figure 15-27, three tests (called runs) were made, usingcans numbered 5, 10, and 1. Online D (weight of tare),record the weight of each can. Note that although thecans are identical in appearance, they vary slightly inweight. Online A (weight of tare and wet soil), recordthe weight of each can with wet contents. On line B(weight of tare and dry soil), record the weight of eachcan with contents after drying.Online C, Ww (weight of water in the soil sample)was obtained by subtracting (B) from (A). On line E,Ws (weight of dry soil) was obtained by subtracting (D)from (B).The line labeled “water content, w,” shows theresults obtained by substituting the known values in thefollowing formula:The average of these three values, or 12.7 percent, is thevalue of w (percentage of moisture content) for thesample.Calcium Carbide Gas Pressure MethodThis method uses a 26-g SPEEDY MOISTURETESTER to determine the moisture content of soils, fineaggregates, sand, and clay. By using the SPEEDYtester, the moisture content can be determined in thelaboratory or field in from 45 sec to 3 rein, dependingupon the material being tested. The tester operates onthe principle of a calcium carbide reagent (reactiveagent) being introduced into the free moisture of the soilsample. The resulting chemical reaction creates a gasthat is contained in a sealed chamber, the pressure ofwhich can be measured with the built-in gas pressuregauge.APPARATUS.— The SPEEDY moisture test set(fig. 15-28) includes the SPEEDY tester, a balance,half-weight reagent, measuring scoop, brushes,cleaning cloth, and two 1 1/4-in. steel balls.PROCEDURE.— The procedure for determiningmoisture content using the SPEEDY MOISTURETESTER is as follows:1. Weigh a 26-g sample of soil.2. Place the soil sample and two 1 1/4-in. steel ballsin the large chamber.FIGURE REMOVEDCopyright permission not grantedfor electronic media.Figure 15-28.—SPEEDY moisture test set.15-20
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