab could crack off a piece.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 09/17/2010 10:11 PM, RicodJour wrote:

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:
http://inderscience.metapress.com/app/home/contribution.asp?referrer=parent&backto=issue,2,6 ;journal,2,5;linkingpublicationresults,1:121239,1 (((((

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.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 18 Sep 2010 09:02:19 -0700 (PDT), RicodJour

You said enough right there.
--Vic
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 09/18/2010 11:02 AM, RicodJour wrote:

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 09/16/2010 09:04 PM, Matt wrote:

The following indicates that the expansive cement may cause cracking.
http://inderscience.metapress.com/app/home/contribution.asp?referrer=parent&backto=issue,2,6 ;journal,2,5;linkingpublicationresults,1:121239,1 ((((( Abstract: Expansive cement is powdery material which produces expansive stresses 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. )))))
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:
http://wiredspace.wits.ac.za/bitstream/handle/10539/3899/MJ%20LITTLE%20MScEng%202006.pdf?sequence=1

http://www.rocscience.com/hoek/pdf/3_Rock_mass_classification.pdf
http://www.engineeringtoolbox.com/concrete-properties-d_1223.html
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

to do with it. <<<<<<<
That's because you don't know a whole lot about concrete.

No, if I had meant tensile strength, I would have written tensile strength.

Yup..... its called engineering but in this case "precise" would be a stretch.
You're treating this whole thing in a WAY too theoretical manner. If oyu want to study this to death read Park & Paulay's Reinforced Concrete. & take a look at at http://www.scribd.com/doc/37892576/Anchoring-in-Cracked-Concrete
If you want an answer; post a photo & provide some more precise dimensions.
Depending on the geometry of your situation, with a photo including a tape measure, the experienced contributors on AHR could probably tell in an instant whether there is any danger of the slab cracking.
hint: your answer doesn't involve the behavior of norite in the laboratory
I don't understand your approach to this at all.
cheers Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

So you think...... That's why SOME numbers that describe the geometry (& a photo) would be helpful.
I think Rico was correct, this has to have been a troll post. Otherwise why so much effort to argue and so little effort to provide use information?
Good luck with your slab.
cheers Bob
PS when I tell someone with no real word experience "I don't think that will work" and they reply with "How do you know? Show me the evidence. Show me some calculations"
I respond..... "Sometimes 35 years of engineering experience gives me the correct answer without calcs."
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.