Flixible Pavement Layers
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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.
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Flixible Pavement Layers
- 1. Pavement Types- Flexible pavement Cross section Dr.Majed Msallam 33 Subgrade Base Coarse BBC BWC
- 2. Flexible Pavement Types 1- Conventional Flexible Pavement. 悋惘惶悸 悋惠惆悸 悋悒愕惠悸 悋惺 悵悋 悋惘惶悸 惆愕 悴惺悸 愀惘惠 悋悖惘悸 悋悋惶悋惠 悋愀惘 AASHTO 惠惠 忰惓 悋惘惶悸 惘悧愕悸 愀惡悋惠 惓悋惓 惺 悋惆惘悸 忰惓 悋惆 惺悸 悖惷 惠 悖 悋愕愀忰 愀惡悸 惠愕 悋惺悋 悋愀惡悸 悋惠忰 悋悒愕惠悸 悋愀惡悸 SURFACE COURSE 悋悖愕悋愕 愀惡悸 惠悋 BASE COURSE 惓 悋悖愕悋愕 惠忰惠 悋 愀惡悸 SUBBASE COURSE 悵 悽悋 悋惘惘悸 悋忰悋惠 惠悖惓惘 惠 惆惘惠悋 惠 悖 惠惘惷 悋惠 悋惠惘惡悸 悒 悋愀惡悋惠 悴惘 悋 愃悋惡悋 愕惡悋 惺悋悸 悋惠忰 惺 惆悋 COMPACTED SUBGRADE 悋惶悋惠悋 惠忰愕 . Dr.Majed Msallam 37
- 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. Dr.Majed Msallam 38
- 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. Dr.Majed Msallam 39
- 5. Conventional Flexible Pavement - Typical Cross Section Dr.Majed Msallam 40
- 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. Dr.Majed Msallam 41
- 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. Dr.Majed Msallam 43
- 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 doesnt require high quality. Dr.Majed Msallam 45
- 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. Dr.Majed Msallam 46
- 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. Dr.Majed Msallam 47
- 13. Tack & Prime Coats Tack coat doesnt 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. Dr.Majed Msallam 48
- 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. Dr.Majed Msallam 49
- 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. Dr.Majed Msallam 50
- 16. Sub Base Courses Dr.Majed Msallam 51
- 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. Dr.Majed Msallam 52
- 18. Sub grade Dr.Majed Msallam 53