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D5779 – Standard Test Method Technical Guide
📐 Scope and Field Application
ASTM D5779/D5779M defines the rapid field determination of specific gravity for rock and manmade materials used in erosion control, such as riprap. It is designed for expedient testing in quarries and work sites. The standard itself states it lacks the accuracy of the laboratory method D6473/D6473M, as there is no requirement for measuring water temperature or calculating its density. Values stated in SI or inch-pound units are separately standard.
⚠️ Field Limitations: The rapid method sacrifices precision for speed. Results are for field screening and are not a direct substitute for D6473 compliance testing. All calculated values must adhere to the significant digit rules of Practice D6026.
⚙️ Test Procedure and Equipment Overview
The simplified procedure uses a balance (per Guide D4753) and a water tank. The test specimen is weighed in air and suspended in water. The specific gravity is calculated based on Archimedes’ principle, assuming the density of water is 1.0 g/cm³. This omission of temperature correction is the primary distinction from the standard laboratory method.
| 🟦 Feature | 📏 D5779/D5779M (Field) | 📐 D6473/D6473M (Lab) |
|---|---|---|
| 🎯 Primary Use | Field QC, material sorting | Design, acceptance testing |
| ⚡ Water Density Correction | Not required | Required (from temperature) |
| 📏 Temperature Control | None specified | Required |
| 🟦 Precision Level | Lower (expedient) | Higher (controlled) |
📊 Material Significance and Results
Specific gravity is a critical property for evaluating material durability and quality for erosion control, as referenced by Practice D4992. While field results are less precise, the method provides immediate insight for material selection on site. The data allows quick identification of unsuitable lightweight or porous materials before they are placed.
💡 Practical Tip: Ensure the test specimen is representative of the overall material source. Due to the simplified procedure, variations in water temperature can introduce a small systematic bias, but the method excels at screening out grossly substandard materials during active quarry or construction operations.
| 🪨 Material Type | 📐 Typical Field SpG Range | ⚡ Typical Field Min. |
|---|---|---|
| Granite | 2.60 – 2.70 | 2.50 |
| Limestone | 2.50 – 2.65 | 2.40 |
| Basalt | 2.80 – 3.00 | 2.60 |
❓ Frequently Asked Questions
💡 Why doesn’t D5779 require measuring water temperature?
The standard is designed for expedient field use where maximum accuracy is not the primary goal. The water density is approximated at 1.0 g/cm³ to simplify the procedure, accepting the resulting loss in precision compared to the lab method D6473.
🔍 What materials can be tested?
Rock and manmade materials specifically intended for erosion control, including riprap, gabion stone, and other armor stone. The method accommodates the large, irregular specimens typical of these materials.
⚡ How does this relate to D6473?
D6473/D6473M is the official laboratory standard for specific gravity and absorption. D5779 is an acknowledged field alternative with lower accuracy. It is suitable for field screening but not for strict compliance testing without accounting for the inherent bias between the methods.
📌 What are the significant digit rules?
Section 1.5 mandates the guidelines from Practice D6026 for all observed and calculated values. Measured or calculated value(s) must be rounded to the nearest decimal or significant digit in the specified limits of the project.