Using a heating plate or other apparatus can be used to heat the pycnometer. Entrapped Air Removal: deairing of the water and soil slurry may be accomplished by boiling, application of a partial vacuum, or both.Full-immersion thermometers are not permitted. Thermometric Device: the thermometer must have readability to 0.1☌ with an accuracy of ☐.5☌ and be standardized to a NIST traceable device.Group image of 250ml, 500ml, and (unnamed) stoppered flasks. A minimum capacity of 250ml is specified, and a 500ml capacity flask is sometimes required. The stopper physically controls the water volume of stoppered flasks. Volumetric flasks are typically used but require careful adjustment of water to the calibration mark. Pycnometers: the test method permits the use of a volumetric flask or iodine flasks with a stopper.Table Resource: Specific Gravity Lab Equipment and Apparatus This blog post will focus on the equipment and procedures used to perform the ASTM/AASHTO method. Reliable test results depend on strict adherence to the practices and techniques outlined. Practitioners should be aware of the significant differences between the test methods. While the equipment required is not sophisticated, the procedures are extensive and meticulous, and performing the test by the book can be a challenge. As with any laboratory test, these methods require attention to detail but are easy to perform correctly and do not require much in the way of specialized techniques or equipment.ĪSTM D854, and the identical AASHTO T 100, Standard Test Methods for Specific Gravity of Soil Solids by Water Pycnometer, focus on producing measurements with a high degree of precision. Army Corps of Engineers laboratory soils testing manual, and some state DOTs are often considered adequate for basic applications. Standard test methods described in the U.S. Traditional methods for determining specific gravity are straightforward. Applications include the foundation design for structures, calculations for the stability of soil embankments, and estimations of settlement for engineered soil fills. This dimensionless unit is the ratio of material density to the density of water and is used to calculate soil density, void ratio, saturation, and other soil properties. Specific gravity is a fundamental property of soils and other construction materials. To better understand how the Specific Gravity is calculated, the aforementioned measured quantities are presented in Figure 1.įigure 1: The measured weights needed to derive the specific gravity (G S) of a soil.īased on the temperature of the water that was recorded in the last step, the density of the distilled water ρ w is derived through specific tables (i.e., ρ w=998.Importance of Specific Gravity of Soil Solids Use the thermometer to derive the temperature of the water.Remove the vacuum, clean and dry the flask and add distilled water up to the mark.The procedure should last for about 2-3 minutes for sands and 10-15 minutes for clays. Use a vacuum pump to gradually apply vacuum and remove the entrapped air while spinning the flask to remove the air bubbles.Fill around 2/3 of the flask with distilled water.Use the funnel to carefully place the soil into the flask and weigh it ( W 3).Weigh around 50 grams of soil material.Clean and dry the inside (above the water level) and the outer part of the flask and weigh it ( W 2).Fill the flask with distilled water up to the graduation mark.Weigh the empty and clean volumetric flask ( W 1).The procedure that is followed towards that goal is the following: The Specific Gravity is computed as the ratio of the weight in air of a given volume of soil particles at a stated temperature to the weight in air of an equal volume of distilled water at the same temperature. Volumetric flask marked with a thin ring at a specific point of its neck (graduation mark).To derive the Specific Gravity of a soil, the following equipment is needed: It is also used to derive several important soil parameters such as the porosity, the dry and saturated density and the degree of saturation. G S is a significant parameter of soil mechanics since it can be associated with the soil’s mineral composition and weathering. G S should not be confused with the soil density since it is a dimensionless unit and expresses the ratio of two particular densities. Soil is a three-phase material that consists of solid particles and voids which are filled with water and air. The specific gravity (G S) of a soil refers to the ratio of the solid particles’ unit weight to the unit weight of water.
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