CONCRETE HARDENERS AND DENSIFIERS

Liquid hardeners and chemical densifiers change the molecular structure of the surface of concrete making it denser and/or stronger. On their own, they do not change the appearance of the concrete. Both are effective for minimizing the release of dust from a concrete floor, and when combined with grinding and polishing a durable and beautiful surface can be created. There are three basic categories of hardeners and densifiers in use today. Here is a brief description of each:

SILICATES

The oldest types of concrete hardeners are Silicates. A concrete hardener does just that – it makes the concrete surface harder. The family of Silicates are not the best sealers for concrete. 

There are 4 basic kinds of Silicate-based hardeners on the market. In each product the Silicate is combined with another mineral:

• Magnesium Fluorosilicates – have been around for over 100 years. Requires multiple applications with various rates of dilution followed by rinsing.
• Sodium Silicates – also requires multiple applications, scrubbing, and rinsing.
• Potassium Silicates – mostly used in Europe as a result of easier access to potassium.
• Lithium Silicates – This combination was developed to combat Alkali Silica Reaction (ASR). Where Sodium or Potassium Silicates are frequently exposed to water they can re-soluabilize, raising PH levels and eventually causing the concrete to weaken, crack, and generally disintegrate. The Lithium Silicates are less susceptible to ASR because the lithium stabilizes the silicate more efficiently. This results in improved performance while maintaining lower PH levels, resulting in longer life for the concrete.
• Application of Silicate products averages about 200 square feet per gallon

It is important to be aware that Silicates require some special care when using. Disposal of the rinse water is currently an ecological issue and waste water must be disposed of as a hazardous material. Use of Silicates also carries health risks – they have been directly linked to silicosis and have also been tagged as a carcinogen.

SILICINATES

The Silicinates are excellent at sealing the surface of concrete, and are better at resisting abrasion than Silicates. However, they do not harden the concrete the way that Silicates can. The life expectancy for Silicinates is 18 to 24 months, and then it is necessary to reapply the product.

• Silicinates are either Potassium or Sodium based
• Silicinates are applied the same way as Silicates
• Silicinates seal the surface of the concrete
• Silicinates do not harden the concrete
• There is significant research that documents the ill effects of sodium and  potassium silicates, and silicinates, on reactive aggregate in concrete. 
• Application rate?

Silicinates also require care when using. Just like Silicates, the rinse water is suspected of being a hazard to the environment and must be disposed of as hazardous material. It is important to know that Silicinates have also been tagged as a carcinogen.

BASIC APPLICATION PROCESS FOR SILICATES AND

SILICINATES:

• Spread and work in
• Mist with water to reactivate
• Allow to gel a second time
• Rinse & wet vac to remove

SILICAS

The newest and most promising of the chemical hardeners are the Silicas. They penetrate and harden the surface of the concrete, and are also an excellent sealer. Many feel that amorphous Silicas are currently the best technology for chemical densifiers and hardeners.     

• Silicas have up to 2X the abrasion resistance of Silicates or Silicinates
• Silicas do not contribute to ASR since the product is neutral 6.5.
• Silicas produce no hazardous waste 
• Silicas will not contribute to sweating or efflorescence
• Silicas performance is not contingent on dwell time
• Silicas reduce labor

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BASIC APPLICATION PROCESS FOR SILICAS:

•  Spray evenly on the surface of the clean slab (void of any curing compound)
•  Allow to dry thoroughly
•  Proceed with polishing process

Application rates are between 400 to 600 square feet per gallon. Scrubbing and

re-application of the product is not necessary at all. There is no waste material to

dispose of. Silicas do not contribute to silicosis and are not tagged as carcinogens.