PAVEMENT DESIGN FUNDAMENTALS
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The document discusses different types of pavements. It describes flexible pavements as having multiple layers that distribute loads through aggregate interlock. Rigid pavements distribute loads through the beam strength of concrete slabs. Flexible pavements are composed of surface, base, and sub-base layers over a subgrade, while rigid pavements typically only require a concrete surface layer. Both pavement types are designed to reduce loads from vehicles to prevent damage to the subgrade. The document compares advantages and disadvantages of flexible and rigid pavements.
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PAVEMENT DESIGN FUNDAMENTALS
- 1. TOPIC:- PAVEMENT DESIGN SUBMITED TO: ASSISTANT PROF. GAJENDRA RAGHUWANSHI SUBMITED BY: RANJAN KUMAR
- 2. What is a Pavement? A multi layer system that distributes the vehicular loads over a larger area 2
- 3. What is a Pavement? OR Highway pavement is a structure consisting of superimposed layers of selected and processed materials whose primary function is to distribute the applied vehicle load to the sub grade. OR It can also be defined as “structure which separates the tires of vehicles from the under lying foundation.” 3
- 4. What is a Pavement? Pavement is the upper part of roadway, airport or parking area structure It includes all layers resting on the original ground – It consists of all structural elements or layers, including shoulders 4
- 5. Functions of the Pavement Reduce and distribute the traffic loading so as not to damage the subgrade – Provide vehicle access between two points under all-weather conditions – Provide safe, smooth and comfortable ride to road users without undue delays and excessive wear & tear – Meet environmental and aesthetics requirement – Limited noise and air pollution – Reasonable economy 5
- 6. Requirements of pavement structure Sufficient thickness to spread loading to a pressure intensity tolerable by subgade Sufficiently strong to carry imposed stress due to traffic load Sufficient thickness to prevent the effect of frost susceptible subgade Pavement material should be impervious to penetration of surface water which could weaken subgade and subsequently pavement Pavement mat. shd be non-frost susceptible Pavement surface shd. be skid resistant 6
- 8. Types of Pavement 8 Flexible Pavements PAVEMENTS Rigid Pavements
- 9. 9 Natural Soil (Subgrade) Aggregate Subbase Course Aggregate Base CourseAsphalt Concrete Flexible Pavements
- 10. 10 Given Wheel Load Load Distribution in Flexible Pavements Flexible Pavements 150 psi 3 psi Wearing C. Base Sub-base Sub-grade
- 12. 12 Rigid Pavements Load Distribution in Rigid Pavements
- 13. 13 Pavements Comparison Flexible pavements: • Deep foundations / multi layer construction • Energy consumption due to transportation of materials • Increasing cost of asphalt due to high oil prices Rigid pavements • Single layer • Generally last longer • May require asphalt topping due to noise / comfort issues
- 14. 14 Pavements Comparison • Heavy vehicles consume less fuel on rigid pavements • Rigid pavements more economic when considering environmental / life-cycle costing
- 15. Flexible Pavement “A flexible pavement is a structure that maintains intimate contact with and distributes load to the sub grade and depends on aggregate interlock, particle friction and cohesion for stability” 15
- 16. OR It is a structure which distributes the traffic loading stresses to the soil (sub grade) at a magnitude that will not shear or distort the soil i.e., from 150 psi to 3 psi OR Pavement which reflects deformation of sub grade & the subsequent layers on to the surface” i.e.; load is transmitted from grain to grain through contact points of granular material, i.e. in a compressive way. 16 FlexiblePavement
- 17. Flexible Pavement Flexible pavements Elastic Three main layers Surfacing Wearing course Base course Road base Sub base Supported by Sub-grade 17
- 18. 18 Load Distribution In Flexible Pavements
- 19. Structure of Flexible Pavement In order to take maximum advantage of this property, material layers are usually arranged in order of descending load bearing capacity with the highest load bearing capacity material (and most expensive) on the top and the lowest load bearing capacity material (and least expensive) at the bottom. 19
