INVESTIGATION INTO EARLY DETERIORATION OF SURFACE DRESSINGS IN GHANA

ABSTRACT
The success of bituminous surface dressing depends primarily on the adhesion of the chippings to the road surface. Premature failure of surface dressing in the country has become prevalent to the extent that some constructions begin to deteriorate soon after being in service. The overall aim of this research was to identify the possible causes of early deterioration of surface dressings in Ghana. The methods adopted for the study were: (i) examination of the existing local specifications for bituminous surface dressing, (ii) data collection through the use of a well-structured questionnaire to assemble empirical knowledge on surface dressing practices in Ghana, and (iii) visit to surface dressing construction site to assess construction practices. The study revealed that designers of the seal do not take into consideration the road surface temperature when specifying the binder viscosity. Also, not all the recommended tests are performed on the chippings by some of the contractors to ascertain aggregate conformity to the specifications. The study also established that rolling requirements were often ignored during construction and where rolling was carried out, sometimes the equipment used did not conform to specification. Because most of the contractors were not using electronic bitumen distributors and chipping spreaders, the possibility of inaccurate binder and aggregate application exist.

CHAPTER 1: INTRODUCTION 
1.1       Project Background
Bituminous surface dressing is a simple, effective and inexpensive road surface treatment for preserving the integrity of a road if adequate care is taken in its design and construction. Surface dressing is used in Ghana for both light-trafficked and medium-trafficked roads, and also as a maintenance intervention for trunk and urban roads. Bituminous surface dressing offers several advantages. If properly constructed, it provides an impervious, durable and safe road surface which allows road agencies to maintain a quality road network with a limited budget. As a maintenance technique, it allows the service life of a structurally sound road pavement to be extended if the process is undertaken at the right time using appropriate procedure. Under certain circumstances, surface dressing may also retard the rate of failure of a structurally inadequate road pavement by preventing the ingress of water and thus preserving the inherent strength of the pavement layers and the subgrade (TRL, 2000).

Of the approximately 68,053km of roads in Ghana as of 2010, about 12,332km or 18.12% were surfaced dressed (MRH, 2012). Construction and maintenance work on the road network in the country is generally undertaken by contracts managed by the road agencies, namely, the Ghana Highway Authority (GHA), the Department of Urban Roads (DUR), and the Department of Feeder Roads (DFR).

As surface dressing is very thin, it requires regular maintenance to quickly repair defects. Pavements with surface dressing are normally treated by resealing on a regular basis, usually every 6-10 years as part of a periodic maintenance program (MRT, 2005). Generally, however, some of the surface dressed roads in Ghana deteriorate earlier than expected making their investment cost ineffective.

1.2       Problem Definition
The success of bituminous surface dressing depends primarily on the adhesion of the chippings to the road surface. Factors such as inappropriate specifications, poor construction materials, and poor workmanship, can drastically reduce the service life of a bituminous surface dressed road. Critical monitoring of most surface dressed roads in Ghana reveals that there is early deterioration of such roads before the end of their design lives, and this must be investigated to establish the causes.

Factors that contribute to the failure of surface dressings are many and varied. These include poor pavement preparation, incorrect cutting back of the binder, wrong size of chipping used, incorrect binder application, delays in covering the binder, over or under spreading of chippings and wrong binder viscosity specified for the ambient temperature. Also, contractors usually abandon many surface dressing projects after the application of the primerseal without the sealing itself (either single or double). This causes the roads to deteriorate within the first few months, thus, having negative impact or effect on transportation and economy. Some of these negative impacts are reduction in ride quality of the road, increase in road user cost, unpleasant environment for those using and living adjacent to the road, and increase in road administration cost. But which of the many factors contribute the major causes of the premature failures of surface dressed roads in Ghana have not yet been documented.


At the moment, the causes of the premature failures are speculative lacking any empirical evidence. Unless the causes of the premature failures are well documented, it would be difficult to design intervention measures to right the problem. This study, therefore, sought to establish the factors which contribute to early deterioration of surface dressings in Ghana

1.3       Research Objective
The overall objective of this research was to investigate the possible causes of early deterioration of surface dressings in Ghana. The specific objectives of the investigation were:

Examination of the existing local specifications for bituminous surface dressings;

Evaluation of the conformity of the construction methods employed for surface dressings to the local specifications; and

Formulation of recommendations to improve surface dressing construction quality.

1.4       Scope of the Study
The scope of study entailed the following: 
Find out the design and specification for surface dressing project from the road agencies in Ghana and how the construction is supervised.

Enquire from contractors how construction of bituminous surface dressing is carried out.


Check the type of materials (chippings and bitumen) that are used and how they are applied.

1.5       Justification
Currently, no studies have been conducted to establish contractor knowledge and practices in the construction of surface dressing in Ghana. This study would provide

* documented evidence of the causes of the early deterioration.

* The outcome of the investigation would help avoid practices that cause early deterioration of surface dressings in order to achieve the desired service life, so as to

* minimize the life cycle cost of road construction and maintenance and road user cost.

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Item Type: Ghanaian Project Material  |  Attribute: 45 pages  |  Chapters: 1-5
Format: MS Word  |  Price: GH50  |  Delivery: Within 30Mins.
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