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zel
07-29-2001, 01:31 PM
Does thinset have a shelf life?

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Rob Z
07-29-2001, 02:14 PM
Hi Zel

Yes...and no.

When my wife's uncle was at the Portland Cement Association, they conducted experiments where they stored portland cement for many years, decades even, and then made products from the cement. He said for properly stored samples, there was no appreciable difference from the new and old materials.

With that being said, thinset at a store like HD may have been sitting on the shelf for years, with it being returned who knows how many times. or left on the concrete floor, or left in the back of someone's truck, or out in the sun, or who knows what. Even at the tile supply stores, all products aren't rotated. And not all maufacturer's make the same quality bags.

So, to be safe, get fresh stuff. If you get your materials at HD, grab it off the pallet of material as they are pulling off the shrink wrap to load it on the shelf. Avoid that pile of material that looks covered in dirt and pushed way to the back.

Rob

zel
07-29-2001, 02:20 PM
Ummmm, like the bags that have been in my basement for a couple years? They are regular thinset, and I am going to take them back and get modified.

John Bridge
07-29-2001, 02:26 PM
The bags in your basement might have turned into boat anchors by now.

[Edited by John Bridge on 07-30-2001 at 05:48 PM]

Bud Cline
07-29-2001, 10:10 PM
I am convinced thinset does have a shelf life.

Lumber yards here store thinset in outdoor sheds, though sheltered from the elements directly, I think humidity can have an affect.

These products don't always get rotated you know and can sit around for too long. If a bag has rocks in it that are slow to absorb water and break down during mixing, then I'd say the bag is spoiled.

chip
07-30-2001, 06:05 AM
The shelf life issue is a good question.

The problem is as someone mentioned, the bags and their liners.

Even the best liners can and will allow moisture vapor in, and when it contacts with the cement in the mix, the chemical reaction takes place. Once that has happened you will never have the opportunity for that area to be reused to form good hard mortar.

Once cement hardens, it has done it's job and isn't going to do it again.

Art

Uri
07-30-2001, 09:17 AM
Both, Flatile and Rob is right. Portland cement has a shelf life only because of its contact with humidity. The chemical reactions of hardening are irreversible. If is not stored in very special conditions, will have a shelf life, regardless of the packaging quality. Good quality bags with good linings, will increase the shelf life but will be still there. Bud said about rocks... Rocks in cement bags are due to moisture. If you would take out only these rocks from the bag, mill them and try their hardening, you would realise that this material will harden very slowly or not at all. Even hardened, will be week, so rocks in the bag, are diminishing the quality of all the rest powdery staff which would be still good.
Best regards,
Uri

zel
07-30-2001, 10:25 AM
Well, the bags may be bad. The question that remains is the ethical one. Should I take the $50 hit or schlep them back to Lowe's for a store credit. Life is full of difficult decisions. I don't care about the store, I just don't want some poor sap like me to get burned. I'll probably accept it as punishment for failing to get this done.

chip
07-30-2001, 12:13 PM
The latter would be the proper decision, and thank you for the opportunity to touch on this subject.

Uri,

Thank you for putting it so eloquently, as you realized I was not quite capable of making the point.

Art

zel
07-31-2001, 11:55 AM
What about grout? I picked up one of the bags of grout the other night and it seemed pretty loose. When I get to the grouting stage, should I just look for lumps and remove them or is there something different going on with grout?

kalford
07-31-2001, 12:04 PM
Same rules apply to grout too Zel.It is also portland cement based just like the thinset

zel
07-31-2001, 12:29 PM
I hate to be hard-headed and dense--just like the bags of thinset--but did Uri mean that you could get rid of the rocks? I'm really mostly concerned about saving the grout at this point.

kalford
07-31-2001, 09:28 PM
Yes.The rocks are just cement that has done what it was designed to do and is now useless.The rest hasn't undergone the chemical reaction and is still useful.

chip
08-01-2001, 03:59 AM
The rocks are cement and sand that happened to be in the area.

What proportion cement? Sand?

Who Knows?

Why take a chance?

Art

Rob Z
08-01-2001, 06:47 AM
Hi Zel

Who knows if the rest of the ingrediants in the bag are still fresh? As Art said, if the proprtions are right?

As cheap as grout is, and as much work as you've put into the installation at that point, you'll be hating life if there is a problem with the grout.

I'd get new stuff and not take the chance.

Rob

Uri
08-01-2001, 11:04 AM
Hi Zel,
Generally talking, the guys are right about the lumps and chances but with the grout is slightly different. Grout even is still a sand cement mixture (mainly), the cement ratio is much smaller. Supousingly, all bags were mixt homogenious to start with, so, in a formed lump will be a relatively low amount of cement. As well, grade of finish of the chemical reactions. Reactions are developing quite slowly and the grade of getting to be finished depends on the time factor and quantity of moisture. My suggestion would be to try to broke the lumps in your fist without using any tool. If it brakes, brake all what you can and you may put it in your mixture and use it. Whatever lumps are not braking, take them out. If the bag is mostly full of lumps, go for the fresh staff. Take into consideration that even the very fresh staff will have soft lumps.
Best regards,
Uri

John Bridge
08-01-2001, 02:22 PM
Jeopardize a job for the sake of a lousy sack of cement? Throw it away, and buy new stuff.

zel
08-01-2001, 02:48 PM
Thanks, everybody. I'll take all of this under advisement.