Comparative Performance Analysis of Selected Sections of Lahore--Islamabad Motorway ((M--2)

Abstract

Pakistan is country which constitutes a huge network of roads and this network is constantly increasing. Due to the lack of the periodic maintenance the condition of the roads are not very impressive. Some of the roads do not even complete their design life due to poor construction methodologies or incompatible design or job mix formula (JMF). The pavement design in Pakistan is based on AASHTO design guide and Marshall Method is generally used for the mix design. Both these methods are empirical in nature and are developed for the environmental conditions of USA, however these design methodologies are used in different parts of the world. In flexible pavements of Pakistan, the two main distresses are Rutting and Fatigue Cracking. Motorway (M-2) has generally performed very well after the construction was completed in 1997. However, some sections of the motorway are subjected to rutting and fatigue cracking and at the same time some sections have performed very well. This study is based on forensically analyzing the selected good and bad sections of M-2 to compare their results and to find the causes of rutting and fatigue cracking in Bad section. The analysis is based on the destructive testing of the pavement. In addition to the conventional testing, this study includes performance testing of both good and bad sections of the pavement. Stability and flow, moisture susceptibility by tensile strength ratio test (TSR), Indirect tensile fatigue test (IDFT) and resilient modulus test were performed on the cores recovered from site. The experimental results were analyzed statistically in Minitab to spot the significant differences in values. The resilient modulus values for Asphaltic Wearing Course of selected bad section showed that the material was susceptible to rutting as compared to the material of asphaltic wearing course of selected good section and analysis of variance (ANOVA) proved the same. The indirect tensile fatigue test (ITFT) elaborated that the wearing course of selected bad section failed after significantly less number of load cycles as compared to the wearing course of selected good section. The moisture susceptibility by tensile strength ratio (TSR) showed that both asphaltic wearing course and asphaltic base course of selected bad section were highly moisture susceptible. So the experimental and statistical results showed that the selected bad xiv  section was susceptible to rutting, fatigue cracking and moisture induced damage. The main reasons for the distresses was high percentage of asphalt content, low stiffness and high percentage of air voids.