Slake durability test complete procedure

Determining Slake Durability Index of Rocks

Objective

This test aims to measure how well a rock sample withstands weakening and breaking apart when subjected to two alternate cycles of drying and wetting in water.

Reference standards

IS- 10050:1981

Equipment Needed

1. Balance

• Capacity: As required for sample weight
• Accuracy: 0.01% of the sample weight

2. Slake Durability Test Apparatus

• Speed: Must rotate at 20 revolutions per minute (rev/min)

Figure 1 Source: https://www.mdpi.com/

Slake Durability Test Apparatus

                                            

3. Oven

• Temperature: 105 ± 5°C and capable of maintaining it for at least 12 hours.
• Accuracy: ± 1°C

Electric oven 

Sample Preparation

1. Prepare a sample consisting of at least 10 rock pieces.

2. Each rock piece should weigh between 40 to 60 grams.

3. The total weight of the sample should be between 400 to 600 grams.

4. Ensure the rock pieces are roughly spherical with rounded edges.

Procedure

1. Dry the Sample:

• Place the rock pieces in the oven set at 105 ± 5°C.
• Dry the sample until it reaches a constant weight.

2. Weigh the Sample:

• Place the dried rock pieces in the drum of the slake durability test apparatus.
• Weigh the drum with the sample and record this weight as ‘A’.

3. Initial Rotation/ First cycle:

• Attach the lid to the drum and place it in the trough.
• Fill the trough with water so that the water level is 20 mm below the drum's axis.
• Rotate the drum at 20 rev/min for 10 minutes.

4. Weigh After First Cycle:

• Remove the drum from the trough and take off the lid.
• Dry the drum and the remaining rock pieces in the oven at 105 ± 5°C.
• Weigh the drum with the remaining rock pieces and record this weight as ‘B’.

5. Second Rotation/ Second cycle:

• Repeat steps 3 and 4 for another 10 minutes.
• Weigh the drum with the remaining rock pieces again and record this weight as ‘C’.

6. Final Weighing:

• Clean the drum and weigh it empty.
• Record this weight as ‘D’.

Calculation

• Calculate the Slake Durability Index (Id2) using the following formula:
• Slake Durability Index (Id2) = (C−D/A−D) ×100

 

Slake Durability Index value 

     

Reporting

• Report the Slake Durability Index to the nearest 0.1%.
• Generally tap water at 20oC is used as slaking fluid.

Reference:  IS- 10050:1981,IS 9179:1979, ISRM, MDPI