Figure 13-4.—Sand-displacement method apparatus.required that 98 percent of the maximum density benot within the specified range, additional rolling may beobtained through compaction. The maximum attainablewas 127.2 pcf; 98 percent of this is 124.7 pcf. The dottedline is drawn at the 124.7 pcf level. Any moisture contentlying in the crosshatched area above this line wouldproduce the specified density for a given compactiveeffort; therefore, the range of permissible moisturecontent is from 9 to 13 percent.DENSITY TESTSFrom the preceding discussion, you know thatcompaction testing is performed to determine the OMCand the maximum density that can be obtained for agiven soil at a given compactive effort. You also knowthat, using the maximum density, you can determine arange of densities and moisture contents that will satisfythe compaction requirements for a project. During theconstruction of that project, however, a control must bein place to measure whether or not the compactionrequirements have been met. That control is densitytesting. If the results of the density test determine thatthe compaction process has produced a density withinthe range specified, then the compaction is complete. Onthe other hand, if the test results reflect densities that arenecessary or the moisture content may have to beadjusted.Several different methods are used to determine thein-place density of a soil; however, the methods that EAsare most apt to use are the sand-displacement methodand the nuclear moisture-density meter method.Sand-Displacement MethodA full discussion of the procedures used in thesand-displacement method can be found in Test Methodfor Pavement Subgrade, Subbase, and Base-CourseMaterial, MIL-STD-621A, and in NAVFAC MO-330.This method, often called the sand-cone method, maybe used for both fine-grained and coarse-grainedmaterials. In general, the test consists of digging out asample of the material to be tested, using calibrated sandto determine the volume of the hole from which thesample was removed and to determine the dry unitweight of the sample.EQUIPMENT AND TOOLS.— The essentialequipment and tools that youtest are shown in figure 13-4.will need to perform theIn addition to these, you13-5
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