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.
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.
For more Civil Engineering Projects Click here
===================================================================Item Type: Ghanaian Topic | Size: 45 pages | Chapters: 1-5
Format: MS Word | Delivery: Within 30Mins.
===================================================================
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.