15 Bitumen Roads

8/3/2019 15 Bitumen Roads

1/31


2/31

It gives an impermeable surface. It has proved an excellent binding material. It softens when heated.


3/31

They provide smooth, durable andcomfortable road surface for traffic.

They grant water proof surface.The surface of bituminous roads is non-

slippery.They can effectively resist the adverse

effects of rain, changes in temperature andwind.


4/31

AsphaltBitumenCutback BitumenBitumen EmulsionTarRoad OilPrimers


5/31

The asphalt is a mechanical mixture of inertmineral matter like alumina, lime, silica etc.,and the asphaltic bitumen. Following arethe two categories of asphalt: NaturalAsphalt and Residual Asphalt


6/31

This variety of asphalt is obtained fromnature. It is further subdivided into twogroups namely lake asphalt and rockasphalt.


7/31

The lake asphalt is obtained from lakes atTrinidad and Bermuda (South America) atdepths varying from 3 to 60 metres. Itcontains about 40 to 70 percent of purebitumen. The water content is about 30percent. The rest part is of impurities.


8/31

The rock asphalt is obtained from rocks atSwitzerland, France etc., It contains about10 to 15 percent of pure bitumen. The restportion consists of calcareous materials. Therocks are put on the road surface after beingcrushed and heated. The road surface isthen formed by rolling.


9/31

The bitumen is a complex organic material and itoccurs either naturally or may be obtained artificiallyduring the distillation of petroleum. It is chemically ahydro-carbon. It is insoluble in water, but it

completely dissolves in carbon bisulphide. It is blackor brown in colour and it is obtained in solid or semi-solid state. It softens when heated and againsolidifies then the temperature is lowered.


10/31

When bitumen is mixed with comparativelyvolatile solvents so as to get a solutionwhich enables the application of bitumen ata considerable lower temperature, it isknown as cutback bitumen.


11/31

A bitumen emulsion is a liquid product whichis formed by mixing together molten bitumenwith hot water in presence of an emulsifyingagent in such a manner that the bitumen ismechanically broken into fine globules. Thusemulsion is composed of bitumen which issuspended in water in a very divided state.


12/31

The term road oil is used to indicate slowcuring liquid asphalt and it is described asthe petroleum distillate from which volatileand light fractions are largely removed.


13/31

A primer may be a road oil, a cutback asphaltor a low viscosity road tar. Its main function isto penetrate into the road surface and to coatthe blindage or aggregate thoroughly so thatwhen bitumen is applied, it can stick to thestone aggregates in a better way.


14/31

The tar is a brown or black bituminousmaterial with high viscosity and it is obtainedby the destructive distillation of coal,petroleum oil, shale, wood or other organicmaterials.


15/31

This variety is also known as artificialasphalt. It is obtained by the fractionaldistillation of crude petroleum oils with anasphaltic base. Such process leaves a solidsubstance in the retort. This solid substanceis the residual asphalt.


16/31

Surface Dressing Prime Coat

Tack Coat Seal Coat Grouting Premix


17/31

The term surface dressing is used to mean theapplication of a thin layer of bitumen followed

by cover material of stone chippings and thenbinding the same by rolling. If the surfacedressing is done in one coat, it is known ansingle coat treatment and if it is carried out in

two layers it is known as double coat treatment.


18/31

When a bituminous wearing surface is to beplaced on an existing untreated foundationlayer like earth, gravel etc., or on W.B.M.road surface which is an absorbent surface,it becomes necessary to apply in the initialstage a coat of low viscosity cutbackbituminous material. Such a coat is known

as prime coat.


19/31

The term tack coat is used to indicate theapplication of a small quantity of bituminousmaterial on an existing pavement that is tobe overlaid to ensure a thorough bondbetween the old and the new pavement.


20/31

The term seal coat is defined as a verythin surface treatment which is applied asa final coat in the construction of certainbituminous wearing surfaces or over anexisting bituminous pavement which hasbeen worn out.


21/31

The term grouting is used to indicate the method in

which the bitumen is introduced to the road surfaceafter the metal is placed on the road. It is alsoreferred to as grouted or penetration macadam.When the binder enters the entire depth of the road,it is called full grouting and when it enters orpenetrates only upto about half the depth, it is calledsemi-grouting.


22/31

As the term implies, the premix is the methodof constructing a bituminous road in whichthe aggregates are coated with binder inspecial mixers before being placed on theroad surface. Thus the premix method makesit possible to coat each and every individualaggregate with uniform thickness of binder

film.


23/31

Breaking of stones Economical use of binder

Increased stability Quality control Speed in Construction.


24/31

Bitumen Bound Macadam Bituminous Carpet

Bituminous Concrete Sheet Asphalt Mastic Ashalt


25/31

Preparation of Existing Layer

Application of Tack Coat Preparation of Premix Placing the Mix on Road Surface Rolling


26/31

Preparation of the base course Application of tack coat or prime coat Preparation and placing of premix Application of seal coat


27/31

Preparation of the existing base courselayer

Preparation and placing of premix Rolling Finishing


28/31

The sheet asphalt is a mixture of wellgraded sand, bitumen and mineral filler,carefully proportioned and mixed hot toproduce a high quality surface or wearingcourse. This type of surface is usuallyplaced to a depth of 25mm to 37 mm. Itgives a dense, smooth, and impervious

surface since the material used is sand.


29/31

The term mastic asphalt is used to indicatea mixture of bitumen, fine aggregates andfiller in suitable proportion to give a voidlessand impermeable mass.


30/31

It can absorb vibrations. It forms voidless hard layer without compaction and

hence, rolling is not necessary. It is a suitable surfacing material for bridge deck slabs.

It is to be spread at a temperature of about 200 degreecelsius to a thickness varying from 25mm to 50mm. It possesses the quality of self healing of cracks without

bleeding. When cooled, the mastic asphalt results in a hard, stable

and durable layer which can easily withstand heavytraffic.


31/31

Documents

15 Bitumen Roads