The document describes the layers of a conventional flexible pavement, including: 1. The surface course is the top asphalt layer that must withstand wear from traffic. 2. Beneath is the binder course, which can be thicker than the surface course and uses larger aggregates. 3. Below are additional layers like the base course, subbase course, and compacted subgrade, with the subgrade being the native soil. 4. These layered systems use better materials at the top and inferior materials at the bottom to efficiently distribute loads to the subgrade.

1. Pavement Types- Flexible pavement –
Cross section
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Subgrade
Base Coarse
BBC
BWC

2. Flexible Pavement Types
1- Conventional Flexible Pavement. ‫الرصفة‬
‫التقليدية‬ ‫اإلسفلتية‬
‫من‬ ‫النوع‬ ‫هذا‬
‫الرصفة‬
ً‫مهندس‬ ‫جمعٌة‬ ‫طورته‬
‫األمرٌكٌة‬ ‫والمواصالت‬ ‫الطرق‬
AASHTO
‫تتكون‬ ‫حٌث‬
‫الرصفة‬
‫رئٌسٌة‬ ‫طبقات‬ ‫ثالث‬ ‫من‬
‫على‬ ‫القدرة‬ ‫حٌث‬ ‫من‬ ‫مواد‬ ‫نوعٌة‬ ‫أفضل‬ ‫وتكون‬
‫أو‬ ‫السطح‬ ‫طبقة‬ ‫وتسمى‬ ‫العلٌا‬ ‫الطبقة‬ ً‫ف‬ ‫التحمل‬
‫اإلسفلتٌة‬ ‫الطبقة‬
SURFACE COURSE
‫األساس‬ ‫طبقة‬ ‫تلٌها‬
BASE COURSE
‫ثم‬
‫األساس‬ ‫تحت‬ ‫ما‬ ‫طبقة‬
SUBBASE COURSE
‫هذه‬ ‫خالل‬ ‫من‬ ‫المرورٌة‬ ‫الحموالت‬ ‫تأثٌر‬ ‫نقل‬ ‫وٌتم‬
‫قدرتها‬ ‫تكون‬ ‫أن‬ ‫ٌفترض‬ ً‫الت‬ ‫التربة‬ ‫إلى‬ ‫الطبقات‬
‫ٌجري‬ ‫ما‬ ‫وغالبا‬ ‫نسبٌا‬ ‫عالٌة‬ ‫التحمل‬ ‫على‬
‫دمكها‬
COMPACTED SUBGRADE
‫مواصفاتها‬ ‫لتحسٌن‬
.
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3. Conventional Flexible Pavement
 Are layered systems with:
 better materials on top where the intensity of stress is high and
 inferior materials at the bottom where the intensity is low.
 A structure that;
 maintains intimate contact with sub grade and
 distribute loads to sub grade , and depends on
 aggregate interlock,
 particle friction, and
 cohesion for stability.
 Adherence to this design principle makes the use of local
materials possible and usually result in the most economical
design.
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4. Conventional Flexible Pavement
Cross section consist
 Cross section consist of (from top):
1. Seal coat
2. Surface course
3. Tack coat
4. Binder course
5. Prime course
6. Base course
7. Sub base course
8. Compacted sub grade
9. Natural sub grade
 The use of various courses is based on either necessity or
economy, and some of the courses may be omitted.
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5. Conventional Flexible Pavement - Typical Cross Section
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6. Seal Coat
 Seal coat: Thin asphalt surface treatment used to:
1- Waterproof or seal the surface.
2- Rejuvenate or revitalize old bituminous wearing surfaces.
3- To nonskid slippery surfaces.
4- Improve night visibility.
 Single Surface treatment = single application of bituminous material
that is covered by a light spreading of fine aggregate or sand (spread
mechanically) then compacted with pneumatic tired rollers.
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7. Seal Coat
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8. Surface Course
Surface Course: Is the top course of asphalt pavement (Wearing
course).
 Constructed of dense graded HMA.
 Must be:
1- Tuff to resist and withstand wear & abrasive effects of moving
traffic & stable to prevent permanent deformation.
2- Provide smooth and skid resistant riding surface.
3- Water proof to protect the entire pavement from the weakening
effects of water.
 If the above requirements can not be met, the use of seal coat is
recommended.
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9. Dr.Majed Msallam 44
Surface Course

10. Binder Course
 Binder course (known also as Asphalt base course) is the
asphalt layer beneath the surface course.
 Reasons for use:
1- HMA is too thick to be compacted in one layer (if the binder
course is more than 3” it is placed in two layers).
2- More economical design, since binder course generally
consist of larger aggregates and less asphalt and doesn’t
require high quality.
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11. Tack & Prime Coats
 Tack coat (RC): Very light application of asphalt
(emulsion) to ensure a bond between the surface
being paved and the overlying course.
 Binds asphalt layer to PCC base or to an old asphalt
pavement.
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12. Tack & Prime Coats
 Prime coat: Application of low viscosity Cutback
asphalt to an
absorbent surface such as untreated granular base
on which asphalt layer will be placed on.
• It binds the granular base to the asphalt layer.
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13. Tack & Prime Coats
 Tack coat doesn’t require the penetration of asphalt into the
underlying layer, while
 prime coats penetrates
into the underlying layer,
plugs the voids , and form
a watertight surface.
 Both are spray application.
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14. Base & Sub Base Courses
 Base course: Layer immediately beneath the surface or binder
course.
 Composed of crushed stone, crushed slag, or other untreated or
stabilized materials.
 Has good stability & density
 Distributes & spreads the stresses created by wheel loads so that the
stresses transmitted to the sub grade will not be great to result in
excessive deformation or displacement of that foundation.
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15. Sub base Course
 Sub base course: Layer beneath the base course, used
mostly for economy purposes since it can be of lower quality.
 Sub bases may be used in areas where:
1- frost action is sever, or
2- Sub grade soil is extremely weak, or
3- Where construction working table is needed.
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16. Sub Base Courses
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17. Sub grade
 Sub grade can be either in situ soil or a layer of selected
materials.
 The top 6” of sub grade should be scarified and compacted to
the desired density near the optimum moisture content.
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18. Sub grade
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