Has anyone tried to use a non-shrink precision grout as a mix design?  I just started making countertops and I actually tried using the Pak-Mix brand.  It seems to work pretty well but it sets up pretty quickly (20 min).  I used it because it has a really small aggregate similar to a sand mix but is a lot stronger.  Out of the bag both Quickcrete and Pak-Mix claim significant psi advantages over any box-store bought premix I have seen.  At a flowable consistancy, they claim 5000 psi after 1 day, 9000 psi after 3 days, 10,500 after 7 days and 12,000 after 28 days.  This is with water only.  With a superplastisizer and less water, as well as fiber and steel reinforcement, this seems like some pretty strong stuff.  The addition of heat curing would also make it stronger. I found that it takes acid stain a lot better than regular concrete.  A 50/50 mix (malay tan-kemico) applied after 4 days turned it a solid dark tan.  Do you think that may mean that it is more susceptible to unwanted stains as well?  I didn't use any admixture products in the mix.  It also absorbs integral color well.

Several issues I found with this product is that it tends to produce quite a few air bubbles over a longer span than normal concrete while setting up, requiring more slurry when polishing  Also, I found that if it is not wet cured enough, it curls a lot. 

 

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When I say heat curing will make it stronger, I just mean quicker, not really stronger
It's hard to say whether air bubbles and curling is specific to the product or if it's related to your mixing process and lack of admixtures in your test. I think you will always find a less mottled look with polished vs unpolished or varried polish. I know Dave McVey has been playing with Polyblend Sanded Grout for GFRC. Do a search for Polyblend Sanded and see some of the thoughts on that. I would guess that non-shrink percision grout is basically regular sand/cement with some CSA cement and shrinkage additives. The problem with most pre-batched mixes is you can't really find out what's in them, which makes figuring out additive dosages a guessing game.
You have to be careful what you add to it in an attempt to make it better. For instance it may already have a powdered plasticizer that may be incompatible with the one you intend to add.

By the time you manipulated it to do what you want you might as well make your own.

Mark C

Ok, good point. 
Mark Celebuski said:
You have to be careful what you add to it in an attempt to make it better. For instance it may already have a powdered plasticizer that may be incompatible with the one you intend to add.

By the time you manipulated it to do what you want you might as well make your own.

Mark C

Tim,  Mark is right.  Just make your own, then you know what is in it.  As most know, I like Rapidset.  My brother developed a mix that is really easy to do, and fairly consistent.  Definitely easier then remaking someone else's mix to be yours.

 

There are many great mixes on this site.  Too many people in this industry are trying to reinvent the wheel.  The mixes are easy.  Pick the mix you like, and then concentrate on selling your product.  then, when your making money, you can spend time playing with new mixes.


OK, that sounds like great advice.  When I was trying my first countertop, it was hard to find a good mix so I just went with something that was strong and premixed.  I read Cheng's "Countertops made simple" but there was only one mix design given and no specs on it (Strength, time, etc)  and there was not much online I could find with exact mixes so I decided on a premix.  Now that I have done a few, I realize that the book is much too simple and I can definitely learn a lot more from the pro's on this site.  Thanks.
Tommy T Cook, AKA The Gnome said:

Tim,  Mark is right.  Just make your own, then you know what is in it.  As most know, I like Rapidset.  My brother developed a mix that is really easy to do, and fairly consistent.  Definitely easier then remaking someone else's mix to be yours.

 

There are many great mixes on this site.  Too many people in this industry are trying to reinvent the wheel.  The mixes are easy.  Pick the mix you like, and then concentrate on selling your product.  then, when your making money, you can spend time playing with new mixes.

The non shrink grout and Polyblend sanded grout are two completely different birds.

 

I have used Quickrete nsg on a counter as well as a sink. It works but I would be afraid to use it on a large top because it really does shrink and has a really high binder content. Setting time and the dark color were also an issue. It likes to mix wet and segregate. The compressive strengths are through the roof but I suspect this comes with a trade off for flexural strengths. I consider the nsg more of an ecc minus the fiber. PVA may ad quite well and boost the flex strengths but I don't know what that does to help the color.

One of the already included admixtures in grout of this type - machine grout - is an air package. An air inducing additive which creates air in the mix and acts as a fluidifier.

Whatever mixing process you use will not ever eliminate air bubbles in this mix. It will always create air bubbles and you will always have to slurry more than most other mixes.

 

They will always have a tendency to curl more as they are so cement rich and rarely contain pozzolans that would reduce cement load and reduce proclivity to curl.

 

The aggregate gradation in these grouts is usually designed for FLOW so if you could buy it without the air package added and some pozzolan in place of a portion of cement  Then you may think about using it. But at that point why not just buy  that agg. blend and make your own? 

Yeah, I'm just going to make my own concrete mix and avoid using the grout.  Thanks to all who contributed and helped me with this decision.

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