All things in polished concrete relate to physics and chemistry. With that in mind, let’s look at how moisture interacts with concrete and polishing chemicals, with an additional focus on efflorescence.
Moisture in concrete can be measured as a moisture vapor emission rate, or MVER, and as in situ relative humidity, or RH. Just as concrete density and porosity affect the absorption of densifier and colorants, the porosity of a slab will also affect MVER and RH readings. The moisture level in turn can affect the vibrancy and staying power of topical color, the penetration of densifier, the clarity of shine, the strength development of concrete, and the appearance (differential cure marks) and level of efflorescence.
Topically applied dyes penetrate the concrete surface but do not chemically bond to reactive elements in the concrete. Many of you have experienced topical-color shifts of intensity on some jobs. The reason is often related to barometric pressure and vapor drive changes that occur when acclimatizing the building.