Crusher stone grit—often referred to as construction aggregate—is a crushed stone material used in concrete, foundations, road layers, and various structural applications. It is produced by crushing large stones into specific sizes that meet engineering requirements.
The size of the grit matters because every construction activity needs a particular particle size for strength, stability, and workability.
- Bigger stones improve load-bearing capacity
- Medium sizes ensure good compaction
- Smaller sizes help in smooth finishes and dense concrete
Understanding various grit sizes helps builders, engineers, and contractors choose the right material for each task.
1. Detailed Explanation of Each Crusher Stone Grit Size
40mm Crusher Stone Grit
What 40mm size means
These are coarse aggregates sized around 40 millimetres—large, strong, and primarily used where high load-bearing strength is required.
Common Applications
- Base layers for roads and highways
- Railway ballast (in some cases)
- Foundation fillings for heavy structures
- Under-layer for RCC footings
- Drainage layers
Benefits
- Excellent load distribution
- Strong interlocking for stability
- Allows water movement, improving drainage
- Ideal for deep foundation filling
When NOT to Use 40mm Grit
- Not suitable for RCC slabs
- Not recommended for beams and columns
- Avoid in flooring or plaster-concrete mixes
20mm Crusher Stone Grit
What 20mm size means
A standard aggregate size used in most structural concreting works. Typically 16–20 mm clean and angular stones.
Construction Applications
- RCC slabs
- Columns and beams
- Footings
- Pathways and general concrete work
- Paver block manufacturing (base concrete)
Benefits
- Excellent strength for structural concrete
- Good compaction without voids
- Ideal balance between workability and load-bearing
When NOT to Use 20mm Grit
- Thin flooring layers
- Fine finishing surfaces
- Micro concrete or repair mortar
12mm Crusher Stone Grit
What 12mm size means
Medium-sized aggregate used where smoother concrete and better finish is required.
Construction Applications
- Residential slabs
- Walkways
- Light foundation concrete
- Pathway concreting
- Paver block top-layer concrete
Benefits
- Provides smoother finish
- Improves workability of concrete
- Suitable for thinner sections
When NOT to Use 12mm Grit
- Heavy-duty foundations
- High-strength columns/beams
- Road base work
10mm Crusher Stone Grit
What 10mm size means
Small-sized aggregate commonly used in fine concrete mixes and detailed construction work.
Construction Applications
- Floor concrete
- Plaster base concrete
- Small-section RCC
- Precast concrete items
- Paver block bedding
Benefits
- High workability
- Smooth finish
- Good bonding in thin concrete sections
When NOT to Use 10mm Grit
- Heavy RCC structures
- High-load foundations
- Road compaction layers
6mm Crusher Stone Grit
What 6mm size means
Fine aggregates typically used where dense, smooth mixtures are required.
Construction Applications
- Interlocking tile bedding
- Paver block bedding
- Pathway finishing
- Decorative landscaping
- Thin topping layers
Benefits
- Excellent for dense compaction
- Smooth surface finish
- Easy spreadability
- Useful for aesthetic and non-load applications
When NOT to Use 6mm Grit
- Structural concrete of any type
- Load-bearing foundations
- Road base layers
2. Comparison Table: Crusher Stone Grit Sizes
| Size | Best Use | Load-Bearing Capacity | Workability | Suitable For |
| 40mm | Foundations, roads, drainage | Very High | Low | Road base, footings, heavy foundations |
| 20mm | RCC, beams, slabs | High | Moderate | Structural RCC, columns, beams, slabs |
| 12mm | Light concrete, residential slabs | Medium | High | Light RCC, pathways, pavers |
| 10mm | Flooring, precast, finishing concrete | Medium-Low | Very High | Floors, thin RCC, precast elements |
| 6mm | Paver bedding, landscaping | Low | Excellent | Paver bedding, tiles, decorative work |
3. Engineering Perspective
How grit size affects strength
- Larger aggregates distribute loads better
- Smaller aggregates fill gaps, improving density
- Proper gradation improves the concrete’s overall compressive strength
Workability of concrete
- Small-sized grit increases workability
- Large-sized grit may make concrete stiff
- Ideal mixes use a combination of sizes for balance
Drainage performance
- Bigger particles create channels for water flow
- Used in road bases and foundation fillings
- Prevents waterlogging and soil weakness
Interlocking and compaction
- Angular stones interlock better than rounded stones
- Larger grit increases stability in foundation layers
- Smaller grit compacts easily, creating a dense surface
4. How to Choose the Right Grit Size
For RCC Slabs
- Ideal: 20mm
- Optional for thin slabs: 12mm
For Columns & Beams
- Use 20mm for maximum structural strength
For Road Construction
- Base layer: 40mm
- Top layer: 20mm
For Foundation Bases
- Use 40mm for deep foundations
- Secondary layer: 20mm
For Landscaping
- Decorative finish: 6mm
- Pathway concrete: 12mm
For Paver Block Bedding
- Preferred: 6mm / Quarry dust-free fine grit
5. Quality Checkpoints When Buying Crusher Stone Grit
1. Angular Shape
- Angular stones interlock better
- Avoid round river stones for concrete work
2. Cleanliness
- No clay, dust, or soil contamination
- Clean aggregates improve bonding
3. Proper Gradation
- Balanced mixture of particle sizes
- Ensures durability and strength
4. Meets Indian Standards
For construction aggregates, IS 383:2016 defines:
- Size tolerance
- Shape
- Water absorption
- Density
- Flakiness and elongation index
5. Hardness & Durability
Stones should be:
- Hard
- Weather-resistant
- Not flaky or elongated
6. Common Mistakes to Avoid
Using the Wrong Size for RCC
- Using 40mm in slabs reduces compaction
- Using 6mm in RCC reduces strength
Mixing Dust with Grit
- Excessive dust weakens concrete
- Reduces bonding
Poor Compaction
- Leaves voids
- Reduces load-bearing capacity
Buying Untested Material
- Non-graded grit leads to inconsistent strength
- Always choose verified suppliers and tested aggregates
Conclusion
Choosing the correct crusher stone grit size is essential for achieving structural strength, long-term durability, and safe construction performance. Each grit size—40mm, 20mm, 12mm, 10mm, and 6mm—has a distinct purpose in the construction ecosystem. With the right selection, proper gradation, and verified quality, builders can ensure stronger foundations, better RCC structures, improved workability, and long-lasting results in every project.
For builders who want dependable, well-graded aggregates for any type of construction work, Raj Mineral offers a complete range of crusher stone grit sizes backed by consistent quality and trusted performance.
