Non Shrink Grout Mixing Ratio Guide
Correct mixing ratio is critical for non shrink grout to achieve its intended strength, flow, and shrinkage-compensating performance. Adding too much or too little water can significantly affect compressive strength, volume stability, and durability. This guide explains standard non shrink grout mixing ratios, how they vary by application, and best practices to ensure reliable results on site.
Why Mixing Ratio Is Important
Non shrink grout is factory-designed to perform within a specific water range. Incorrect mixing is one of the most common causes of grout failure.
- Too much water reduces strength and causes bleeding
- Too little water affects flow and complete void filling
- Incorrect ratio can reduce shrinkage compensation
- Proper mixing ensures full load transfer and durability
Standard Non Shrink Grout Mixing Ratio
Most cementitious non shrink grouts are supplied in 25 kg bags and require controlled water addition.
Typical Water Requirement
- Flowable consistency: 3.5 – 4.0 litres per 25 kg bag
- Plastic consistency: 3.0 – 3.4 litres per 25 kg bag
- Stiff / trowellable consistency: 2.8 – 3.0 litres per 25 kg bag
Note: Always follow the product datasheet, as ratios may vary slightly between brands.
Mixing Ratio by Application Type
Different applications require different grout consistencies.
Flowable Grout (Base Plates & Machinery)
- Water: Higher end of recommended range
- Purpose: Easy flow into tight gaps and voids
- Used for: Machinery bases, large base plates, precast seating
Plastic Grout (Columns & Structural Gaps)
- Water: Mid-range of recommendation
- Purpose: Controlled placement without segregation
- Used for: Column bases, anchor pockets, structural repairs
Stiff Grout (Vertical & Sloped Areas)
- Water: Lower end of recommendation
- Purpose: Prevent grout from flowing out
- Used for: Sloped surfaces, overhead or edge repairs
Step-by-Step Mixing Procedure
Following the correct mixing process ensures consistent performance.
- Measure the required water accurately
- Add water into a clean mixing container
- Gradually add grout powder while mixing
- Mix using a mechanical mixer for 3–5 minutes
- Achieve a uniform, lump-free consistency
Avoid hand mixing for structural applications, as it leads to inconsistent results.
Mixing Equipment Recommendations
Using proper equipment improves grout quality.
- Low-speed drill (400–600 rpm)
- Grout paddle or helical mixer
- Clean buckets or grout mixers
- No contamination from previous mixes
Common Mixing Mistakes to Avoid
These errors can seriously affect grout performance.
- Adding extra water to improve flow
- Estimating water instead of measuring
- Mixing too fast and trapping air
- Re-tempering grout after it starts setting
Effect of Water Content on Grout Performance
Water content directly impacts grout behavior.
- Higher water reduces compressive strength
- Excess water increases bleeding and segregation
- Low water improves strength but reduces flow
- Correct ratio balances flow and strength
Temperature Considerations During Mixing
Ambient temperature affects grout workability and setting time.
- Hot weather: Use cool water and work quickly
- Cold weather: Use normal water and protect from low temperatures
- Avoid mixing in extreme conditions
Batch Mixing and Consistency Control
For large pours, consistency must be maintained.
- Use the same water ratio for every batch
- Mix full bags whenever possible
- Keep records of water quantity used
- Assign one person to control mixing
Placement Time After Mixing
Non shrink grout has a limited working time.
- Place grout immediately after mixing
- Do not delay placement
- Do not add water once setting begins
Frequently Asked Questions (FAQ)
1. Can I add more water if grout feels stiff?
No, adding water reduces strength and affects performance.
2. Is flowable grout always better?
No, the consistency should match the application.
3. Can I mix half a bag?
Yes, but water must be reduced proportionally and measured accurately.
4. Does mixing time affect grout quality?
Yes, insufficient mixing leads to uneven strength and flow.
5. Can grout be remixed after resting?
No, re-mixing after initial set damages performance.
Raltro
Raltro is a construction materials knowledge platform focused on practical site execution and material performance. By explaining correct non shrink grout mixing ratios, application-specific consistencies, and common site mistakes, Raltro helps engineers, contractors, and applicators achieve consistent strength, proper load transfer, and long-term durability in structural grouting works.