Type C fill is defined as native material excavated directly from a trench.
Understanding Type C Backfill
Type C backfill, often used in construction and excavation projects, specifically refers to the soil or material that is dug out of a trench. Instead of importing new material from an external source, this excavated native material can be reused as backfill under certain conditions.
Using native material like Type C fill can be a cost-effective and environmentally friendly option, reducing the need for transportation of fill material. However, its suitability depends heavily on the properties of the soil itself.
Technical Requirements and Testing
For native material to qualify as Type C backfill, it must meet specific technical criteria related to its soil properties. These criteria are typically assessed through standardized laboratory tests. The provided reference specifies two key tests and their limits:
Required Soil Tests for Type C Fill
| Test | Standard | Requirement |
|---|---|---|
| Liquid Limit | ASTM D 423 | Shall not exceed 35 |
| Plasticity Limit | ASTM D 424 | Shall not exceed 12 |
- Liquid Limit (ASTM D 423): This test determines the water content at which soil transitions from a plastic to a liquid state. For Type C fill, the soil must not become liquid easily, indicated by a liquid limit not exceeding 35. This helps ensure the soil retains structural integrity.
- Plasticity Limit (ASTM D 424): This test measures the water content below which soil is no longer plastic. The difference between the liquid limit and the plasticity limit is the plasticity index, which indicates the range of water content over which the soil is plastic. For Type C fill, the plasticity limit shall not exceed 12, suggesting the soil is not excessively plastic and can be compacted effectively.
Meeting these requirements ensures that the native excavated material is suitable for use as backfill, providing adequate support and stability for the trench or structure it is filling.
