[cluelesswonderer]

Hello! I have absolutely no background in the sciences / chemistry, so I thought maybe you folks could help dumb it down for me. I am renovating an old house and just got new concrete poured in the basement. I want to polish the floors and leave them uncovered for environmental and health purposes. I don’t want any vinyl or other unnecessary finishes.

The contractor who does the diamond polishing says he needs to add a densifier, which is a lithium silicate nano particle based product.

The manufacturer indicates that the product once cured has the PH level of 11-12 and is highly anti bacterial naturally because of this. Here are the exact words from one of their literature materials:

“The technology used to make “said product” makes it alkaline by nature. The typical pH of our 100% mineral coating is 11.5 to 12.
 
Even when it is applied on the floor for long-time, the pH of the dried surface will remain high. Once it is on contact with water or humidity it will produce OH- ions. These in turn will affect the growth of any microorganism preventing on the floor surface.
One of the direct consequences of that is the odor control property of “said product”. It can also reduce chances of cross contamination in areas like clinics, Hospitals, Schools and airports.

Since the “said product” coating is 100% mineral and has a crystalline structure. When cured, the molecular arrangement of billions of pointy crystals forms a micro sand paper like surface (fig.-1). These formed clear and transparent crystals reflect 100% of the light generating shine to the floor without absorbency.“

I have two concerns which I am hoping a chemist can address:
1. Does the fact that this product contains nano particle lithium silicate create any health issues after the product has cured? For example, walking on the flooring, a baby crawling on it in the long term, any dust particles arising from the polished concrete floor, etc (inhalation / skin contact)?

2. What does it mean when the company indicates the PH level is 11-12? What does this mean for residential safety of occupants who spend many hours at home and on or near the finished floor that contains this product, albeit cured? Are there any health concerns here due to the chemical nature?

Thanks everyone. Really hoping to get some insight. I can share the product name and SDS I just don’t know if that’s permitted here.

[Sideshow]

The product probably contains a solution of lithium silicate, but given the current price of lithium (thank-you new battery technology) it's more likely to be a blend of lithium, potassium +/or sodium silicates. It may also contain some potassium methyl siloxinate (about 2 - 3%) if it's a better class of product (this acts as a hydrophobing / soil rejection agent on cure).

As to "nano" ... na no no no .. this will be a solution and should be significantly "sub-nano", unless they have played around with silicate pH significantly - and saying it has a pH of 11 would suggest otherwise.

Densifiers like this work by forming complex calcium metallo silicates, which close the pores in concrete. As they are alkaline, and most reactive concrete also has some free alkalinity before it's fully cured (and some even well after that) the surface may have some alkalinity, but once cured that alkalinity level falls away and the complex calcium metallo silicates aren't soluble enough to contribute significant active pH.
Also, it would be normal to densify after polishing (or at least after the first rough polish) as most densifiers are "case hardeners" (i.e. they only operate in the top few mm of the concrete surface) so applying them and then polishing them off seems counter productive and wasteful of both the densifier and harder on the polishing process.

The crystal formation that you talk of SHOULD be the formation of the complex calcium metallo silicates, which will "glass" the concrete - as for the "pointy" bits - ask them for a SEM photo showing the claim to be accurate and a surface wipe test for the anti-microbial claim. I suspect you'll be waiting a long time.

[Borek]

Does the fact that this product contains nano particle lithium silicate create any health issues after the product has cured?

Should not. Small sizes of the particles helps them get into even the smallest cracks, but curing means bonding, so they become part of the final solid.

What does it mean when the company indicates the PH level is 11-12?

Not much. pH is not property of the solid, it is property of the water solution. They probably use some (elaborate) procedure to mix the product (in specific amounts) with the water (in some specifically defined conditions) and measure pH (sticking the electrode into the slurry) afterwards. In practice after the curing water in contact with the surface won't change the pH almost at all, as any pH change requires dissolving part of the material, and dissolving would mean the surface is soluble and it won't stay polished for long (which is exactly the opposite of what is the additive purpose).

[cluelesswonderer]

Does the fact that this product contains nano particle lithium silicate create any health issues after the product has cured?

Should not. Small sizes of the particles helps them get into even the smallest cracks, but curing means bonding, so they become part of the final solid.

What does it mean when the company indicates the PH level is 11-12?

Not much. pH is not property of the solid, it is property of the water solution. They probably use some (elaborate) procedure to mix the product (in specific amounts) with the water (in some specifically defined conditions) and measure pH (sticking the electrode into the slurry) afterwards. In practice after the curing water in contact with the surface won't change the pH almost at all, as any pH change requires dissolving part of the material, and dissolving would mean the surface is soluble and it won't stay polished for long (which is exactly the opposite of what is the additive purpose).

I appreciate the answer, albeit it’s a bit complex for me. As I mentioned, I have no science background. Basically, I’m just wanting to make sure this is a safe product and method to be used in a residential basement long term. I have a toddler who will be spending time there and intend on making it a play space. Hence, my concern about materials. Do I have anything to worry about from that perspective?

[cluelesswonderer]

The contractor also says that a sealer can be applied, but I am not at all familiar with the composition and whether it is a safe and non toxic option? It contains these “ingredients.”

N-(3-(trimethoxysilyl)propyl)ethylenediamine
Alcohols, C14-15, ethoxylated .Alpha.-Tridecyl-.Omega.-Hydroxy-, Phosphate, Ammonium Salt

[Borek]

Do I have anything to worry about from that perspective?

I strongly doubt.

Although I am not convinced bare, uncovered concrete (polished or not) is something I would like to play on. Hard and cold.

[cluelesswonderer]

Do I have anything to worry about from that perspective?

I strongly doubt.

Although I am not convinced bare, uncovered concrete (polished or not) is something I would like to play on. Hard and cold.

That was definitely a thought. There will be rugs and appropriate material for the children to play on. And the floor has heating! Not sure if that affects anything. But yes, in floor heating. I haven’t taken this process lightly, hence I’m inquiring so much in depth information, to make sure safety is top priority for my family

Also, what are your thoughts on the sealer I noted above? Worthwhile or avoid based on composition/ingredients?