Technical-economic feasibility of using sustainable pavements in Iran

Master's Thesis

Civilization - Road and Transportation

) General

Pavements are usually affected by various factors that affect their life. Since a road passes through different areas where the subsoil, the type and volume of traffic and the climatic conditions of these areas are different from each other, therefore, various disadvantages and defects arise in different lengths of a road, which, if they are not addressed, evaluated and repaired, will cause the rapid deterioration of the road and the destruction of huge national capitals and the dissatisfaction of the users, therefore, a pavement of good quality and with a suitable life has been considered and those things that lead to increasing the durability, quality and life of asphalt pavements has always been the focus of road construction industry experts and practitioners, and they aim to increase the service life of pavements by conducting research and laboratory and field studies every day.

With the increase in traffic and the cost of maintaining pavements, researchers have planned and implemented pavements that can have a longer lifespan than the existing pavements and during this period, have the ability to properly serve more traffic without the need for structural maintenance. These cases led to the introduction of pavements under the title of durable pavements and long-life pavements.

Recent efforts in material selection, mix design, performance tests, and pavement design suggest a method that obtains long-life performance from asphalt pavement structures (more than 50 years) until the pavement surface is replaced periodically.

A durable pavement uses multiple layers of durable asphalt. slow to get a safe, smooth and long-lasting road. The design begins with a strong yet flexible base layer that resists the tensile strain caused by traffic as well as pavement rutting in the wheel path. Asphalt must be thick enough to resist bending and prevent cracks at the bottom of the asphalt layer.

The middle layer completes the permanent structural part and is a final layer for the rutting position and is a surface that does not need to be repaired for a long time. This layer can be designed for rutting resistance using high quality aggregates and polymer bitumens.

The top layer is a replaceable surface that can be designed for specific functions. In some cases, it is appropriate to use a mixture with dense granulation according to the regulations. In areas with very high traffic, the use of SMA1 can be desirable, provided that the materials for its construction are available, and in some cases, engineers want to use an open-grained asphalt layer (2OGFC) on the surface to prevent noise and water and provide better slip resistance during rain. Both OGFC and SMA have a very good performance in reducing road noise.

1-2) Definition of the problem and importance of the issue

Since the initial design and construction plays a significant role in the repair and maintenance of the pavement during its service life and the performance quality of the pavement is independent of weather conditions, incoming load, quality of materials and its mixing design, therefore, by choosing the right materials and taking into account other effective factors, the service life of the pavement can be increased and as a result, the future costs of its repair can be reduced.

1.Stone Matrix Asphalt

2.Open Graded Friction Course

Unfortunately, in our country due to the abundance of oil resources and the excessively cheap price of bitumen compared to countries without these resources, no importance is given to bitumen, improving the performance of bitumen, mixing plan, quality control of materials used in the road surface and appropriate methods for design. So that the country's road network and even airports are an objective collection of all types of pavement failures, and the costs of these failures are directly or indirectly imposed on road users. While it is possible to improve the durability and performance of the pavement to an acceptable level with proper design and life management. Due to the many failures and the short life of pavements, other countries of the world, especially the United States, sought to build pavements that have a long life and reduce failures as much as possible. This research led to the invention of a new type of long-life pavements called sustainable pavements. In addition to a life of over 50 years, this type of pavement has benefits such as low repair and maintenance during the useful life period, lower life cycle cost than others.In addition to a life of over 50 years, this type of pavement has benefits such as low repair and maintenance during the useful life period, lower life cycle cost than other pavements, and so on.

Although the damage of roads in Iran is very high and the cost and time of construction and repair are high, no research has been done on this type of pavement in Iran. Therefore, in this thesis, while examining the performance of these pavements in the world, by using finite element modeling, this type of pavements has been investigated in order to create more knowledge for design by examining the parameters affecting its performance.

1-3) The purpose of the research

The quality and thickness of asphalt mixtures is one of the influencing factors in the performance of pavements and especially the creation of lizard skin cracks. The use of low-quality or low-thickness mixture leads to spending exorbitant costs for the repair and maintenance of pavements. Therefore, the purpose of this research is to evaluate the materials and predict the performance of the mixture in the design stage.

In the past, hot asphalt materials were considered as solid elastic in the mechanistic analysis for flexible asphalt pavements, while in fact they behaved like viscoelastic materials. Unlike elastic solids, the behavior of asphaltic materials basically depends on the temperature and frequency of loading. At low temperature and high loading frequency, they behave more like an elastic solid, while at high temperature and low loading, they behave like a viscous liquid. In medium temperature and loading frequency, they behave like visco-elastic materials, which have a level of hardness of solid elastic materials, in addition to showing the main properties of visco materials.

The main goal of the research is to introduce the properties of visco-elastic materials that have been measured in the laboratory to simulate the pavement behavior in the 3D finite element model. This model was made for the permanent pavement of U.S. 30 in Ohio in the United States. 1-4) Research method According to the objectives described above and in order to achieve these objectives, the research method and study program will be as follows: - Examining the subject and collecting information - Selection of materials - Conducting the required tests - Calculation of software input parameters

- Modeling of permanent pavement using ABAQUS software

- Examining the results and the effect of different pavement factors on the obtained model

- Economic comparison

- Conclusion and offering suggestions

1-5) Hypothesis

The available hypotheses for this thesis are as follows:

A- Materials used in the modeling of finite elements in accordance with the standards intended for pavement construction

B- The laboratory results to determine the characteristics of the materials as well as the results of the field tests have sufficient accuracy.

C- The finite element software ABAQUS has sufficient ability to simulate this pavement and can correctly estimate the required response values ??of the pavement.

1-6) Dissertation division and definition of chapters

This thesis consists of six chapters as follows:

In the first chapter, which is the introduction, it introduces the thesis and includes general parts, the importance of the topic, research objectives, research methods, and finally, the division of the thesis and the definition of chapters. In the second chapter, which is the introduction of sustainable pavement, a general definition of sustainable pavement, its benefits, suitable methods for design, characteristics of different asphalt layers required for this type of pavement, review of subgrade characteristics and introduction of several sustainable pavements built in the world are presented. In the third chapter, the background of the research has been reviewed and the methods used for research on sustainable pavement have been introduced and a summary of the research conducted by various researchers has been given. In the fourth chapter, the materials selected for modeling are mentioned and the experiments used in this research are introduced and the parameters needed to be defined as input in the software are calculated. In the fifth chapter, which is modeling with ABAQUS software, a definition of this software is provided first, and then the built model is explained in detail. The output of the model is given and parametric studies are carried out on these results. Finally, a comparative comparison is made between this pavement and ordinary asphalt pavement. In the sixth chapter, there are results, suggestions and references.

2-1) Introduction

The theory of sustainable pavements or long-life pavements is not a new topic.