What Is Non Shrink Grout and How It Works
Non shrink grout is a specialised cementitious material used in construction where precise load transfer, dimensional stability, and long-term durability are required. Unlike ordinary cement grout, non shrink grout is designed to maintain its volume after placement and curing. This makes it ideal for structural applications where even minor shrinkage can lead to voids, loss of contact, vibration, or structural weakness. Understanding what non shrink grout is and how it works helps engineers, contractors, and site teams apply it correctly and achieve reliable, long-lasting results.
What Is Non Shrink Grout?
Non shrink grout is a factory-formulated cement-based grout that compensates for plastic and drying shrinkage during the curing process. It is supplied as a dry, pre-mixed powder containing cement, graded aggregates, and special additives. When mixed with water in the correct proportions, it produces a flowable or plastic grout that fills gaps completely and remains dimensionally stable after hardening.
Unlike conventional cement grout, which tends to shrink as water evaporates, non shrink grout is engineered to either maintain its original volume or expand slightly in a controlled manner. This ensures full contact between the grout and surrounding concrete or steel elements.
Why Shrinkage Is a Problem in Construction
Shrinkage in grout or concrete can cause serious performance issues, especially in load-bearing and precision applications.
- Shrinkage creates voids beneath base plates and structural elements
- Voids reduce load transfer efficiency
- Uneven support can lead to vibration and movement
- Structural elements may crack or fail prematurely
- Machinery alignment can be affected
Non shrink grout eliminates these risks by ensuring that the hardened grout remains fully bonded and in contact with the supported element.
Main Components of Non Shrink Grout
Non shrink grout is made from carefully selected materials that work together to achieve volume stability and strength.
- Cement: Provides strength and binding properties
- Graded aggregates: Improve packing density and reduce voids
- Shrinkage-compensating additives: Control expansion and prevent volume loss
- Plasticisers: Improve flow and workability
- Stabilisers: Ensure consistent performance during curing
Each component plays a specific role in ensuring that the grout performs predictably under site conditions.
How Non Shrink Grout Works
Non shrink grout works by compensating for the natural shrinkage that occurs during cement hydration and drying. This is achieved through controlled expansion mechanisms built into the formulation.
Plastic Stage Compensation
During the early plastic stage, non shrink grout undergoes slight expansion. This offsets the settlement that normally occurs before the grout hardens.
Hardened Stage Stability
Once hardened, the grout maintains its volume and does not shrink away from contact surfaces. This ensures continuous load transfer and long-term stability.
Full Contact and Load Transfer
By maintaining full contact between the grout, concrete, and steel elements, non shrink grout ensures that loads are distributed evenly and efficiently.
Types of Non Shrink Grout
Non shrink grouts are available in different consistencies and strength grades to suit various applications.
- Flowable grout: Used where grout needs to flow into tight gaps and voids
- Plastic grout: Used for thicker sections or sloped surfaces
- High-strength grout: Used for heavy machinery and structural elements
- Rapid-setting grout: Used where early strength gain is required
Selecting the correct type is essential for proper performance.
Common Applications of Non Shrink Grout
Non shrink grout is used in a wide range of construction and industrial applications.
- Machinery base plates and equipment foundations
- Column base plates and steel structures
- Anchor bolts, dowels, and starter bars
- Structural repairs and void filling
- Precast concrete installations
- Bridge bearings and infrastructure works
In each of these applications, dimensional stability is critical.
Importance of Proper Mixing
Correct mixing is essential for non shrink grout to perform as intended.
- Always follow manufacturer-recommended water ratios
- Use clean water and mixing equipment
- Avoid adding excess water to improve flow
- Mix until a uniform, lump-free consistency is achieved
Improper mixing can reduce strength and compromise shrinkage compensation.
Installation and Placement Process
Non shrink grout must be placed carefully to ensure complete filling and performance.
- Prepare surfaces by cleaning and removing loose materials
- Pre-wet concrete surfaces without leaving standing water
- Install formwork to prevent leakage
- Pour grout continuously from one side to avoid air entrapment
- Ensure proper venting for air escape
Good workmanship is just as important as material quality.
Curing of Non Shrink Grout
Proper curing improves strength development and durability.
- Protect grout from rapid moisture loss
- Use curing compounds or wet coverings if required
- Avoid loading the grout before it reaches required strength
- Follow curing time recommendations
Poor curing can lead to cracking and reduced performance.
Advantages of Non Shrink Grout
Non shrink grout offers several advantages over conventional cement grout.
- No volume loss after curing
- High compressive strength
- Excellent load transfer capability
- Reduced vibration and movement
- Improved durability and service life
These advantages make it the preferred choice for critical applications.
Limitations of Non Shrink Grout
While highly effective, non shrink grout must be used correctly.
- Higher cost compared to ordinary cement grout
- Requires proper mixing and placement
- Not suitable as a replacement for structural concrete
Understanding its limitations ensures appropriate use.
Common Mistakes to Avoid
Avoiding common site errors helps achieve best results.
- Adding extra water to improve flow
- Poor surface preparation
- Inadequate formwork sealing
- Loading the grout too early
Attention to detail prevents performance issues.
Frequently Asked Questions (FAQ)
1. Is non shrink grout stronger than cement grout?
Yes, it generally provides higher compressive strength and better load transfer.
2. Can non shrink grout crack?
When mixed and cured properly, it resists shrinkage-related cracking.
3. Is non shrink grout waterproof?
It resists water penetration but is not a replacement for waterproof membranes.
4. Can non shrink grout be used outdoors?
Yes, with proper curing and protection.
5. How long does non shrink grout last?
When correctly applied, it lasts for the life of the structure.
Raltro
Raltro is a construction materials knowledge platform focused on explaining how specialised products function in real construction environments. By breaking down what non shrink grout is, how it works, and why it is essential for structural stability, Raltro helps engineers, contractors, and site professionals understand correct usage, avoid common mistakes, and achieve reliable, long-term performance in both building and infrastructure projects.