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Comparison Of Cost On The Design Of Flexible And Rigid Pavement

The research work had been focused on the specific objectives to determine and compare the life cycle costs of rigid and flexible pavements and to investigate all other qualitative merits of rigid and flexible pavement.

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ABSTRACT

Road construction projects have been implemented all over Nigeria as part of the national development plan. Roads are one of the country’s basic infrastructural facilities where high amounts of budget allocated every fiscal year planning period. Since the cost comprises of a large portion of government investment, a careful evaluation of the alternatives is utmost importance to make the right choice for a particular project. In the history of Nigeria road development program, almost all of the road pavements are flexible, and it demands high foreign currency for asphalt material importing from abroad. In addition, flexible pavement needs to be maintained and rehabilitated within a few years after its initial construction. In view of the emerging cement factories and the availability of cement in Nigeria, it is practical to consider rigid pavement as one of the alternatives. Relative to this, the research project was conducted with the main objective of identifying the cost of rigid and flexible pavements at Nigeria roads. The research work had been focused on the specific objectives to determine and compare the life cycle costs of rigid and flexible pavements and to investigate all other qualitative merits of rigid and flexible pavement.

CHAPTER ONE

1.0                                                                              INTRODUCTION

Transportation has been one of the essential components of the civil engineering profession since its early days. From time immemorial, the building of roads, bridges, pipelines, tunnels, canals, railroads, ports, and harbors has shaped the profession and defined much of its public image. As cities grew, civil engineers became involved in developing, building, and operating transit facilities, including street railways and elevated and underground systems [1]. The role of civil engineers is to providing transportation infrastructure to accommodate a growing population. The transportation by road is the only road which could give maximum service to one all. This mode has also the maximum flexibility for travel with reference to route, direction, time and sped of travel. It is possible to provide door to door service only by road transport [2].

Pavement is the actual travel surface especially made durable and serviceable to withstand the traffic load commuting upon it. Pavement grants friction for the vehicles thus providing comfort to the driver and transfers the traffic load from the upper surface to the natural soil. In earlier times before the vehicular traffic became most regular, cobblestone paths were much familiar for animal carts and on foot traffic load. Pavements are primarily to be used by vehicles and pedestrians. Storm water drainage and environmental conditions are a major concern in the designing of a pavement. The first of the constructed roads date back to 4000 BC and consisted of stone paved streets or timber roads. A highway pavement is a structure consisting of superimposed layers of processed materials above the natural soil sub-grade, whose primary function is to distribute the applied vehicle loads to the sub-grade [3]. The pavement structure should be able to provide a surface of acceptable riding quality, adequate skid resistance, favorable light reflecting characteristics, and low noise pollution. The ultimate aim is to ensure that the transmitted stresses due to wheel load are sufficiently reduced, so that they will not exceed bearing capacity of the sub grade. The roads of the earlier times depended solely on stone, gravel and sand for construction and water was used as a binding agent to level and give a finished look to the surface. All hard road pavements usually fall into two broad categories namely

  1. Flexible Pavement
  2. Rigid Pavement

In this work, the cost of constructing and using the two types of pavement are compared in terms of suitability and durability.

1.1                                                              BACKGROUND OF THE STUDY

In many countries with developed road networks, new road construction typically accounts of more or less 50% of the road budget. While the remainder of national road budgets is spent on maintenance and rehabilitation of existing roads. Long-life Pavements (LLP) project is approved if the costs of future maintenance, rehabilitation and the resulting road user delay costs are economically justified [8].

There has been historically difference of opinion as to whether Hot Mix Asphalt (flexible) pavements are more economical or less economical over time, than Portland Cement Concrete (rigid) pavements. Even experienced state highway agencies and highway engineers disagree on the subject [9].

Nigerian has been undertaking massive development programs to eradicate the country’s poverty problems and to bring up the country to the level of middle income countries in 2025 G.C. Aware of the road infrastructure development as the backbone and the blood artery for all economic, social progress, due emphasis has been given to the implementation of the Road Sector Development program (RSDP) since 1997.

Initial cost is generally the major factor in deciding the type of the pavement in design. The planners often think that the flexible pavement is cheaper than the rigid pavements. In fact this is not always the case. In the last decade the price of bitumen which is the main ingredient of flexible pavement has increased because of the increase in crude oil prices.

Government executives frequently have to choose between concrete and asphalt paving materials for roads and highways. In the last few years in asphalt which caused a dramatic escalation in asphalt prices – reflected in a 250% increase during 2005-2008. It is likely that once the economic recovery gains traction, large shortages may reappear, oil prices will rise and asphalt prices will resume their upward climb. From 2003 to 2008 oil prices increased nearly 300%. During the same period, liquid asphalt increased 250%. The increases in asphalt prices during this period were not only a result of rising oil prices, but also by changes in oil refining practices which has led to a reduction in heavy crude production and reduced supply.

Global economic weakness has resulted in a 50% decline in oil prices during the past year. Despite reduced paving demand and lower oil prices, asphalt prices have declined only 12% from record high levels during the same period.

1.2                                               OBJECTIVE OF THE STUDY

The research work had been focused on the specific objectives to determine and compare the life cycle costs of rigid and flexible pavements and to investigate all other qualitative merits of rigid and flexible pavement.

1.3                                                   SCOPE OF THE STUDY

In this paper, the economic analysis has been done on both flexible and rigid pavements. These cost analyses play a great role on the decision-making stages in selection of pavement types. In this analysis initial cost of rigid and flexible pavements have been determined for both flexible pavements and rigid pavements according to design guideline.

1.4                                           SIGNIFICANCE OF THE STUDY

This study helps designers and builders to explore innovative and cost effective products to satisfy increasing demand that would economize the construction as well as increase durability.

It also help engineers to know the suitability of pavement depending on various parameters such as material, loading, longer life, cost effectiveness etc.

1.5                         DEFINITION OF FLEXIBLE AND RIGID PAVEMENT

Two types of pavements are laid in India-rigid pavement and flexible pavement. In simple terms, a flexible pavement can be defined as a pavement layer comprising of a mixture of aggregates and bitumen, heated and mixed properly and then laid and compacted on a bed of granular layer. Rigid pavements on the other hand, are made from cement concrete or reinforced concrete slabs, laid over a low strength concrete layer (Dry lean concrete, DLC) or on a well compacted layer of aggregates or both.

 

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