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Figure 15-66.Longitudinal drainage of runways.
Chapter 16 Paving Operations and Equipment

Equipment Operator Basic - Beginning construction equipment operators manual
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GRADING  AND  EXCAVATING Grading and excavating are cutting the high spots to grade and filling in the low spots. In cutting down the high spots, enough suitable fill material may be removed  to  fill  in  low  spots.  However,  it  may  be necessary to develop other sources of fill material. If the site is on hard and rocky terrain, loosen and break the soil with a dozer ripper. Before fill material can be placed  in  low  spots,  a  suitable  foundation  must  be prepared. Material of a low-bearing capacity may have to be dug up before the fill is placed. Base  Course The base  course distributes wheel load stresses from  the  surface  pavement  to  the  subgrade.  Since stresses in the base course are more concentrated than in the subgrade, the base course Placement  and  Compaction When placing and spreading on a prepared subgrade, start at must be stronger. base  course  materials the point nearest the 15-42 source or at the point farthest from the source. Then place  the  material  progressively  away  from  or  toward the source, respectively. The advantage of working from  the  point  nearest  the  source  is  that  hauling equipment can be routed over the spread material, which  helps  compact  the  base  course  and  avoids cutting  up  the  subgrade.  An  advantage  of  working from the point farthest from the source is that the hauling equipment further compacts the subgrade, reveals any weak spots in the subgrade, and interferes less  with  the  movement  of  spreading  and  compaction equipment. Base   course   compaction   must   produce   a uniformly  dense  layer,  conforming  in  every  way  to specification requirements. The thickness of the lifts should NOT exceed that which can be compacted to the  required  density.  The  thickness  of  the  lifts  is determined  by  the  size  of  the  compaction  equipment, such as 6 inches for rollers and 3 inches or less when using  tampers. NOTE:  Optimum   moisture   content   must   be maintained  during  compaction.







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