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D5918-13 – Standard Test Method Technical Guide
📐 Test Principles and Specimen Preparation
ASTM D5918-13 provides laboratory test methods for assessing the frost heave and thaw weakening susceptibilities of soils, primarily for use in pavement systems. The test is designed for soils where particle size criteria, such as the 3% finer than 20 mm limit in Specification D2940, are inconclusive. Specimens should be prepared and tested in quadruplicate for reliability, with automated temperature control and data logging recommended.
| 🟦 Aspect | 📏 Requirement |
|---|---|
| Particle size threshold | 3% finer than 20 mm (D2940) |
| Number of specimens | 4 (suggested) |
| Temperature control | Manual or automated |
| Data acquisition | Automated preferred |
⚙️ Test Procedure and Measurements
The test procedure involves two phases: freezing and thawing. During the freezing phase, the frost heave rate is measured. After thawing, the bearing ratio is determined using Test Method D1883. The frost heave susceptibility is derived from the heave rate, and the thaw weakening susceptibility from the bearing ratio. These index values are compared with classification systems, such as those used by the Corps of Engineers, to categorize the soil.
⚠️ Important: This test method is an index test and cannot predict actual field heave or post-thaw strength; it is not valid for permafrost or refrigerated structure foundations.
📊 Units and Data Precision
The standard mandates the use of SI units as standard, with inch-pound units in parentheses for reference. The gravitational system is used, where pound (lbf) represents force and mass is in slugs, though the slug is not explicitly used unless dynamic calculations are involved. All recorded values must follow the significant digits and rounding practices defined in Practice D6026.
| 🟦 Quantity | 📏 SI Unit | 📐 Inch-Pound Unit |
|---|---|---|
| Force | N (newton) | lbf (pound-force) |
| Heave Rate | mm/h | in/h |
| Bearing Ratio | % CBR | % CBR |
| Mass | kg | slug (not used unless dynamic) |
© 2026 TNLab — This article is a technical interpretation for reference only. The original standard as published by ASTM International takes precedence.