WBM ROADS

WBM ROADS

Dr. B.SRIDHAR 

TYPES OF HIGHWAY CONSTRUCTION

The highways types ar e classified as below * Earth and gr ave avel roads * Soil sta bilized roads * Water bound macadam (WBM) * Bituminous roads * Cement Concr ete roads

PAVEMENT TYPES

The selection of  base cour se se and the sur fa face cour se se ollowing factor s: depends u pon the f ollo s: * Type and intensity of  tr affi affic * Funds availa ble * Subgr ade ade soil and dr ainage ainage conditions * Availa bility of  construction mater ia ials at site * Climatic conditions * Plants and equipment availa ble * Time availa ble

The highway construction project may be broadly divided in two phases

* Earthwork and and p  pr epa epar ation of  f ssubgr ade ade * Pavement structur e

WBM ROADS  

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By John Macadam Made of  crushed or brok en en aggr ega egate mechanically interlock ed ed by rolling and the voids filled with scr eening eening and binding mater ia ial with the assistance of  f wa water  Used as a Sub-base, base cour se se or sur fa face cour se se rom 10 to 7.5 cm Thick ness ness r anges anges f rom depending on the size and gr ada adation of  the aggr ega egates used

SPECIFICATIONS Type of  Cour se se aggr ega egates 

Gener ally

consists of  f ha har d var ie ieties of  crushed aggr ega egates or brok en en stones equir emen entts f or   pavemen entt laye ayer  R equ or  pavem r 

y Pro pert Pro pe rty

ase Sub-base Sub-b

se Sur fac facing Base cour se se cour se

Los ange angelles a br asio asion

60

50

40

 pact valu Im pa ct va luee

50

40

30

iness index Flak iness Fla

-

15

15

Size and grading requirements of coarse aggregate ading No. Gr ading

Size r ange,mm ange,mm

Sieve size mm %  passing the sieve by wt.

1

90 to 40

100

100

80

65-85

63

25-6 2560

40

0-15

20

0-5

80

100

63

90-100

50

30-70

40

0-15

20

0-5

63

100

50

95-100

40

35-70

20

0-10

10

0-5

2

3

63 to 40

50 to 20

SCREENINGS 

Used

to fill u p the voids in the com pacted layer of  coar se se aggr ega egates

 Non  plastic mater ia ials lik e Moorum or gr ave avel



LL

< 20%

PI

< 6%

* Portion of  mater ia ial  passing 0.075 mm < 10%

The grading requirements of screenings for  WBM constructio construction n ading Gr ading

Size of  scr eening eening

Sieve size mm

%  passing the sieve, wt

12.5

100

10.0

90-100

4.75

10-30

0.15

0-8

10.0

100

4.75

85-100

0.15

10-30

Mm A

B

12.5

10.0

Binding material 

 

ained mater ial ial is used to  pr  event r avell avelling ing of  Fine gr ained to p r event nes.. the sto tones face cour se se P.I 4 % ± 9% f or s or sur fac f or se P.I < 6 % or base base cour se

f tthe scr eenings eenings used co nsistts of  f cru sha bl  Note: If   Note: consis crusha  blee ial li avel, the her  mater ial lik e moorum or s or sof t gr avel r e is no need applly binding mater ial. ial. to app

Construction procedure Pr epa oundation f or or r eceiving the epar ation of  f f  f ou WBM cour se se  Provision of  f La Later al confinement  S pr  eading of  Coar se eading se aggr ega egates  Rolling f sscr eenings eenings  A pplication of   S pr  inkling and Grouting in  A pplication of  Binding Mater  ial ia ying ying  Setting and Dr  