Effect Of Water In An Asphalt Road Pavement

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.