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Unformatted text preview: lculate the hygroscopic moisture correction factor by: a. First calculate the hygroscopic moisture content: 100 where: Mw = mass of water (g) Ms = mass of oven dried soil (g) = hygroscopic moisture content (%) b. Then calculate hygroscopic moisture correction factor: where: Ms = mass of oven dried soil (g) Mad = mass of air dried soil (g) Hcf = hygroscopic correction factor Hcf *Refer to Table 1 for calculating the above. Hydrometer Calibration/Composite Correction Before starting a hydrometer test, three things need to be determined. The first thing needing correction is from the fact that a dispersing agent has higher specific gravity than the distilled water; this difference is accounted for when using the equations for percentage of soil remaining in suspension. Second, the hydrometer itself has been calibrated at 20°C and during the test the temperature of the liquid (soil/water mixture) will vary, and third is the hydrometers have been graduated by the manufacturer to be read at the bottom, and since this is not possible due to the soil particles in suspension, readings are taken at the top of the meniscus, and then corrected. The following steps are the procedure on how to determine the composite correction. Winter 2013 6 CIVE 153 – Earth Engineering Hydrometer Analysis Department of
Engineering 1. Prepare a 1000ml liquid in the control cylinder composed of 125mL of dispersing agent and distilled water filled to the mark on the control cylinder. 2. Allow the temperature of the liquid to become equilibrium with the temperature of the lab. 3. Place the hydrometer in the liquid; allow it to adjust to the temperature and to stop moving. 4. Read the hydrometer at the TOP of the meniscus formed on the stem. a. A reading less than zero is recorded as a negative (‐) correction and a reading between zero and sixty are recorded as a positive (+) correction. 5. For a 152H hydrometer, the difference between the reading observed and zero is the composite cor...
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This document was uploaded on 03/30/2014 for the course CIVE 153 at Waterloo.
- Winter '13