Sodium silicate (commonly known as water glass or sodium metasilicate) is a versatile inorganic compound widely used in industrial and civil applications. Its main uses can be categorized as follows:

I. Construction and Building Materials

1. Concrete Enhancer
   • Performance Improvement: Increases cement density and impermeability, reduces permeability by over 50%, and mitigates chloride ion corrosion of steel reinforcement.
   • Crack Repair: Serves as grouting material for rapid repair of wall cracks and foundation reinforcement.
   • Fireproofing: Forms an insulating layer at high temperatures to delay fire spread, used in refractory bricks and fire-resistant coatings.
2. Waterproofing and Solidification
   • Coats building surfaces to form a waterproof membrane, resisting moisture penetration;
   • Acts as a soil stabilizer to improve foundation stability.

II. Chemical and Daily Chemical Manufacturing

1. Detergent Additive
   • Synergistic Cleaning: Maintains alkaline conditions in laundry detergents, enhances emulsification and foam stability, and prevents caking;
   • Water Softening: Works with sodium carbonate to remove calcium and magnesium ions, improving cleaning efficiency.
2. Raw Material Processing
   • Produces derivatives such as silica gel, white carbon black, zeolite molecular sieves, and sodium metasilicate pentahydrate;
   • Serves as a soap filler to enhance cleaning effectiveness.

III. Industrial Auxiliary Applications

1. Casting and Ceramics
   • Sand Molding Bonding: Sodium silicate with a modulus of 3.2–3.4 is used in high-temperature sand casting for its strong adhesion;
   • Ceramic Fluxing: Lowers sintering temperature and improves green body strength and glaze performance.
2. Textiles and Papermaking
   • Acts as a dyeing auxiliary to enhance dye adhesion and as a sizing agent in papermaking to improve paper strength.
3. Precision Cleaning
   • Removes grease residues from metal parts and is compatible with precision instrument cleaning.

IV. Other Fields

• Agriculture: Used in silicon fertilizer production to improve crop disease resistance and fruit quality;
• Environmental Protection: Precipitates impurities in wastewater treatment and serves as an auxiliary in flue gas desulfurization;
• Wood Preservation: Inhibits fungal erosion to extend service life.

?? Usage Precautions

• Strong Alkali Protection: Avoid skin contact with high-concentration solutions; use protective equipment during operation;
• Industrial Standard Differentiation: Food-grade and industrial-grade products must not be mixed; exports require MSDS/ROHS certification.

Note: The modulus of sodium silicate (SiO?/Na?O ratio) directly affects its performance. For example, low modulus (2.4–2.8) is suitable for cement additives, while high modulus (3.0–3.4) is used in casting bonding.