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Figure 16-17.-Corrugations.
Repairing Defective Flexible Pavements

Equipment Operator Basic - Beginning construction equipment operators manual
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subgrade. Upheaval may also be caused by the swelling effect of moisture on expansive soils. Disintegration Disintegration is the breaking up of a pavement into small, loose fragments. This includes the dislodging of aggregate  particles.  If  not  stopped  in  its  early  stages, disintegration  can  progress  until  the  pavement  requires complete  rebuilding.  Potholes  and  raveling  are  two  of the more common types of early stage disintegration. POTHOLES.— Potholes are bowl-shaped holes of  various  sizes  in  the  pavement,  resulting  from localized  disintegration  under  traffic  (fig.  16-21). They are usually caused by weakness in the pavement, resulting from too little binder, too thin a surface, too many  fines,  or  poor  drainage. RAVELING.—  Raveling is the progressive loss of surface material by weathering or traffic abrasion (fig. 16-22). Usually the fine aggregate wears away first,   leaving   little   pockmarks   in   the   pavement surface. As  erosion  continues,  larger  particles eventually break free, and the pavement soon has the rough  and  jagged  appearance,  typical  of  surface erosion. Raveling  is  caused  by  poor  construction methods, inferior aggregates, or poor mix design. Slippery Surfaces One  of  the  most  common  causes  of  a  slippery flexible pavement is a thin film of water over a smooth surface. his can cause a vehicle to hydroplane. Other causes of slippery surface in flexible pavements are bleeding  and  polished  aggregates. Figure  16-21.-Pothole. Figure 16-22.—Raveling. BLEEDING AGGREGATES.— Bleeding is the upward   movement   of   bituminous   material   in   a flexible pavement, resulting in the formation of a film of  bituminous  material  on  the  surface  (fig.  16-23). The  most  common  cause  of  bleeding  is  too  much asphalt in one or more of the pavement layers. This is usually the result of a rich plant mix or a prime or tack  coat  that  is  too  heavy.  Bleeding  normally  occurs in  hot  weather. POLISHED AGGREGATES.—  Polished   aggre- gates are those that have been worn smooth under traffic (fig. 16-24). Polished aggregates are caused by using the wrong type of aggregate in the pavement mix. Figure 16-23.-Bleeding asphalt. 16-20







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