Pre-mixed Bucket "Mortar"??

[speed51133]

I just got into a bit of a disagreement with the guy at Floor and Decor. He is adamant that https://www.mapeihome.com/premium-mortar-for-tile-stone
is a mortar and OK to use for a backsplash behind a really hot infrared grill (16000 BTU). I stated I would be more comfortable with a portland cement based mortar than mastic. He ASSURES me this is cement based. I asked how does it stay liquid in a bucket. He stated it reacts with air and dries hard.

I did not feel like explaining the chemical reaction of cement and water vs cement and air.

I looked at the bucket, instructions, and limitations. NOWHERE does it say what it actually is. I looked up the MSDS and it is made of two types of silica and some SEPIOLITE CLAY. I looked up the stuff and "When first extracted, sepiolite is soft. However, it hardens on exposure to sun heat or when dried in a warm room". It also stated it is rather soft and can be easily scratched with a fingernail.

Wikipedia also says "In construction, sepiolite can be used in lime mortars as water reservoir.[9]
"Lime-based mortars with admixtures of metakaolin (10,20 and 30 wt.%) and fine sepiolite (5 wt.%) were prepared with the aim of facilitating their use as repair mortars in low humidity conditions. The mechanical properties and the dynamic modulus of elasticity were studied after 28,90 and 180 days of curing. With increasing amount of metakaolin in lime mortars, improved mechanical strength was observed mainly after 90 days. Addition of fine sepiolite, due to its adsorption properties for storing water for later supply to the mortar system and its microfibrous morphology,led to an improvement of compressive and flexural strength of blended air lime/air lime-metakaolin mortars,especially at later ages of curing. Incorporation of fine sepiolite into air lime-metakaolin mortars resulted in comprehensive densification of the core of the mortars. Air lime mortar containing 5% of fine sepiolite and 20% of metakaolin appears to be an optimal admixture."

SO it for sure is not portland cement. But it also is not mastic. WTF is this stuff???

[John Bridge]

I don't think you'll find that product at a wholesale tile supply. I think it's just for the retail stores. Yeah, it's mastic. Kinda like Custom's pre-mixed thinset.

[cx]

I think it rather poor and deceptive of MAPEI to label that a Mortar and not give any sort of ANSI Standard or ASTM reference for it.

I can't find any such reference in their TDS or anywhere else I looked. In their FAQ on that link you posted they make reference to "Type 1 or Premium Mortar," kinda sorta suggesting it might be an A136.1 product, but they never really say so. I've never seen the bucket up close to see what might be printed on there.

Tends to make a fella suspicious of their whole product line, which is unfortunate as we know they do make some good tile installation products.

[Tool Guy - Kg]

From your interaction, it doesn’t seem like a source outside of the store is going to help that salesperson. Mike, I don’t know if you feel like calling Christian over at the store...but maybe he can shed some light to that salesperson.

[MAPEI - Technical Service]

We would not recommend a premixed adhesive or mastic for use near a heat source. If tiling an area that is subject to high heat, a rapid-setting cement tile mortar will be the best choice like our Ultraflex LFT Rapid, or Ultraflex RS.

Premium Mortar is a product designed for the DIYer and marketed in a way that is geared toward the non-professional looking for something ready to use. It is a premixed adhesive, and not technically categorized as a mastic by ANSI A136.1 definition. Much like ready to use grouts, there are not ANSI standards for these specific types of products.

If you are ever unsure of a product and its intended use, please do not hesitate to reach out to us at 1-800-992-6273 for guidance.

[speed51133]

Thanks Holden!

Any idea what grout would be best for behind a hot stove charbroiler? Two issues, high heat and stain resistance.

[John Bridge]

Hi Holden,

It's just that we try to help our DIYers to attempt the same quality of workmanship that would be expected of a pro. Everyone knows they usually won't quite achieve that standard, but they try pretty hard. When an "expert" at a retail store gives one of our visitors a bum steer, we'll endeavor to correct it.

I certainly am not insinuating that Mapei doesn't make quality products; we all know they do, and we have promoted Mapei products for years.

But mastic is mastic.

[Dave Gobis]

Mike, cement grout properly mixed and cleaned, strike the joint rather than shape it with a sponge. That makes it dense in both aspects.

[speed51133]

Strike it as in what? How would I clean haze?

[John Bridge]

Mike,

I think Dave was confused. Sounds like he thinks you're doing masonry work instead of tile work. Cement grout gets applied with a grout float. It's then allowed to set up a bit and washed with a sponge.

[cx]

Mike, in my grout tool bucket were always some short pieces of various sizes of wood dowel rod for the purpose of striking and shaping cementitious grout joints in some applications. I think that's what Dave was referring to. Probably the same applications for which he'd use dry burlap for removing the grout haze, That would be my guess.

[Dave Gobis]

CX, your guess is correct.

[speed51133]

How about my finger? Then burlap?

[cx]

Your finger might remove and shape the grout, Mike, but it would not improve the surface density as would a hard striking tool and it's that increased density that Gobis was recommending. And if your cementitious grout is correctly mixed, I doubt your finger is gonna be very effective at doing any real striking of the joint. At least not more than about once.

The burlap works best with a bit of sawdust, but that's pretty difficult on a vertical surface, eh? The burlap alone can be pretty efficient, though.

My opinion; worth price charged.

[speed51133]

Ok. Thanks. This is a 1/16in grout joint. Looks like I'll be using a toothpick?