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DENSITY TESTS - 14070_271

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Figure  13-4.—Sand-displacement  method  apparatus. required that 98 percent of the maximum density be not within the specified range, additional rolling may be obtained  through  compaction.  The  maximum  attainable was 127.2 pcf; 98 percent of this is 124.7 pcf. The dotted line is drawn at the 124.7 pcf level. Any moisture content lying in the crosshatched area above this line would produce the specified density for a given compactive effort;  therefore,  the  range  of  permissible  moisture content is from 9 to 13 percent. DENSITY TESTS From  the  preceding  discussion,  you  know  that compaction testing is performed to determine the OMC and the maximum density that can be obtained for a given  soil  at  a  given  compactive  effort.  You  also  know that, using the maximum density, you can determine a range of densities and moisture contents that will satisfy the  compaction  requirements  for  a  project.  During  the construction of that project, however, a control must be in place to measure whether or not the compaction requirements  have  been  met.  That  control  is  density testing. If the results of the density test determine that the  compaction  process  has  produced  a  density  within the range specified, then the compaction is complete. On the other hand, if the test results reflect densities that are necessary  or  the  moisture  content  may  have  to  be adjusted. Several different methods are used to determine the in-place density of a soil; however, the methods that EAs are most apt to use are the sand-displacement method and the nuclear  moisture-density  meter  method. Sand-Displacement   Method A  full  discussion  of  the  procedures  used  in  the sand-displacement  method  can  be  found  in  Test  Method for  Pavement  Subgrade,  Subbase,  and  Base-Course Material, MIL-STD-621A, and in NAVFAC MO-330. This method, often called the  sand-cone method,  may be  used  for  both  fine-grained  and  coarse-grained materials. In general, the test consists of digging out a sample of the material to be tested, using calibrated sand to determine the volume of the hole from which the sample was removed and to determine the dry unit weight of the sample. EQUIPMENT  AND  TOOLS.—  The  essential equipment and tools that you test are shown in figure 13-4. will need to perform the In addition to these, you 13-5



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