Investigating the Effect of Axle Loading on Crack Initiation of Bituminous Pavements in Uganda.

Abstract

Road transport is the most dominant mode and plays a pivotal role in supporting the economic and social development of the country. Road transport carries over 90 percent of country’s passenger and freight traffic. Of the national roads, 4,157 km are paved while 16,388 km are unpaved (MoWT, 2017). The national roads, which make up only 30 percent of the network, carry 80 percent of the total road traffic. Overloading on the national road network continues, thereby resulting in deterioration of the network and the need for additional finances to rehabilitate damaged roads. About 60% of the infrastructure budget has been dedicated towards upgrading gravel roads to bituminous roads. However, despite the efforts in upgrading the roads, failure to maintain existing bituminous roads in time has led to a reduction in the paved road asset value by about 10% annually (MoWT, 2017). This is partly due to failure to detect paved road deterioration in time, which starts from cracking. This research was carried out to investigate the effect of Axle Loading on Crack Initiation in Bituminous Pavements in Uganda. Traffic counts were determined manually and the traffic volume was converted into Equivalent Axle Load. The road roughness conditions of the road was estimated using he MoWT field check list in which the roads were rated. It was determined that, for Sentema road, with an Axle Loading of 4.4 MESALs, longitudinal cracking would start as soon as it’s open to traffic. For Kulekana road, with an Axle Loading of 0.3 MESALs, structural cracking starts after approximately 4.1 years (4 years and 36 days). However, if the mix design was such that it had more bitumen (about 10% more bitumen), then the initiation of cracking would be delayed by 2.3 years (2 years and 108 days). For Kevina road, with an Axle Loading of 0.25 MESALs, structural cracking starts after approximately 3.9 years (3 years and 324 days). However, if the mix design was such that it had more bitumen (about 9% more bitumen), then the initiation of cracking would be delayed by 2.4 years (2 years and 144 days).