what type of cement or mortar


my in-laws asked me to do a small repair for an in-ground pool, top suction area.
the pool is a standard gunite diamondbrite finish and the pool cleaner goes into an opening cavity on the very top at water level, into a small round pool where the main suction line exists (another is on the bottom of pool)
in the small round area, there is a small crack in the cement right above the water line or just at the waterline
I have to drain the pool a little but am asking what type of cement to use to repair this crack as it will be exposed to the pool chemicals though most of it is above water level. none of this is the actual swimming pool, it's the small round hole outside the pool wall, about 1 foot away from the wall of the pool and exists only for the top suction line into the pool pump
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harmon wrote:

My guess is that you should use Hydraulic Cement. But someone else may have a different opinion.
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Jack writes:

Wrong guess. So-called "hydraulic" cement is just (very) quick-setting ordinary cement. Not appropriate for this type of repair.
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snipped-for-privacy@truetex.com says...

I thought "hydraulic cement" was designed to set up and cure under water.
--
Keith


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krw wrote:

I'm a little confused by the term Hydraulic cement as well
my understanding of it is:
"Hydraulic cement" is a fast setting cement formulated in such a way that it expands slightly on setting in contrast to common cement which does the opposite. As such,"hydraulic cement" is used for watertight patches of small cracks or holes in concrete.
but I don't know if Hydraulic cement can be placed in small quantities underwater. The concern would be that the water would wash away the cement or dilute the mix.
I think the main idea of Hydraulic cement is the expansive nature.
"ordinary" concretes made with portland cement can be placed & will cure underwater as long as care is taken during placement.
A tremie is used so that the concrete is "piped" down through the water & the concrete exits the tremie into the "blob" of concrete being placed. Care is taken such that new concrete always enters the "blob" so that only the concrete on the surface of the "blob" is subjected to the water / dilution effects.
The end result is quantity of placed concrete underwater where only the surface concrete has been subjected to the water / dilution effects. Typically the concrete item is enlarged to take into effect the lose of concrete quality at the surface.
cheers Bob
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Richard J Kinch wrote:

Not so. Hydraulic cement expands as it sets, sets in the presence of active water leaks, has about double the strength of ordinary cement and is waterproof. It would work just fine in the OP's situation. http://www.unitex-chemicals.com/catalog/hydraulic_cement.shtml
Your suggestion of a two part epoxy repair would work, as would polyurethane caulking. It all depends on the size of the crack and how much he cares what it looks like.
R
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RicodJour writes:

Read the MSDS of the product you cited:
http://www.unitex-chemicals.com/msds/hydraulic_cement.pdf
Where the "hydraulic" cement is shown to be ... ordinary portland cement.
Ordinary portland cement is "hydraulic", whatever that means. In civil engineering it just means "sets by addition of water". But at some point is came to mean, "meaningless term that gets suckers to pay multiples of the price for ordinary portland cement". Magic stuff to put in cracks to stop leaks. It's just ordinary portland cement with an accelerant, folks, which mixes with water and works in immersion just fine.
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Richard J Kinch wrote:

Similar makeup, different properties. I'm not sure what you mean by ordinary Portland cement as there are five different types and numerous sub-types with different compositions and properties, all called Portland cement. Hydraulic cement (and no, I don't like the name it is marketed by any more than you do) expands slightly as it sets to offset the natural shrinkage. That's the part that makes it effective in stopping leaks and plugging gaps. Another more accurate name for it is expansive cement. It is commonly used in bridge construction where cracks are verbotten. Almost all other cementitious products shrink as they cure/dry. There is no accelerant in Hydraulic...errr....expansive cement. Portland cement has additives to retard its natural rapid setting, most commonly gypsum.
R
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RicodJour writes:

The proper term "hydraulic" has nothing to do with "expansive".
http://www.fhwa.dot.gov/infrastructure/materialsgrp/cement.html
"ASTM C 150 defines portland cement as "hydraulic cement (cement that not only hardens by reacting with water but also forms a water-resistant product) ...". That is, all portland cement is hydraulic.
By blending proportions of various aluminates, silicates, and sulfates in portland cement, the shrinkage/expansion can be controlled. Shrinkage typically has everything to do with inadequate hydration while curing and not composition.
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Richard J Kinch wrote:

No argument there. We've already agreed that the hydraulic in the name Hydraulic Cement is a misnomer. Maybe I'll go to the supermarket later and buy some of that Wet Beer. ;)

Correct. By blending the component materials in Portland cement the properties can be varied as needed. Hydraulic Cement has the component materials blended so that it expands slightly as it sets. The bag of Type I Portland you buy does not expand - it shrinks slightly.
We're agreed that Portland cement comes in different types, that the properties can be tweaked by adjusting the component materials and that some cement expands more than others. Why do you feel that they're selling a bill of goods? They're already making far more money on the product because it's sold in much smaller quantities for almost the same price.
R
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RicodJour writes:

I find it hard to trust merchants who corrupt the language, especially technical language. It calls into question all technical claims.
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Richard J Kinch wrote:

Hmmm...you may have received the same rude awakening I did when they started selling New and Improved candy bars - larger package for the same size bar and they cost more. Bastids!
R
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harmon wrote:

I used an "underwater" 2 part epoxy putty for this type a repair
It came in two seperate containers (like film containers)
i don't have it any more...stuff dried up after 10 years on the shelf in the garage
Check your local pool supply
LEAKMASTER Pool Repair Putty
This convenient and versatile epoxy works underwater and cures to a bright white in 20-60 minutes. One stick format eliminates waste and misproportioning.
PP701 Pool Repair Putty - Hardens in 20-30 minutes to a fiberglass white
http://www.leaktools.com/leakmaster_repair/service.php
cheers Bob
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BobK207 writes:

That would work, but more cost and effort than a little cement.
The "underwater" claim is spurious. Any epoxy would do. Kind of like how they label bottles of ordinary aspirin as just for arthritis.
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Richard J Kinch wrote:

Richard-
Yes many epoxies will do service underwater but only some are formulated for application underwater. Usually moisture will interfere with the cure of the epoxy.
Other methods of repair will require OP to drawn down the pool level.
With true underwater epoxy OP can do the repair with water in place.
cheers Bob
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harmon writes:

What you are describing sounds like the skimmer niche.
Just use tile grout from Home Depot/Lowes. You can get a small quantity. Use sanded type if the crack is larger than 1/16", unsanded for thinner cracks. Variety of colors if you don't need just white.
See my page:
http://www.truetex.com/pool.htm
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Richard J Kinch wrote:

yeah, I read all of that (my eyes are still bleeding)
while I certainly applaud you (and the entire family) for the effort, I wonder if you could have written a cliffnotes or 'pool repair for dummies" version? the entire description on one page is exhausting and one would wish for a summary version or a simple "do this but don't do this" type of abbreviated page with appropriate links to "click here for the details"
I noted you mentioned the plaster you used (this does not apply to my simple repair..) is not longer made or available for DIY jobs, suppose I went into the plastering business, what's a homeowner to use these days?
actually, a separate page by itself for "things I have since discovered, ie. updates, tips, quick notes" would be fantastic.
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