Description
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
When it comes to paving, Asphalt material is the most popular because of it its
quality features it has such as looks good, lasts long, and is generally low
maintenance. Moisture damage can be defined as the loss of strength and
durability in asphalt mixtures caused by the presence of water. Moisture damage
is induced by the loss of bond between the asphalt cement or the mastic and the
fine and coarse aggregate. Moisture damage accelerates as moisture permeates
and weakens the mastic, making it more susceptible to moisture during cyclic
loading.
Historically, six contributing mechanisms have been identified associated with
moisture damage: detachment, displacement, spontaneous emulsification, pore
pressure induced damage, hydraulic scour, and the effects of the environment on
the aggregate–asphalt system. However, it is to be mentioned that moisture
damage is not limited to a single mechanism but is the outcome of a combination
of these mechanisms (Little and Jones, 2003). Santucci and Aschenbrener (2003)
have identified the following factors that contribute to adverse effects of water in
asphalt pavement. Finally, moisture damage mechanisms results in the following
distresses like, Stripping, Bleeding, Rutting, Corrugation and Shoving, Cracking,
Raveling, Localized failures.
Water damage can be defined as the loss of strength and durability in asphalt
mixtures caused by the presence of water. Water damage is induced by the loss of
bond between the asphalt cement or the mastic (asphalt cement, the mineral
filler and small aggregates) and the fine and coarse aggregate. Water damage
accelerates as moisture permeates and weakens the mastic, making it more
susceptible to moisture during cyclic loading. Finally, Water damage mechanisms
results in the following distresses.
Stripping: Debonding of aggregates and binder at the bottom of HMA layer.
Bleeding: Formation of asphalt binder film on the pavement.
Rutting: Surface depression along wheel path.
Corrugation and Shoving: Plastic movement typified by ripples or
an abrupt wave across the pavement surface.
Cracking, Water Bleeding and Pumping.
Raveling: Progressive disintegration of HMA layer.
Localized failures: Progressive loss of adhesion between binder
and aggregates or progressive loss of cohesion in aggregates and
in binder.
This work discuses all these deterioration in full and at the end solution for the
these problems were analyzed. In this chapter one we discussed the introductory
part of the work, chapter two presents the background and review of the
related studies, chapter three describes the methods applied, chapter four
discusses the results of the methods used, chapter five summarizes the research
outcomes and the recommendations.
1.2 PROBLEM STATEMENT
For a better understanding of water effect on pavement deterioration, it’s the
need to correctly identify the problem and isolate issues of contributing factors
like material variability and construction practices. To this end, current study is
intended to discuss the mechanisms associated with water induced damages in
pavement. In order to fulfill this objective, this paper addresses following issues:
Identification of the problem.
Fundamental concepts- binder and aggregate interaction and representative
failure mechanisms.
Test methods to characterize moisture sensitivity.
1.3 AIM AND OBJECTIVE OF THE STUDY
The aim of this work is to study the effect of water on pavement made of
asphaltic material. At the end of this study the student involved shall be able:
i. To analyze the effect of water in asphalt pavement
ii. To analyze the solution to such effects
iii. To analyze methods used in repairing the deterioration
iv. Identify moisture-related damage in asphalt pavement
v. Describe various methods to make asphalt pavements less susceptible to
moisture damage and understand the steps to address moisture damage
taken by state highway agencies
vi. Discuss a cost-benefit analysis performed to determine the applicability of
anti-strip additives
vii. Discuss the existing research related to asphalt moisture damage and
identify gaps.
1.4 SCOPE OF THE STUDY
When cracks form in asphalt, it allows for water to seep under the surface, which
is damaging to the base beneath. Each time it rains and this happens, the
weakness, damages, and pavement deterioration rate increases. This damage is
often not visible from above, but the damages being caused are serious and can
be costly to fix.
1.5 PURPOSE OF THE STUDY
The main purpose of this work is to Provide a practical discussion of moisture
damage in asphalt pavements.