Bonding Admixture
Definition: A bonding admixture is a substance added to a cementitious material to improve its adhesive properties, allowing it to bond more effectively to a substrate.
Primary Function:
- Enhance the bond strength between new and existing concrete or mortar surfaces.
Applications:
- Used in repair works for concrete structures.
- Essential in overlays, toppings, and patches where new material is bonded onto the old.
- Important in cases where a strong bond is required to prevent delamination.
Types:
- Latex-based: Commonly used types include styrene-butadiene rubber (SBR) and acrylic polymers.
- Non-latex options may include silicones and other synthetic compounds.
Benefits:
- Improved adhesion and cohesion.
- Enhanced tensile and flexural strength.
- Increased durability and resistance to cracking.
- Better impermeability, reducing moisture ingress and subsequent issues like freeze-thaw damage.
Application Considerations:
- Surface preparation: Surfaces must be clean, free of dust, oils, and loose particles.
- Mix proportions: Accurate blending as per manufacturer guidelines is crucial.
- Curing: Proper curing practices must be followed to achieve optimal bonding strength.
Additional Points
Selection Criteria:
- Consider the type of repair or overlay required.
- Evaluate the environmental conditions to which the structure will be exposed.
- Assess compatibility with existing materials.
Limitations:
- May not be effective if the substrate is weak or deteriorated.
- Requires precise application techniques to achieve full potential.
Practical Tips
- Always follow manufacturer instructions for mixing ratios and application methods.
- Conduct a bond test on a small area before full-scale application.
- Ensure temperature and humidity conditions are within suitable ranges during application.
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