Flexible Pavement Design And Comparision Essay


Discuss about the Flexible Pavement Design And Comparision.


Executive Summary

Pavement designs are able to happen in many forms considering the pavement uses. Comparing the different is essential to ensure that the different design parameters are met according to pavement use. This project will be able to offer comparison factors of the flexible pavement design with other alternative pavements (Jackson, Puccinelli & Mahoney, 2014). This will be done through the use of Indian Roads Congress 37-2012, which is able to specify the design procedures for the flexible roads based on the CBR values. The main finding should be able to indicate different CBR values. The use of the roads determines the requirement of the different design parameters where CBR is the main design parameter for the flexible pavements.


Pavements are classified in different categories according to the materials used. Major two pavement classifications are Asphalt (flexible) pavement and concrete (rigid) pavement. The flexible pavements have different layers, which vary in width during the design period. Additionally, other pavement designs also has different layers but not as in the flexible pavements. There are clear differences, which are attained and experienced when the design of these pavements is happening. The major layers include subgrade, sub-base, base and binder and/or surface (Kazda & Caves, 2015). Determining the different CBR values of the different layers is able to offer the main difference in the design of the pavements. The flexible pavements do deflect upon loading and therefore the name. Each layer of the pavements is able to carry certain load, which they pass to the other below. Moreover, the rigid pavement has little deflect upon loading due to the high modulus of elasticity (Liu, 2016). Weight distribution and CBR values are key design factors, which offer major differences on the pavements. This proposal will be able to define the procedure of analyzing different pavements options ion terms of their design and compare with the flexible pavements design. The IRC 37-2012 will offer the basis of the CBR for the subgrade and the effectiveness of this key experiment. Additionally, the design of the pavement will be based on th IIT PAVE.

State-of-the-art/Literature Review

The designs of pavements have been critical to different economies. Different design parameters have to be treated differently to enhance their main aim. The use of the pavements set up the design procedure for the pavements (National research council (U.S.), et al., 2016). The combinations of the traffic factors and materials properties have been critical in defining the differences of the pavement designs. Treatments of the pavement materials, together with the layer widths are critical parameters, which are attained in the designs. In India, there are different classifications of pavements, which are done by the categories of the pavements and the authorities who manage them (National research council (U.S.), 2014b). Some of the key classification includes national Highways (NH), State Highways (SH), Major District Roads (MDR), Other District Roads (ODR) and Village Roads (VR). The pavements have different widths of the layers. Some of these classifications are able to consist of the flexible pavements while others may exist as rigid or semi rigid pavements.

Moreover, there are different combinations of designs of traffic and material properties in the design of the pavements in order to meet the specific requirements of the pavements. Each combination is able to lead to different design thickness of the layers (Kazmee & Tutumluer, 2015). Some of the combinations, which are able to lead to differences in different types of pavements include;

  1. Both Granular Base and Granular sub-base
  2. Combination of Cementitious Base and Cementitious Sub-base of aggregate interlayer for crack relief.
  3. Cementitious base and sub-base which has SAMI at the interface of base and the bituminous layer.
  4. Foamed bitumen/bitumen emulsion treated RAP
  5. Cementitious base and granular sub-base with crack relief layer of aggregate layer above the cementitious base.

During the design of the pavements, the design allows the transfer of the stresses with the top layer carrying the most stress and subgrade the least. The amount of the stress is able to depend on the design of the pavements, whether flexible or rigid (National research council (U.S.), 2015). The determinant factors are the wheel loads which dictate the thickness of the layer. In the design procedure for the flexible pavements, the process is aimed at providing the appropriate layer thickness and composition (Chinese-European pavement design, 2016). The main design factors, which are able to indicate the diff erences in pavement design, are the stresses due to the traffic load and temperature variations. The key layer, which is much focused on any pavement design, is the subgrade layer. The strength of the pavement is able to depend on this layer and the CBR is usually carried on the layer. The CBR factors are able to offer the key difference on the design of the pavement (National research council (U.S.), et al., 2014). The layer is done with relation to the design life which the pavement is expected to last. Generally, the rigid pavements are meant to last for more than thirty years while the flexible pavements are designed to last for between ten and twenty years (National research council (U.S.), 2014a). This design life is able to offer the design factors and thickness of the layer considering the different traffic loadings on the sections.

In addition, the materials states are key in the design of the pavements. Since the different pavements are able to have different materials, their state are able to determine the design procedure and therefore able to bring out a difference. Some of the key pavement designs, requires special treatment of the materials used in order to meet the specific needs of the pavement type (Hu, Zhou & Scullion, 2014). In addition, the design parameters are able to dictate the arrangement of the different materials. For instance, granular base and subbase are used for some key flexible pavements (Hamdi, 2015). Using different materials on these layers are able to bring out another key design parameter. In addition, the change of materials on the subgrade layer is able to lead to change in the CBR values for the pavements.