- 20. 20 – Surface Course: This is the top layer and the layer that comes in contact with traffic. – Base Course: This is the layer directly below the surface course and generally consists of aggregates (either stabilized or un-stabilized). – Sub-base Course: This is the layer (or layers) under the base layer. A sub- base is not always needed. Structure of Flexible Pavement
- 21. 21 – Sub-grade Course: The "sub-grade" is the material upon which the pavement structure is placed. Although there is a tendency to look at pavement performance in terms of pavement structure and mix design alone. The sub- grade can often be the overriding factor in pavement performance. Structure of Flexible Pavement
- 22. Surface Course The surface course is the layer in contact with traffic loads and normally contains the highest quality materials. It provides characteristics such as friction, smoothness, noise control, rut and shoving resistance and drainage. 22
- 23. Base Course The base course is immediately beneath the surface course. It provides additional load distribution and contributes to drainage and frost resistance. Base courses are usually constructed out of: Aggregates: Base courses are most typically constructed from durable aggregates that will not be damaged by moisture or frost action. Aggregates can be either stabilized or un-stabilized. 23
- 24. 24Lime rock Base Course Undergoing Final Grading
- 25. Sub-base Course The sub-base course is between the base course and the sub-grade. It functions primarily as structural support but it can also: Minimize the intrusion of fines from the sub-grade into the pavement structure. Improves drainage. Minimize frost action damage. Provides a working platform for construction. 25
- 26. Sub-base Course The sub-base generally consists of lower quality materials than the base course but better than the sub- grade soils. A sub-base course is not always needed or used. For example, a pavement constructed over a high quality, stiff sub-grade may not need the additional features offered by a sub-base course so it may be omitted from design. 26
- 27. Sub-grade • Sub-grades be composed of a wide range of materials although some are much better than others. This subsection discusses a few of the aspects of sub-grade materials that make them either desirable or undesirable and the typical tests used to characterize sub-grades. 27
- 28. 28 Sub-grade Preparation Sub-grade Failure Crack
- 29. Types of Flexible Pavement 29 Dense-graded Open-graded Gap-graded
- 30. Flexible Pavement – Construction 30
- 35. 35 Wheel Load Sub-grade Bituminous Layer Typical Load Distribution in Flexible Pavement
- 36. Rigid Pavement Rigid pavements are those, which contain sufficient beam strength to be able to bridge over the localized sub-grade failures and areas of in adequate support. OR Load is transmitted through beam action of slab in rigid pavements. OR Rigid pavements are those, which reduces the stress concentration and distributes the reduced stresses uniformly to the area under the slab. 36
- 37. Rigid Pavement Rigidity – does not deform under stress Concrete – air entrained increases resistance to frost damage and de-icing salt corrosion Reinforcement – may be bars or mesh. Continuous rigid pavements have heavy reinforcement Joints – used in non-continuous pavements to allow for thermal movement. Includes a ‘filler’ and surface sealant Rigid pavements – laid as single layer by ‘concrete paver’ 37
- 39. Basic Components of Concrete Pavement 39
- 41. 41 Rigid Pavements Load Distribution in Rigid Pavements
- 42. Rigid Pavements Because of its relative rigidity, the pavement structure distributes loads over a wide area with only one, or at most two, structural layers. There are other types of surfaces also i.e.; reinforced, continuously reinforced etc. 42
- 43. Structure of Rigid Pavement Surface course. This is the top layer, which consists of the PCC slab, reinforced or continuously reinforced slabs . Base course. This is the layer directly below the PCC layer and generally consists of aggregate or stabilized sub-grade. Sub-base course. This is the layer (or layers) under the base layer. A sub-base is not always needed and therefore may often be omitted. 43
- 44. 44 Surface Course • The surface course is the layer in contact with traffic loads and is made of PCC or RCC. It provides characteristics such as friction, smoothness, noise control and drainage. In addition, it serves as a waterproofing layer to the underlying base, sub-base and sub-grade. • The surface course can vary in thickness but is usually between 150 mm (6 inches for light loading) and 300 mm (12 inches for heavy loads and high traffic). Figure shows a 300 mm (12 inch) surface course.
