Water content - University of Missouri Civil and...

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University of Missouri Civil and Environmental Engineering MEASUREMENT OF WATER CONTENT PURPOSE The purpose of this laboratory is to acquaint you with various balances used for determining weights and to teach you how to measure the water content of soil. Water content is probably the most frequently measured characteristic of soil for engineering purposes. For example, water contents are used to provide information on weight-volume relationships, to control construction of earthen fills, and to gain insight into moisture conditions in natural deposits of soil. BACKGROUND Water content (w) is defined as the weight of water (W w ) divided by the weight of solids (W s ), and is typically expressed as a percentage: (1) To measure the water content of a sample of soil, the sample is first weighed, then placed in an oven to dry, and finally reweighed. To prevent loss of soil during this process, the soil sample is placed in a suitable container. Most containers used for this purpose are constructed of a non-corroding metal and measure 1 to 3 inches in diameter and about 1 inch in height. For unusually small samples of soil, smaller containers, constructed of lightweight plastic, are sometimes used. The moisture content containers usually come with lids which can be placed over the container to minimize gain of moisture after the soil sample is removed from the oven. To determine water content, the following weights are determined: W 1 = weight of container plus moist soil W 2 = weight of container plus oven-dry soil W c = weight of container These weights are indicated in the block diagram contained in Fig. 1. Water content is calculated as follows: (2) % 100 W W w s w x = % 100 W W W W W W w c 2 2 1 s w x - - = =
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University of Missouri Civil and Environmental Engineering Water Content Measurement p2
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University of Missouri Civil and Environmental Engineering Water Content Measurement p3 EQUIPMENT AND SUPPLIES The following equipment is required: -- drying oven set at 110 ° C ± 5 ° C -- balance with resolution of 0.01 g -- moisture content containers Various types of ovens are used for drying soil samples. Ovens with forced air circulation dry the soil samples faster and therefore are preferred. Microwave ovens dry the soil samples very quickly (on the order of 3 to 10 minutes) but have not been found to produce the same results as those obtained with conventional ovens for clays with high water contents. The standard test method for moisture content by microwave drying is ASTM D4643. PROCEDURE The procedure for measuring the moisture content of soils is outlined in ASTM standard D2216, "Standard Method of Laboratory Determination of Moisture Content of Soil." Essentially the same procedure recommended in the ASTM standard will be used, with a few slight modifications: 1. Weigh a clean, dry moisture content container. Record the number imprinted on the container,
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This note was uploaded on 09/23/2011 for the course CIVIL ENGI CE 3400 taught by Professor Rosenblad during the Spring '11 term at Missouri (Mizzou).

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Water content - University of Missouri Civil and...

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