Case Study: the waterglass, waterproofing agent for concrete

Modello della catena silicatica

What is the WATERGLASS?

The water glass is a chemical substance known in past centuries. Since 1825, thanks to Johan Nepomuk von Fuchs, the industrial production of soluble sodium silicates was analyzed, known as "liquid glass" (waterglass). The waterglass is nothing more than sodium silicate.

xSiO2 * Na2O

where the ratio between sodium and silicate (x) may vary between 0.50 and 3.75 to a molar basis. On the market there are several products based on soluble glass, which differ typically for the components added to meet various needs.

In the proprietary formula of Ecobeton, the sodium silicate is added a special catalyst (Evercrete ®) which allows the waterglass to penetrate deep into the concrete and seal the cement matrix permanently. The waterglass becomes Evercrete Vetrofluid.

How does it work?

The reaction, which is unleashed by impregnating the porous concrete with Evercrete Vetrofluid, leads to the formation of a gel based on calcium silicate and lye:

Ca(OH)2 + Na2O * xSi = O2 + 2NaOH.

This reaction occurs thanks to free calcium hydroxide, a concrete component. In Figure 1 you can see a capillary pore of the concrete impregnated with Evercrete Vetrofluid

Reazione chimica del silicato nei pori

In the figure the diagram of a impregnated pore (left) with calcium diffusion from the concrete mass and subsequent precipitation of the gel and constriction of the pore after impregnation (right)

Results

The water glass involves a precipitation of solid substances in the pores with a consequent reduction of the middle section of the pores of the impregnated layer. This reaction involves:

  1. decrease in water permeability under pressure;
  2. decrease in capillary water intake;
  3. decrease of the diffusion of water-soluble ions such as chlorides;
  4. decrease of the diffusion of gases, such as water vapour.
Distribuzione dei pori su calcestruzzo trattato

Figure 2 - mercury porosimeter test to determine pores constriction

Thanks to Evercrete® catalyst, the effect is dramatically amplified thanks to the depth of penetration (up to 40 mm), making Evercrete Vetrofluid a high performance protection and waterproofing agent, with CE Mark level 2 + according to UNI EN 1504-2 "Protection and repair of concrete structures."




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