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D5148-10 – Standard Test Method Technical Guide
🧪 Test Overview and Scope
The Centrifuge Kerosine Equivalent (CKE) test, designated under ASTM D5148-10, is a fundamental method for characterizing the surface properties and absorptive behavior of aggregates intended for use in bituminous mixtures. This standardized procedure supports the calculation of an aggregate’s surface area and its affinity for liquid hydrocarbons, providing critical data for mix design and quality control.
Scope and Units: This test method applies to both coarse and fine aggregate fractions. Standard values are detailed in inch-pound units, with SI unit conversions provided in parentheses for informational context. An important exception exists for mass measurements, where grams remain the standard unit to maintain the practical precision of the original test design. Regarding sieves, SI units are standard for wire cloth openings, while inch-pound units remain standard for the sieve frames.
🏗️ Aggregate Fractions and K-Factor Terminology
ASTM D5148-10 establishes precise definitions for the aggregate fractions involved in the CKE determination. The coarse fraction (C) is retained on the 4.75 mm (No. 4) sieve after passing the 9.5 mm (⅜ in.) sieve. The fine fraction (F) passes the 4.75 mm (No. 4) sieve. The resulting K-factors are central to the test’s calculations.
| 🧩 Fraction | 📏 Sieve Passing | 📐 Sieve Retained | 🎯 K-Factor |
|---|---|---|---|
| Coarse (C) | 9.5 mm (⅜ in.) | 4.75 mm (No. 4) | Kc |
| Fine (F) | 4.75 mm (No. 4) | Pan | Kf |
| Composite | — | — | Km |
Kc reflects the coarse aggregate’s properties via SAE No. 10 oil retention, while Kf accounts for the fine aggregate’s behavior using kerosine retained, based on computed surface area and percent passing the No. 4 sieve. The Km factor represents the composite “mean” value for the total aggregate blend.
💡 Technical Note on Oil Substitution: Based on comparative testing recognized within the standard, SAE No. 10 oil may be substituted with Shell Tellus No. 100 oil for determining the Kc factor without compromising the accuracy of the results. Always verify the equivalence against your specific material set.
⚙️ Key Apparatus and Referenced Standards
A compliant CKE test requires strict adherence to several supporting ASTM standards for sampling, sample reduction, and laboratory apparatus. The table below summarizes the critical standards referenced within D5148-10.
| 🔖 Standard | 📄 Title |
|---|---|
| D75 | Practice for Sampling Aggregates |
| C702 | Practice for Reducing Samples of Aggregate to Testing Size |
| E11 | Specification for Woven Wire Test Sieve Cloth and Test Sieves |
| D4753 | Guide for Evaluating, Selecting, and Specifying Balances |
| D3666 | Specification for Minimum Requirements for Agencies Testing and Inspecting Road and Paving Materials |
| E832 | Specification for Laboratory Filter Papers |
⚠️ Safety and Compliance Advisory: This standard does not purport to address all safety concerns, if any, associated with its use. It is the responsibility of the user to establish safe handling practices for kerosine and test oils, referencing Section 7.1 of the full standard for specific hazard statements. Testing agencies must also comply with Specification D3666 for minimum personnel and quality system requirements.
❓ Frequently Asked Questions
🔍 What is the primary purpose of the Centrifuge Kerosine Equivalent test?
The CKE test determines the relative hydrocarbon absorption and surface roughness of aggregates. It is a pivotal tool in the design of bituminous mixtures, helping to forecast the binder demand of the aggregate blend and to identify highly absorptive or dusty aggregates that could cause premature pavement durability issues.
💡 Can I substitute SAE No. 10 oil with another standard oil for the Kc factor?
Yes. Note 1 of ASTM D5148-10 explicitly states that, based on comparative testing in California, Shell Tellus No. 100 oil can be used as an effective substitute for SAE No. 10 oil with equivalent results when determining the Kc factor.
⚡ What are the standard sieve sizes defining the coarse aggregate fraction for this test?
The coarse fraction (C) for this test is definitively the portion of the sample which passes the 9.5 mm (⅜ in.) sieve and is retained on the 4.75 mm (No. 4) sieve. The fine fraction (F) is the portion which passes the 4.75 mm (No. 4) sieve.
📌 How does the Kc factor differ from the Kf and Km factors?
Kc is based on the percent of SAE No. 10 oil retained by the coarse fraction, capturing its absorption and surface roughness. Kf is derived from the kerosine retained by the fine fraction, accounting for surface area and absorption. Km is the calculated composite “mean” value representing the combined effect of the coarse and fine materials in the full aggregate blend.