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Unread 06-15-2020, 05:16 PM   #3
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

Join Date: Jul 2004
Location: Nashua, NH
Posts: 14,280
Cement cures regardless of whether it is kept wet of not! There are things that can be mixed with cement to slow that chemical reaction down. Take something like hydraulic cement...made of the same stuff, but has no inhibitors in it...gets hard in minutes. A typical thinset may have a usable pot life close to 2-hours, depending on temperature and type.

Cement literally grows crystalline structures as it cures. Those are relatively fragile. IF the modifiers that are coating them needs to dry to be able to perform their job, they could either be washed away if used too soon, or not provide the support for those crystalline spikes. Once those spikes are broken, they don't grow back as they become inert as they chemically change.

So, yes, there are different modifiers. They also get used in different quantities in the recipe selected by the manufacturer along with how consistent the particles of cement are, and the type and volume of aggregates (nominally sand) selected and other things that may help in storage or spreadability, etc.. That's why there are so many different brands and types within a company's selection.

Many of the modifiers sold in products today get stable while still wet as the cement cures. The hassle is, the ANSI standards used to classify them don't necessarily give the uninformed user any clue as to which ones will work in this situation or not. Historical experience is usually good, but beware of following old recommendations especially if the product says new, improved...something obviously changed, and it may no longer work well.

If the manufacturer says they'll work, you've got some assurance that it's a viable product for that application.
Jim DeBruycker
Not a pro, multiple Schluter Workshops (Schluterville and 2013 and 2014 at Schluter Headquarters), Mapei Training 2014, Laticrete Workshop 2014, Custom Building Products Workshop 2015, and Longtime Forum Participant.
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