- 45. 45 PCC Surface Rigid Pavement Slab (Surface Course) Thickness
- 46. 46 Base Course • The base course is immediately beneath the surface course. It provides • Additional load distribution, • Contributes to drainage and frost resistance, • Uniform support to the pavement and • A stable platform for construction equipment. Bases also help and prevent sub grade soil movement due to slab pumping. Base courses are usually constructed out of: – Aggregates base. A simple base course of crushed aggregates has been a common option since the early 1900s and is still appropriate in many situations.
- 47. 47 – Stabilized aggregate or soil. Stabilizing agents are used to bind otherwise loose particles to one another, providing strength and cohesion. Cement treated bases (CTB s) can be built to as much as 20 - 25 percent of the surface course strength. – Dense-graded HMA. In situations where high base stiffness is desired base courses can be constructed using a dense-graded HMA layer. – Permeable HMA. In certain situations where high base stiffness and excellent drainage is desired, base courses can be constructed using an open graded HMA. Base Course
- 48. 48 Completed CTB with Curing Seal Lean Concrete Base Material
- 49. 49 Sub-base Course • The sub-base course is the portion of the pavement structure between the base course and the sub-grade. It functions primarily as structural support but it can also: – Minimize the intrusion of fines from the sub-grade into the pavement structure. – Improves drainage. – Minimizes frost action damage. – Provides a working platform for construction. • The sub-base generally consists of lower quality materials than the base course but better than the sub- grade soils. Appropriate materials are aggregates and high quality structural fill.
- 50. Types of Rigid Pavement Jointed Plain Concrete Pavement (JPCP) 50
- 51. Types of Rigid Pavement Continuously Reinforced Concrete Pavement (CRCP) 51 Photo from the Concrete Reinforcing Steel Institute
- 53. 53 Pavements Comparison Flexible pavements: • Deep foundations / multi layer construction • Energy consumption due to transportation of materials • Increasing cost of asphalt due to high oil prices Rigid pavements • Single layer • Generally last longer • May require asphalt topping due to noise / comfort issues
- 55. Types of Pavement Failure Failure criteria Flexible Pavements Fatigue Cracking, Rutting, Thermal Cracking, Rigid Pavements Fatigue Cracking, Pumping or Erosion Others: Faulting, spalling, joint deterioration 55
- 56. Flexible vrs. Rigid Pavements 56
- 57. Flexible vrs. Rigid Pavements 57
- 59. 59 THANKS
Editor's Notes
- Heavy vehicles cause greater deflection on flexible pavements rather than on rigid pavements. When the pavement deflects or moves, it absorbs a portion of the vehicle energy that otherwise would be available to propel the vehicle forward. Concrete’s rigid design reduces the pavement’s deflection and corresponding fuel consumption. Also smoothness of concrete pavements is less affected by seasonal changes, which could also contribute to lower fuel consumption.
- Heavy vehicles cause greater deflection on flexible pavements rather than on rigid pavements. When the pavement deflects or moves, it absorbs a portion of the vehicle energy that otherwise would be available to propel the vehicle forward. Concrete’s rigid design reduces the pavement’s deflection and corresponding fuel consumption. Also smoothness of concrete pavements is less affected by seasonal changes, which could also contribute to lower fuel consumption.
- More in pavement guide interactive Stevens Way will be fixed form starting in May
- Heavy vehicles cause greater deflection on flexible pavements rather than on rigid pavements. When the pavement deflects or moves, it absorbs a portion of the vehicle energy that otherwise would be available to propel the vehicle forward. Concrete’s rigid design reduces the pavement’s deflection and corresponding fuel consumption. Also smoothness of concrete pavements is less affected by seasonal changes, which could also contribute to lower fuel consumption.