Sodium silicates and sodium silicinates are both large and difficult to get into the slab. All of the chemical hardeners benefit from the use of surfactants. Wetting agents make things wetter thus allowing them more dwell time and may allow them better penetration into the slab. Mechanical scrubbing is effective in aiding penetration of these two types of chemical hardeners into the concrete. A lower concentration may also benefit these types of hardeners in trying to get them into the concrete.
It may be beneficial in aiding penetration of chemical hardeners to apply them in the afternoons when temperatures begin to fall and concrete is at its lowest relative humidity and relative humidity in the air is climbing.
The final piece of application is coverage rates. In order to be effective chemical densifiers have to be used to rejection. When the slab cannot take any more material it is full. If it still has the capacity to accept more chemical hardener then it has not reached saturation or its full potential. If they are applied at coverage rates in excess of the recommended application they have little long-term affect on the slab. All of these products get into the concrete due to capillary actions. The longer they stay on the slab the more product you can get into the concrete. If you increase the coverage rate you decrease the dwell time. This results in more product sitting on the surface and achieving less penetration into the slab.
Even though we do not completely understand how they work, we do know that when chemical hardeners are applied correctly they can improve the performance of a concrete slab. They will not make bad concrete good, but they can make good concrete better.
Mark Wetherell is with Global Polishing Systems. He has been working with industrial densifiers for 15 years. You can contact him at firstname.lastname@example.org.