Yes, you can use sharp sand as part of a sub-base, particularly for paving projects.
Sharp sand, also known as coarse sand or grit sand, is a versatile aggregate often used in construction and landscaping. Unlike soft or builder's sand, it contains a higher percentage of larger, angular particles, which gives it a gritty texture. This characteristic makes it suitable for specific applications within a sub-base structure.
Understanding Sharp Sand in Sub-Base Applications
According to the provided information, Sharp Sand contains a high percentage of large particles for a gritty texture and better results when used as part of a sub-base for paving, on top of Type 1 MOT.
This tells us a few key things about its use:
- Particle Size and Texture: Its large particles and gritty texture contribute to better performance in certain applications compared to finer sands.
- Specific Application: It is highlighted as suitable for sub-bases related to paving.
- Layer Structure: It is specifically mentioned as being used on top of Type 1 MOT. This indicates it's typically not the entire sub-base but a layer within it.
Why Use Sharp Sand in a Sub-Base?
The unique properties of sharp sand make it beneficial in specific layers of a sub-base:
- Compaction: The angular nature of the particles helps them lock together, aiding in compaction and creating a stable layer.
- Drainage: Its coarse nature can allow for better drainage compared to finer sands or other materials, which is crucial for the longevity of paved surfaces.
- Bedding Layer: Often, a layer of sharp sand is used directly on top of the main sub-base material (like Type 1 MOT) as a bedding layer upon which paving slabs or blocks are laid. This provides a level and stable surface for the final paving layer.
Sharp Sand vs. Type 1 MOT
It's important to understand that sharp sand is generally used in conjunction with or on top of a primary sub-base material like Type 1 MOT (Ministry of Transport).
- Type 1 MOT: This is a granular sub-base material consisting of crushed stone or concrete with a specific particle size distribution (typically 40mm down to dust). It forms the main load-bearing layer of the sub-base.
- Sharp Sand: As highlighted in the reference, it's used on top of the Type 1 MOT layer for paving applications, acting as a fine levelling and bedding layer.
| Material | Typical Composition | Primary Use in Paving Sub-base | Key Characteristic |
|---|---|---|---|
| Type 1 MOT | Crushed stone/concrete (40mm down) | Main load-bearing layer | Excellent compaction, forms structural base |
| Sharp Sand | Coarse sand (approx. 0-4mm particle size) | Bedding/levelling layer | Gritty texture, helps with drainage and fine levelling |
Practical Application
When building a sub-base for a patio or driveway, the typical layers might look like this (from the bottom up):
- Excavated Ground: Prepared and compacted.
- Geotextile Membrane (Optional but Recommended): Separates soil from sub-base and prevents weed growth.
- Type 1 MOT: Laid and compacted to form the primary structural layer. This is where most of the load-bearing capacity comes from.
- Sharp Sand (or Grit Sand): A layer (typically 25-50mm thick) spread and screeded level on top of the compacted Type 1 MOT. This acts as the bedding layer for the paving units.
- Paving Slabs or Blocks: Laid directly onto the sharp sand bedding layer.
- Jointing Material: Sand or mortar to fill the gaps between paving units.
Using sharp sand in this manner, on top of a well-compacted Type 1 MOT layer, provides the necessary stability and smooth surface for laying paving, leading to a durable and effective paved area.
