slake durability index experiment
- 1. Lab Report GIS and RS 2012-GE-56 29 LAB: 06 Statement: To determine the Slake durability index of given rock samples Designation: ASTM D 4644 Scope: This test method covers the determination of the slake durability index of a shale or other similar rock after two drying and wetting cycles with abrasion. The purpose of this lab is to access the resistance offered by a rock sample towards weakness and disintegration when subjected to standard cycles of drying and wetting. The technique itself form an important part of test to determine the weathering properties of rock when exposed on embankment and in open cast mining as well as in many other application. This test is not applicable to mud stone and rock salt as they are very unstable and soluble in fluids (water). Principle: Apparatus: Test drum Trough Motor Oven Balance Related Theory Test drum: Comprising 2mm standard mesh cylinder of unobstructed length 100mm and dia. of 140mm with solid fix base. The drum must with stand with temperature of 105°C. Drum has solid removable lid. Trough: To contain the test drum support with axis horizontal in a manner allowing free rotation. Capable of being filed with a slaking fluid such as water to level 20mm below the axis. Drum is mounted to allow 40mm un-obstructed clearance between trough and base of mesh Motor: A motor drive capable of rotating a drum at 20rpm for 10min. Oven: An oven capable of maintaining a temperature of 110°C (230°F) Balance:-A balance capable to weigh with an accuracy of 0.5g.
- 2. Lab Report GIS and RS 2012-GE-56 30 Slake:-Rock properties change with time due to processes such as exfoliation, hydration, slaking, solution, oxidation, abrasion etc. Slaking is weakening or rock due to repetition of wetting and drying. The slake durability test:-The slake durability test, first proposed by Franklin and Chandra (1972), is a test intended to assess the resistance offered by a rock sample to weakening and disintegration when subject to one (or several) cycle(s) of drying and wetting. It is a standardized measurement of the weight loss of rock lumps when repeatedly rotated through an air water interface. Effect of Porosity:-Slaking has close relation with porosity. Due to the increase in the water content in the pores, fracture develops in the rock which leads to the weathering of rocks. This mechanism seems to dominate the durability behavior of porous rock. Gamble slake durability classification Group name % weight retained after one 10min cycle ,dry weight basis % weight retained after two 10min cycle, dry weight basis Very high durability >99 >98 High durability 98-99 95-98 Medium high durability 95-98 85-95 Medium 85-95 60-85 Low 60-85 30-60 v. low <60 <30 Procedure: Place the shale fragments in the drum. Weigh, and dry in the oven for 16 h or to constant mass. Allow the shale and drum to cool at room temperature for 20 min and weigh again. Calculate the natural water content as follows: Id = × 100 Where: A= Weight of sample + weight of empty drum B=mass of drum plus oven-dried sample before the first cycle (gm) C=mass of drum (gm)
- 3. Lab Report GIS and RS 2012-GE-56 31 Mount the drum in the trough and couple to the motor. Fill the trough with distilled water at room temperature to 20mm (0.8 in.) below the drum axis. Rotate the drum at 20 rpm for a period of 10 min. Record the water temperature at the beginning and end of the run. Remove the drum from the trough immediately after the rotation period is complete and dry the drum and the sample retained in the oven for 16 h, or to constant mass. Weigh the drum and sample to obtain the oven-dried mass for the second cycle. Repeat 7.2 and 7.3. Again weigh the drum and sample to obtain a final mass. Observations & Calculations: For first cycle: Weight of sample (wet) + drum = A = 930g (sandstone) Weight of sample (wet) + drum = A = 932g (dolomite) Weight of sample (dry) +drum after 1st weathering cycle = B = 871g (sandstone) Weight of sample (dry) +drum after 1st weathering cycle = B = 926g (dolomite) Weight of empty drum = D = 432g (sandstone) Weight of empty drum = D = 434g (dolomite) ………….. (1) Id1 for sand stone = 87.8 % Id1 for dolomite = 98.79% For 2nd cycle: Weight of sample (wet) + drum = A = 930g (sandstone) Weight of sample (wet) + drum = A = 932g (dolomite) Weight of empty drum = D = 432g (sandstone) Weight of empty drum = D = 434g (dolomite) Weight of sample + drum after 2nd wetting cycle = C = 821g (sand stone) Weight of sample + drum after 2nd wetting cycle = C = 921g (dolomite) ……………(2) Id2 for sand stone = 78.11 % Id2 for dolomite = 97.7
- 4. Lab Report GIS and RS 2012-GE-56 32 Precautions: Pieces of rocks should be round as sharp edge effect mesh of drum. Same Slaking fluid should be used which is slaking the rock in field. Comments: Sand stone has medium durability as it has less porosity and no grains. This is very simple method which is used to determine the durability test in the lab and it is only use for those rocks which are weak and less soluble in the fluids which is used in the drum. References: Physical properties of rock by Bernard Amadei ASTM D 4644 Lab 06 completed