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STI makes no densifier so I cannot speak as a manufacturer of this product, but in my practical experience, the answer is a strong "maybe." Generally speaking, concrete is a mixture of many natural materials in various ratios depending upon the intended use of the concrete product. For the purpose of saving time, I'll just comment about concrete used for floors that will be polished and already are in place – new or old.

These concrete products are already at a point in their lifespan where the only thing that will influence their final appearance will be mechanical and chemical treatment. STI is an expert for the mechanical portion of the work, but I'll stick to the question and advise about the chemical work.

How a Densifier Works

Densifier is used to, well obviously, make the concrete surface more "dense." It does this by growing a crystaline structure between the various natural materials in the concrete – basically like a glue to tighten the bond between large and fine aggregates of sand. By doing this, the various materials, now bonded, resist abrasion much better.

The floor doesn't really become harder per se, it becomes more tenacious. As people and equipment move across the concrete surface, after densification, it is going to wear less. The chemistry that supports this explanation also supports the statement that any concrete floor can benefit (become more dense) by applying a densifier, regardless of its starting condition.

When to Coat Once or Twice

scratch test Mohs testThe starting condition is that which determines one or two coats of densifier. Is your concrete dense or soft? Quantifying the existing density of a concrete slab is pretty easy and fast to assess with some simple tools.

For the scientific minded contractor, you'll want to buy a Mohs test kit which is available for around $100 online. For the contractor that just wants to get to an answer quickly with something from his or her tool box, a house or lock-box key will work. The test kit is nice to show an architect or consultant you are a serious about defining the concrete's condition; whereas the keys give a more general indication of concrete density.

For the sake of time, I'll offer my advice using the keys. If the key leaves a shiny streak on the surface, then one coat (two cannot hurt, but adds time and cost to the budget) will likely be enough. If the key can scratch the surface of the concrete, then it is a candidate for two coats of densifier – applied at crucial times of the polishing process.

What are "Crucial Times," you ask?

This really opens another discussion altogether that should be termed "How do I polish soft concrete?" There is much more that can be offered on this topic of "densify once or densify twice?" My advice is always to consult the people that make the product first before considering any other sources for what actions you should take.

At least by now knowing how to determine the density of the concrete, you will have confidence to proceed as expected or to stop work and get in touch with some help.


© Substrate Technology, Inc.

The above is a general guideline to determine if densifier should be applied once or twice. For any clarification of the above or to discuss your unique situation, please do not hesitate to contact STI or any of its authorized dealers for more help and advice. We are all here to supply solutions that save you time and make you money.

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