Problems Associated with Bituminous Binders and Macadam Asphalt Mat

“PROBLEMS ASSOCIATED WITH BITUMINOUS

BINDERS”

1.) The thickness of asphalt film in the pavement, ranges from .005 to .010mm. Test results showed that the thicker the asphalt film, the lesser is the process of aging. Where pavement has lower percentage of voids, aging is also relatively low.

2.)Mixtures are too dry, cracks and breaks easily.

4.) Improper construction procedures can age prematurely. One example is mixing asphalt with an overheated aggregate.

6.) Climatic conditions can seriously affect the behavior of asphalt penetration.

8.) An asphalt meeting a specified penetration requirement at 77°F but with high viscosity temperature ratio will become hard and brittle at lower temperature.

7.) Different brand or source has variability in behavior. The viscosity of some asphalt varies with temperature from that of the others.

BITUMINOUS PAVEMENT

Asphalt MacadamMasticAsphalt SheetRoad MixOil Mat

Asphalt ConcreteNational PavingPlant MixArmor coat

“ASPHALT ROAD is virtually a BITUMINOUS ROAD”

“Qualities of Asphalt Road”

VISCOUS ASPHALT BINDER IS HEATED TO A FLUID CONDITION AND MIXED WITH HEATED AGGREGATES. THE MIXTURE IS THEN LAID

AND COMPACTED WHILE STILL HOT.

1.) The surface must be free from cracks or traveling due to shrinkage and fatigue failure.

2.) It must withstand weather condition including the effect of surface water, heat, cold and oxidation.

3.) It must be resistant to internal moisture such as water vapor.

4.) It must posses a tight or porous impermeable surface as the case may be suited to underlying base on sub-base.

5.) It must be smooth riding and skid free surface.

Bituminous Pavement Failure

Repetitious application of excessive load will roughen and crack the road pavement that ultimately result to complete failure of the

road way.

Repeated heavy wheel load on highly resilient soil causes deflection leading to fatigue failure of the asphalt surface.

Bituminous pavement failures are caused by excessive load.

Macadam Asphalt Mat

Macadam is a type of road construction pioneered by Scottish engineer John

Loudon McAdam around 1820. The method simplified what had been

considered state of the art at that point. Single-sized aggregate layers of small

stones, with a coating of binder as a cementing agent, are mixed in an open-structured roadway.

MACADAM ASPHALT MAT

Constructing the Macadam Asphalt Road

1.) Spread the coarsest aggregate to the roadway. Compact with either smooth wheeled roller or vibratory devices.

2.) Smoothness of the surface is checked after compaction. Low spots are corrected by removing, replacing and recompacting the stones until smooth surface is attained.

3.) Apply asphalt by spreading the right amount of bitumen at specified temperature. The lower the stone layer will not be coated if the asphalt binder is too thick On the other hand, too fluid mixture will cause running the binder down underlying layers

4.) In placing the keystone base course, sufficient amount of smaller stone is mixed and spread on top to fill the interlocking voids, followed by compaction the spraying with asphalt binder.

5.) Sealing of the surface is applied to seal the pavement against moisture. These involve spreading of selected binder, spraying and rolling of the cover aggregates.

6.) During construction , the weather must be dry and warm. If not, it is better to used emulsified asphalt as binder.

7.) Before the application of asphalt binder, coarse aggregate is first chocked with smaller stone to seal the remaining top voids, followed by spraying emulsified asphalt binder

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