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D5874-24 – Standard Test Method Technical Guide
📐 Test Methods and Scope
These test methods cover the determination of the Impact Value (IV) of a soil either in the field or in a test mold. Four procedures are provided: Field Procedure A for IV alone, Field Procedure B for IV and water content, Field Procedure C for IV, water content and dry density, and a Mold Procedure for lab compaction. The standard is applicable for unsaturated compacted fills, pavement materials, soils, and soil-aggregates with maximum particle sizes less than 37.5 mm (1.5 in.) using the standard 4.5 kg hammer.
Values are stated in SI units, with inch-pound units provided for information. Reporting in non-SI units is not considered nonconformance. All observed and calculated values must conform to significant digits and rounding guidelines in Practice D6026.
⚠️ This standard does not purport to address all safety concerns. Users must establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
⚙️ Equipment and Hammer Selection
The standard hammer is a 4.5 kg (10 lbm) hammer for general use. For lower strength soils, such as fine-grained cohesionless or highly organic soils, lighter hammers of 0.5 kg (1.1 lbm) or 2.25 kg (5 lbm) are used, with maximum particle size less than 9.5 mm (0.375 in.). For harder materials, heavier hammers of 10 kg (22 lbm) or 20 kg (44 lbm) are applicable.
| ⚙️ Hammer Mass | 📏 Application | 🟦 Max Particle Size |
|---|---|---|
| 0.5 kg (1.1 lbm) | Lower strength soils, turfgrass | <9.5 mm (0.375 in.) |
| 2.25 kg (5 lbm) | Lower strength soils | <9.5 mm (0.375 in.) |
| 4.5 kg (10 lbm) | Standard, unsaturated compacted fills | <37.5 mm (1.5 in.) |
| 10 kg (22 lbm) | Harder materials | N/A |
| 20 kg (44 lbm) | Harder materials | N/A |
📊 Key Measured Properties and Correlations
The Impact Value (IV) is determined from the deceleration of the hammer upon impact. For the standard 4.5 kg hammer, IV can be correlated with unsoaked California Bearing Ratio (CBR) through laboratory tests for a particular soil. For lighter hammers, IV can be independently correlated to unsoaked CBR or used to infer percentage compaction for lower strength soils. All measurements must adhere to significant digits and rounding rules.
| 🔍 Hammer Mass | 📐 Correlation | 🎯 Typical Application |
|---|---|---|
| 4.5 kg (10 lbm) | IV correlated with unsoaked CBR | Standard soils, pavement materials |
| 0.5 kg (1.1 lbm) and 2.25 kg (5 lbm) | IV correlated to unsoaked CBR or percentage compaction | Lower strength soils |
💡 For comparing measured or calculated values with specified limits, round to the nearest decimal or significant digits as per the specified limits in the standard.
❓ Frequently Asked Questions
🔍 What is the Impact Value (IV)?
The Impact Value (IV) is a measure of soil strength determined by dropping a hammer of specified mass onto the soil or compacted sample. It is also known as Clegg Impact Value (CIV) and is used for evaluating unsaturated compacted fills and pavement materials.
💡 How do I select the appropriate hammer?
Use the 4.5 kg hammer for standard soils with particles less than 37.5 mm. For lower strength soils like fine-grained cohesionless or highly organic soils, use the 0.5 kg or 2.25 kg hammer. For harder materials, use the 10 kg or 20 kg hammer.
⚡ Can IV be correlated with CBR?
Yes, for the standard 4.5 kg hammer, IV can be correlated with unsoaked California Bearing Ratio (CBR) through laboratory tests. For lighter hammers, IV can be independently correlated to unsoaked CBR or used to infer percentage compaction for lower strength soils.
📌 What are the field procedures?
Three field procedures are available: Field A for IV alone, Field B for IV and water content, and Field C for IV, water content, and dry density. These allow for comprehensive field assessment of soil conditions.