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Pavements

Pavements. Concrete. Concrete Rigid pavement Used where strength is an issue Runways, interstates and major roads Continuous reinforcing Must have a good base and joints and cracks must be sealed Long life – 50 years Major rehab is a major problem. Concrete. Forming and pouring

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Pavements

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  1. Pavements

  2. Concrete • Concrete • Rigid pavement • Used where strength is an issue • Runways, interstates and major roads • Continuous reinforcing • Must have a good base and joints and cracks must be sealed • Long life – 50 years • Major rehab is a major problem

  3. Concrete • Forming and pouring • Old way – set forms and have equipment ride the forms • Paving train – mix, place, finish, cure all in one train of equip • Standard forms 10 ft long 8 – 12 inches deep • New Way • Slip form, Use 0 slump concrete • Machine pulls form with it slab comes out finished • F 8-1, 8-2

  4. Concrete • Roller Compacted Concrete • Dam construction, landfills • 0 slump concrete is placed on a site and compacted w/vibratory roller • Higher strength, low air entrainment

  5. Asphalt • Bituminous • Bituminous distributor • F8-4 • Used on all types of bituminous construction • Application rate depends on spray bar length, travel speed, pump output • Control by bitumeter • S = (9xP)/(WxR) • S= road speed, P = pump output, W= spraybar width, R= application rate

  6. Asphalt • Surface treatments • Prime coat – goes on unpaved surface • Provides waterproofing and wear surface • 0.25 – 0.5 gal/sq. yd.- cures in 24 – 48 hours • Tack coat – goes on a paved surface to act as bonding agent • 0.1 gal/sy – quick cure • Dust pallitive – keeps dust down for 30 days • Fog seal – slow setting, 1-3 parts water • Emulsion slurry sealer – driveway sealer • Sand seal – fine aggregates and asphalt

  7. Asphalt • Single pass treatments • Spray bitumin • Cover with aggregate 1 stone deep • 25 – 30 # of aggregrate/sy • 0.25- 0.3 gal/sy binder • Sweep surface • Apply prime coat, cure • Apply binder • Apply aggregate • Roll surface • Sweep to remove loose stone

  8. Asphalt • Multi pass treatments • Spray bitumin • Multiple single pass treatments • 25 – 30 # of aggregrate/sy • 0.25- 0.3 gal/sy binder • Each layer’s aggregate is ½ size of previous layer

  9. Asphalt • Asphalt Paving • Hot mix – high type pavements • Cold mix – patching • Penetration macadam – old way of paving • Place and compact 4” of coarse aggregate • Cover with asphalt binder and a smaller aggregate (key aggregate) and rolled • Cover with asphalt binder and a smaller aggregate (key aggregate) and rolled

  10. Asphalt • Road Mix • Mixed on roadway • Grader, rotary mixer, travel plants • Hard to get a consistent result

  11. Asphalt • Hot Mix (HMA) –highest form of asphalt pavement • Can be used as soon as compacted and cooled to ambient temp • Flexible, frost resistant • Cold mix – like hot mix • Advantages – can haul long distances, stockpile, • Disadvantages – slow curing, low initial stability, difficult to compact in cold weather

  12. Asphalt • Hot mix paving operations • Delivery of asphalt mix,spreading and compaction • Spreader couples with the delivery truck and pushes it along as asphalt is unloaded • Spreader spreads and compacts • Spreader consists of pusher unit and screed unit • Spreaders control depth and width of pavement using laser, stringline, shoe to control screed elevation

  13. Asphalt • Towed pavers – smaller jobs – usually driveways • Max width 10 ft • Large paver • To lay a 3” deep, 12 ft wide, strip at 50 ft/min need 600 tons/hr of asphalt

  14. Asphalt • Compacting immediately after spreading • Breakdown rolling – provides initial compaction - static steel rollers with drive wheel forward • Intermediate rolling – pneumatic rollers – better surface sealing • Finish rolling – tandem steel rollers – final compaction

  15. Asphalt • Superpave • Developed due to asphalt concrete failures • Uses lower asphalt content ,crushed stone and optimizes for local conditions- NYS thruway uses 7 different mixes

  16. Repair and Rehab • Highways • Resurface, restoration, rehabilitation and reconstruction – 4Rs • Resurfacing surface treatments, overlays, • Restoration and Rehab – return highway to acceptable condition • Planning or milling top layer , fixing lower level, repave • Reconstruction – complete redo of roadway

  17. Repair and Rehab • Recycling pavement • Concrete is broken up and sent to a recycling plant which removes steel and crushes concrete into aggregate • Asphalt is milled and recycled in an asphalt plant F- 8-10&8-11 • HMWK Ch 7 # 2,3,9 Ch 8 # 5,7,9

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