Research Question, Aim/Objectives and Sub-goals

The main research question, which will be addressed on this proposal, is the key differences which are able to exist in the design of the pavements. More specifically, the research proposal will address what are the key differences in the CBR values for the different layers of flexible pavement design against other pavement designs? In addition, the proposal will look at the differences in design strength, which the different pavements are able to bear for them to last for the specified design life.


The objectives of this proposal will be able to compare different design processes for the pavement design. This will helps to make conclusion on which design process is better to achieve the best results. In order to attain this objective, the researcher will perform several experiments on different pavement designs to identify the differences clearly. The experiments will help to identify the CBR values and the required thickness of the specific layers of both the pavements under consideration.


Several methodologies will be applied on the research proposal in order to achieve the set objectives. Data and material collection will be done in advance. Then the process of design and laboratory test will proceed. Lastly, the project will involve on comparative analysis of the different results of the pavement designs. An analysis of the RAP bitumen emulsion mix will be carried out through compaction to achieve maximum density which will only be at optimum fluid content. Moreover, the compaction tests will be carried out at different fluid content in order to arrive at the optimum fluid content. The major basis for this process will be on Manual 14 ‘The design and Use of Granular Emulsion Mixes’ which will be defining the mix design. In addition, the users will be able to adopt other methods of mix design given in ‘Cold Mix Recycling’ and ‘Asphalt cold Mix Manual (MS-14)’. The bitumen will be used in order to achieve the required minimum strength. Water will be critical in the process and 1.5 to 2.5 per cent water will be added to the RAP mixes. This will be to cater for the rapid evaporation of water from the RAP mixes considering the hot weather. This will be to aid the attaining of maximum compaction and strength gain. Additionally after laying of RAP mix, the top layer of the pavement will be able to stand the construction traffic due to loss of water on hot sunny days. Soil testing will be done to determine the different layers which can be designed.

Experimental Setting

Experimental set up will be done on the laboratory to achieve the results needed. One of the key experiment, which will be carried out on this project, will be the CBR test. The CBR experimental process will be key in the determination of the layer thickness. In addition, the CBR experiment setting will help to evaluate the strength of a subgrade soil, sub base and base course material. This process will be key in the design of thickness for highways and airfield pavement. Another key experimental set up which will be done will be the moisture content measurement in the laboratory. Optimum moisture content is defined as the water content at which the soil attains the highest density when compacted by a specific amount of energy. Therefore, it is very important to know the OMC, and in this project, the main aim will be to arrive at a standard level, which may serve as a guide and a basis of comparison for field compaction. Through the project, the standard proctor test of compaction was carried out on the soil in the lab. IIT PAVE software will be used in the design process for the different pavements. The comparison will be then made based on the different results which will be achieved from the software.

Project risks

Coordination of the information with the different parties will be a key risk which the project will experience. Some parties may be unwilling for offer assistance in terms of the information needed.

Results, Outcome and Relevance

The data from the CBR and the moisture content will be key in the design of the pavements. The data will help to form the bases of the argument and determine the differences in the design of the different pavements. The thickness of the different layers will be investigates in accordance to the design process. This will help to conclude on the outcome that the design process is key in the different pavement types.

Project Planning and Gantt Chart

Activity/ month








Proposal writing

Defending the proposal

Data collection

Collection of materials

Preparation of materials for testing

Performing the tests

Writing final report and presentation


Flexible pavement design is able to differ with other forms of pavement design from different perspectives. The layers composition and their thickness are some of the key parameters which are different on these pavement designs. The CBR values are able to dictate the design parameters for the pavements and will be used on the project to determine the differences on this kind of designs. The Indian Roads Congress 37-2012, which is able to specify the design procedures for the flexible roads, based on the CBR values. During the design of the pavements, the design allows the transfer of the stresses with the top layer carrying the most stress and subgrade the least. The amount of the stress is able to depend on the design of the pavements, whether flexible or rigid.



HAMDI, A. (2015). Local calibration of AASHTOWare® using Ontario pavement management system data PMS2. Thesis (Ph.D)--University of Waterloo, 2015.

HU, S., ZHOU, F., & SCULLION, T. (2014). Development of Texas mechanistic-empirical flexible pavement design system (TxME).

JACKSON, N. C., PUCCINELLI, J., & MAHONEY, J. P. (2014). Using existing pavement in place and achieving long life.

KAZDA, A., & CAVES, R. E. (2015). Airport design and operation.

KAZMEE, H., & TUTUMLUER, E. (2015). Evaluation of aggregate subgrade materials used as pavement subgrade/granular subbase.

LIU, X. (2016). Functional Pavement Design IV. CRC Press.


NATIONAL RESEARCH COUNCIL (U.S.). (2014a). Pavement management, 2014.

NATIONAL RESEARCH COUNCIL (U.S.). (2014b). Pavement management, 2014. Volume 3. Volume 3.

NATIONAL RESEARCH COUNCIL (U.S.). (2015). Pavement management. Volume 2. Volume 2.

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