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Slake Durability Index Calculator

Calculate slake durability index (Id1, Id2) from mass loss over two wetting-drying cycles per ISRM / ASTM D4644. Includes durability classification.

Last updated 28 July 2026

About this tool

Calculate the Slake Durability Index from mass retained after one and two wetting-drying cycles per ISRM Suggested Methods / ASTM D4644. Results are classified from very low (<30%) to very high (>98%) durability.

How to use this tool

Enter original dry mass and dry mass after each cycle

Technical information

Id = (retained mass / original mass) × 100

Limitations

Standard test uses 10 rock pieces of 40-60g each, two 10-minute cycles in a rotating mesh drum. Results are sensitive to sample selection and initial moisture state.

Revision history

28 July 2026: Initial release

Disclaimer

This tool is provided for educational and general information purposes only. It is not a substitute for professional engineering advice, design or verification.

Diggy and its contributors are not licensed engineering consultants and no results generated by this tool should be used directly for construction, design or safety-critical decisions.

All values and outputs are based on published empirical correlations and should be independently checked and confirmed by a qualified geotechnical engineer before use.

By using this tool, you accept full responsibility for how you interpret and apply the information provided.

Spotted an error? Let us know.

Original dry mass (g)

Dry mass after cycle 1 (g)

Dry mass after cycle 2 (g)

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