Hydration produces calcium-silicate-hydrates (CSH) crystals that make concrete hard. Excess water in the mix eventually evaporates, leaving behind tiny pores where the water previously took up space.
A by-product of this reaction is calcium hydroxide (Ca[Oh]2), also known as lime. Lime adds no structural value to concrete. Lime born by water can move through the slab and become efflorescence. It is the “dusting” that occurs on concrete that has not been densified.
Densification is the process of permanently closing pores in the top layer of the slab. Silica added to concrete surface reacts with available calcium hydroxide and produce additional CSH crystals that permanently bond to existing CSH, filling the microscopic pores. The surface is less porous, denser and harder. One of the original uses of densifying was to eliminate “dusting” by tying up lime.
The biggest difference is the method by which silica is delivered to the calcium hydroxide. Originally, alkali-metal compounds called “silicates” were used: sodium, potassium, and more recently, lithium-silicate. This older technology works but has many drawbacks for contractor and owner:
- high pH levels of working materials (most greater than pH 11)
- high alkaline surface residues
- potential for whiting on the surface that is difficult to remove
- high viscosity requiring time-consuming scrubbing to achieve penetration
- labor-intensive application and rinsing
- extensive delays for dwell times and drying times
- disposal of hazardous slurries creates environmental issues on the job site
OmniSil Densifier is colloidal silica, not a silicate. It is refined nano-particles of highly pure silica suspended in solution. By contrast, silicates include stabilizing agents (sodium or potassium), which actually impede silica reacting with the lime. Colloidal silica is delivered more efficiently to the lime, allowing CSH to be formed quickly and more completely, with less work.
OmniSil Densifier’s superior efficiency means it is far faster and easier to apply than silicates, radically reducing labor costs and saving money overall on the densifying job.
Characteristics of OmniSil Densifier
- Low viscosity, allowing quick penetration of the surface
- Quick reaction time, within 1-2 minutes
- Zero potential for whiting
- Does NOT contribute to alkali-silica-reaction (ASR) which can cause swelling and cracking
- Low pH of 9
- NO high alkali surface residue
- NO rinsing required
- NO volatile organic compounds (VOC)
- Consistent 3-5 nm size particles
OmniSil Densifier is the most efficient way to densify, harden, and increase abrasion-resistance of concrete surfaces. OmniSil ships as a concentrate, reducing shipping costs. OmniSil offers you a faster, cleaner, greener and more profitable way to densify concrete.