Which Non Shrink Grout Is Best for Anchor Bolts?
Anchor bolt grouting is a critical part of structural and mechanical installations. Anchor bolts must transfer loads reliably from steel or machinery components into concrete without movement, loosening, or settlement. Choosing the right non shrink grout ensures strong bond, high compressive strength, and full contact with both concrete and steel surfaces. Below is a practical guide to the best non shrink grout types and features for anchor bolt applications.
Why Anchor Bolts Need Non Shrink Grout
Ordinary cement grout shrinks during curing, which can create voids around bolts and reduce load transfer capacity.
- Shrinkage can loosen anchor bolts over time
- Voids around bolts weaken structural connections
- Dynamic loads and vibration increase risk of failure
- Water and environmental exposure worsens issues
Non shrink grout compensates for shrinkage and maintains solid contact throughout the load-bearing area.
Key Properties for Anchor Bolt Grout
The best non shrink grout for anchor bolts should have these characteristics:
- High compressive strength to support loads
- Zero shrinkage or controlled expansion to prevent voids
- Good adhesion to metal and concrete
- Workability for tight pockets and bolt holes
- Suitable setting time depending on schedule
Top Types of Non Shrink Grout for Anchor Bolts
Several non shrink grout formulations are suitable, depending on load and site requirements.
1. High Strength Flowable Grout
Flowable non shrink grout with high compressive strength is often the best choice.
- Flows easily into narrow bolt pockets
- Eliminates air pockets and voids
- Maintains volume and strength
- Good for precision and dynamic loads
2. Plastic Non Shrink Grout
Plastic (medium consistency) grout can be used where controlled placement is preferred.
- Better for slightly larger pockets
- Easy to place without vibration
- Strong bond with steel and concrete
- Good for anchor bolts in structural elements
3. Rapid Setting Non Shrink Grout
Rapid hardening grout is useful where time constraints are critical.
- Develops strength quickly
- Allows early loading of bolts
- Ideal for shutdowns and repairs
Features of the Best Grout for Anchor Bolts
When selecting a non shrink grout for anchor bolts, look for these performance attributes.
- Compressive strength: Typically 30–50 MPa or higher
- Controlled expansion: Ensures full contact without pushing bolts
- Good flowability: Reaches all voids and pockets around bolts
- Chloride-free: Prevents corrosion of steel fixings
- Low permeability: Reduces moisture ingress
Installation Considerations for Anchor Bolts
Proper installation is as important as grout selection.
- Clean bolt pockets and remove loose debris
- Pre-wet concrete surfaces to saturated surface dry state
- Use formwork or containment for vertical and overhead pockets
- Pour grout slowly to avoid trapping air
- Avoid vibration during placement
When to Use Specific Grout Types
Choose based on load, accessibility, and schedule:
- Flowable grout: Best for narrow pockets and heavy loads
- Plastic grout: Better for accessible and larger anchor pockets
- Rapid setting grout: When early load return is required
Signs You Chose the Right Grout
After grouting, the following indicate good performance:
- No voids around bolts
- Full contact between grout and bolt/concrete
- Consistent strength gain with curing
- Stable and vibration-free connection under load
Frequently Asked Questions (FAQ)
1. Can ordinary grout be used for anchor bolts?
No, ordinary grout shrinks and can loosen bolt contact over time.
2. Does non shrink grout prevent corrosion?
Non shrink grout reduces moisture paths but is not a corrosion inhibitor; chloride-free formulation helps protect steel.
3. How soon can bolts be loaded after grouting?
Load only after grout reaches required strength—typically 24–72 hours, depending on grade and conditions.
4. Is vibration needed when placing grout?
No, vibration can trap air and disrupt volume stability.
5. Can non shrink grout be used outdoors?
Yes, with proper curing and protection.
Raltro
Raltro is a construction materials insight platform focused on helping engineers and site professionals match materials to real project demands. By explaining which non shrink grout variants are best for anchoring bolts, key performance qualities to look for, and how proper installation affects long-term reliability, Raltro supports decision-making that improves connection strength, structural integrity, and durability in both industrial and building applications.