Concept explainers
The structural components of a flexible pavement.
Explanation of Solution
The structural components of a flexible pavement are as follows:
- The subgrade or prepared roadbed,
- The subbase,
- The base and
- The surface course.
It is necessary to check for the evaluation of every component of the flexible pavement and
Subgrade (Prepared Roadbed)
It is first in the line of materials that are to be laid and serves as the foundation of the flexible pavement structure. It is being spread along the horizontal alignment of the pavement. The materials used in this layer are very well compacted to meet the prescribed specifications of strength. In this layer, borrow materials may also be used according to the pavement being constructed.
Subbase Course
This layer is kept above the subgrade and the materials used in this layer are of better quality as compared to that of the materials used in subgrade. The materials used in this flexible pavement structure must meet the specifications in terms of gradation, strength and plastic characteristics.
And in case, if the materials for the subbase course aren't readily available then the subgrade materials are treated to meet the specifications that of the subbase course material properties.
Base Course
This course comes at the third place in the line of pavement structures. It isplaced just above the subbase course and if subbase is not used then it lies immediately above the subgrade of the pavement structure. The materials that are used in this pavement section are of much better quality then those used in the previous layers in terms of gradation, strength and plastic requirements. Granular materials likestone,slag, gravel, and sand are used in this course of flexible pavement structure.Wherein, slag and gravel can be used in both forms i.e., (crushed or uncrushed) stones should be crushed. In case if some of the materials are not meeting the specifications for this line of course then they are used in the base if appropriately stabilized with Portland cement, lime or asphalt.For high quality pavements the material is treated with Portland cement or asphalt to improve the stiffness characteristics of such pavements.
Surface Course
This is the topmost layer of the flexible pavement and is placed above the base course of the road pavement. The materials in this pavement include a mixture of aggregates and asphalt. The properties of this material must be able to hold out against the high tire pressure, withstand abrasive forces due to the traffic flow, prevention against the infiltration of surface water to avoid rupturing of surface course and weakening of the underlying structural bed of the pavement. Considering the expected traffic flow the thickness of this layer varies from 3 inches to 6 inches.
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Chapter 19 Solutions
MindTap Engineering for Garber/Hoel's Traffic and Highway Engineering, 5th Edition, [Instant Access], 1 term (6 months)
- Compare flexible and rigid pavement construction for a new highway.arrow_forwardWrite the significance of each layer of flexible pavement in a single line. B) Describe the one most important factor of causing failure of highway subgradearrow_forwardProblem 1: Make a diagram showing the comparison between Flexible and Rigid Pavement. Categorize the comparison based on the type and number of layers, materials used, design input data, suitability, durability etc. Note: For reference use AASHTOarrow_forward
- 2- Describe six of the main differences between rigid and flexible pavements.arrow_forwardBriefly explain the process of constructing a pavement using roller-compacted concrete (RCC). What are the advantages and disadvantages of this method of construction?arrow_forward2. What are various failures in Flexible Pavement’s, explain with the help of diagrams?arrow_forward
- Failure of Flexible Pavements, their causes and repairarrow_forward. Say what is the main purpose of the pavement or pavement layers, and then draw the flexible pavement layers respectively.arrow_forwardMechanistic design procedure is based on the assumption that a pavement can be modelled as multi-layered elastic or viscoelastic. Discuss the combination of Visco-elastic considerations assumption in pavement design procedure.arrow_forward
- Traffic and Highway EngineeringCivil EngineeringISBN:9781305156241Author:Garber, Nicholas J.Publisher:Cengage Learning