Causes of Defects of Asphalt Pavement and Its Remedies A Case Study In Agaro Town

Abstract

Asphalt pavements provide an excellent material for roadways when designed and constructed properly and deliver a smooth, quiet, and durable solution. However, the success of any asphalt pavement is dependent on the paving material being designed for its environment, construction methodology, and drainage and work man ship. Based on the level of accuracy achieved by various approaches and tools available, frequent design defects, discrepancies and work redundancy are obvious in road design project which ultimately leads to damages and deterioration. Due to those mentioned problems, the government and road user in general is suffering from loss of huge sum of money due to pavement damages and deterioration The objective of this Study is to examine the Causes and remedial measures for asphalt concrete pavement damages. It is also intended to compare the engineering properties of the existing pavement layers with the standards and finally, recommendations on how to address possible problems associated with the different types of pavement damages and deterioration. The study was conducted in Agaro town a route from “Bulbulo Kebele - KoyeBer” cover around 15km length. Based on the existing theories and principles this research study addresses the general objectives to investigate the causes of asphalt concrete pavement failures and its remedial measures. For this planned purpose, the samples from sub grade, sub bases, base course and asphalt layer disturbed samples were collected from the worst road failure location of the road. The study used both primary and secondary data. The secondary data were obtained from various published and unpublished sources of the governmental and the non-governmental organization. The primary data were obtained through field survey and condition surveying, and laboratory analysis. During condition surveying some localized pavement distresses like shoving, potholes, alligator cracks, block cracks, edge cracks, longitudinal cracks, ravelling ,rutting and poor drainage condition were observed. The average thickness of each layers were measured and Asphalt 3.95cm, Base 13.37cm, and Sub base 19.25cm. From field investigation and laboratory test result the AASHTO and Unified soil classification are Sub grade A-7&MH, sub base A-2-6&GM and base course A-2-4 & GW, Atterberg limits parameters Average LL, and PI in percent were base course (4,4), sub base(27,12.99) and sub-grade(54,20.5) and compaction, MDD g/cc and OMC% were base course(2.7,6.21), sub base(1.83,9.67) and sub-grade(1.61,14.64), CBR% were base course 145.9%, sub base 84.7% and sub-grade10.1% obtained, Bitumen content Non-damaged asphalt 4.97%, BH1=3.12%, BH2=2.64%,BH3=2.16% and BH4=2.29% Based on the laboratory test result and condition survey the following are cause of pavement damages; Sub grade soil, degree of compaction, pavement material thickness, improper bitumen content and Poor drainage. Finally surface treatments, Fill cracks with asphalt emulsion slurry, Fulldepth patching, removing vegetation close to the ditches are some of the recommendation forwarde