This standard specifies the method for determining the slake durability index of a rock sample, which is a measure of its resistance to weakening and disintegration resulting from cycles of wetting and drying. It is primarily used to assess the durability of weak rocks like shales and mudstones for engineering applications.
Method for determination of slake durability index of rocks
Quick Reference Values
Test drum mesh opening2.0 mm
Test drum rotation speed20 rev/min
Total initial specimen mass450 to 550 g
Number of rock lumps10
Oven drying temperature105 °C
Test cycle duration10 minutes
Key Formulas
Id2 (%) = (Wf / Wi) * 100 — Second Cycle Slake Durability Index, where Wf is the final oven-dry mass of rock retained and Wi is the initial oven-dry mass.
Practical Notes
The second cycle index (Id2) is the most commonly reported value and is used for rock classification.
This test is critical for predicting the long-term behaviour of argillaceous rocks when exposed to atmospheric conditions in slopes, tunnels, and foundations.
Ensure specimen lumps are roughly spherical and have no sharp corners to get repeatable results.