What is Sodium Silicate?
Sodium silicate, also known as water glass, is a soluble silicate formed by the combination of alkali metal oxides and silicon dioxide. Its chemical formula is Na₂O·nSiO₂. Its appearance is usually a thick transparent or light yellow liquid, and it also has a solid form.
It possesses several key characteristics that make it an ideal material for leak sealing:
·Strong adhesion: Capable of effectively bonding with other materials.
·Acid resistance: Exhibits good resistance to most inorganic acids.
·Curing adjustable: The curing time can be precisely controlled by adding curing agents (such as calcium chloride, aluminum sulfate, etc.).
·Permeability: The liquid sodium silicate can penetrate into tiny cracks and pores.
In industry, sodium silicate is widely used in the production of adhesives, soaps, detergents, as well as being employed as a waterproofing agent and leak stopper.
The Core Principle of Sodium Silicate Leakage Sealing
Sodium silicate leakage sealing does not rely on physical filling; instead, it is based on a clever chemical reaction. The core principle is as follows: The liquid silica sodium reacts with the curing agent to form insoluble silica gel (silica gel) and precipitates, thereby permanently blocking the water seepage channels.
This process mainly involves two reaction pathways:
1.Reaction with curing agent (most commonly used)
When the sodium silicate solution comes into contact with a divalent metal salt (such as calcium chloride CaCl₂) as the curing agent, a rapid chemical reaction occurs: Na₂SiO₃ + CaCl₂ → CaSiO₃↓ + 2NaCl
The generated calcium silicate (CaSiO₃) is a white, flocculent precipitate that is insoluble in water and possesses strong filling and consolidation capabilities. It can quickly interweave into a network within the cracks, forming a dense waterproof barrier.
2.Reacts with acidic substances
Sodium silicate is inherently alkaline. When it comes into contact with acidic substances or carbon dioxide in the leaking water, it will also slowly decompose and form silicic acid gel:
Na₂SiO₃ + CO₂ + H₂O → H₂SiO₃ (silica gel) + Na₂CO₃
The formed silica gel (H₂SiO₃) is also insoluble in water and can play a supplementary role in blocking and reinforcing.
In summary, sodium silicate leakage control is achieved through a chemical reaction, converting flowing liquids into insoluble solid precipitates, thereby “using water to control water” and transforming fluidity into stasis, fundamentally achieving the purpose of leakage prevention.
How to use sodium silicate for leak sealing? – Construction methods and steps
The construction methods of sodium silicate for leak sealing vary depending on the leakage situation (slow leakage, rapid flow, water gushing) and the project requirements. They are mainly divided into single liquid method and double liquid method.
1.Preparatory work:
Materials: Sodium silicate solution (commonly with a modulus of 2.4 – 3.3), curing agent (such as calcium chloride, aluminum sulfate, etc.), cement, accelerator, etc.
Tools: Grouting pump, mixer, bucket, chisel, hammer, brush, protective gloves and goggles.
2.Construction steps:
Basic treatment
Identify the weak points: Determine the exact location of the cracks or holes.
Clean the base surface: Use chisels, hammers, and other tools to carve the cracks into “V” or “U” shaped grooves. Remove the loose debris, dust, oil stains, etc. from the inside, and rinse it clean with water. This step is crucial as it ensures a proper contact between the sodium silicate and the base surface.
3.Selection methods and grouting
Method 1: Two-fluid grouting method (applicable to water gushing under pressure)
This is the most effective and commonly used method. A dual-fluid grouting pump is required.
Liquid A is a sodium silicate solution, and Liquid B is a curing agent (such as calcium chloride solution).
Two liquids are mixed in the mixer of the grouting pump or directly at the leakage point. They react instantly to form a solidified substance, immediately sealing the water flow.
Advantages: Quick response, excellent leak sealing effect, suitable for large-scale water gushing.
Method 2: Single liquid brushing / pressure grouting method (suitable for slow seepage and wet surfaces)
Brushing method: For walls that are not subject to significant water flow but are damp, a solution of sodium silicate can be directly applied to the surface. It will react with calcium ions in the base layer or CO₂ in the air to form a waterproof layer.
Single liquid pressure grouting: Mix sodium silicate solution with a small amount of retarder, and inject it into the cracks using a single liquid pump. The grout penetrates and flows within the cracks, slowly gels, and fills all the tiny voids.
4.Sealing and Reinforcement
For larger holes, after the initial water sealing is achieved using the two-fluid method, a cement mortar mixed with accelerators (such as water glass itself) is usually used for final sealing and leveling to enhance the structural strength.
5.Maintenance and Inspection
After the construction is completed, the leakage-affected area should be left to naturally cure for 24 to 48 hours.
After the maintenance is completed, conduct a water spraying or water storage test to check the leakage sealing effect and ensure there is no leakage.
Application Scenarios of Sodium Silicate Leak Sealing
Sodium silicate leak sealing is widely used in various fields due to its rapid, economical and effective characteristics:
Construction Engineering:
Basement leakage repair: Addressing cracks on the walls and floors as well as water seepage at construction joints.
Waterproofing for bathrooms and kitchens: Quick remediation for floor leakage.
Roof waterproofing repair: Addressing minor cracks.
Municipal and Water Conservancy Projects:
Sealing and waterproofing of water tanks, water towers and swimming pools.
Sealing of cracks in the dam and reservoir structures.
Seepage treatment of water supply tunnels and culverts.
Underground Engineering:
Water seepage blocking in subway tunnels and mine shafts.
Construction of the water-stop curtain for the underground continuous wall.
Emergency rescue and disaster relief:
Due to sudden water gushing caused by pipeline rupture or heavy rain, the double liquid grouting with sodium silicate is an effective emergency response method.
Sodium Silicate Stop Leak Advantages and Limitations
Advantages:
Low cost: The raw materials are readily available and the price is reasonable.
Effectiveness is rapid: The two-fluid method can achieve instant solidification and immediate water sealing.
Flexible construction: Various construction methods can be selected according to the situation.
Environmental friendliness: The main component is an inorganic substance, which is relatively friendly to the environment.
Limitations:
Limited durability: The generated silicone may partially dissolve over time under the erosion of flowing water, and is not suitable for dynamic cracks that are subjected to high water pressure for an extended period.
High brittleness: The consolidated material has poor flexibility and is not suitable for the expansion and contraction of the substrate.
The construction technology has high requirements: improper mixing ratio and control of the injection pressure will significantly reduce the effectiveness.
Frequently Asked Questions (FAQ)
Q1: How long can sodium silicate leak sealing last?
A: In static or environments with little pressure variation, the effect can last for several years or even longer. However, in dynamic cracks or under high-speed water flow impact, the lifespan will be shortened and may require regular maintenance or be used in combination with other materials (such as epoxy resin, polyurethane).
Q2: How are sodium silicate and cement used together?
A: It is commonly used as “quick-setting cement”. By replacing water with the sodium silicate solution when mixing the cement, the cement will solidify rapidly (usually within 1-2 minutes), and it is very effective for emergency sealing of holes.
Q3: Can one use sodium silicate to seal leaks at home?
A: For small, non-load-bearing structures with slow leakage, one can try applying a surface coating of sodium silicate solution. However, for severe leaks, especially in load-bearing walls or basements, it is strongly recommended to hire a professional waterproofing company, as incorrect operation may exacerbate the problem.
