The mission of a densifier is adding silica to the surface of concrete.  Lythic Densifier with Reactive Colloidal Silica is 99.5% pure silica, suspended by charge repulsion in an ultra-low surface tension liquid by a proprietary, “green” manufacturing process.  It increases the density of the concrete surface, making it less permeable to liquids.  It increases the surface hardness, making it withstand abrasion and take a better polish.

applied to any new or cured concrete surfaces to increase hardness and abrasion resistance, and prevent dusting

"Lythic’s nano-sized silica particles react highly effectively with lime in concrete, and bond directly to silica already in the slab. Reactive Colloidal Silica even bonds to and hardens decorative cementitious overlays that are low-lime and do not react with silicate densifiers."

Silica, Amorphous (CAS # 7631-86-9) listed on SDS

available online