Study On The Expressway Construction Technology For High Modulus Asphalt Mixture Base Course In Addis Ababa-adama, Ethiopia

With the rapid development of global economy, the economy in African area is also in rapid development, but its current situation of sparse road network and poor road traffic seriously restricts the development of economy and the improvement of people’s livelihood, therefore most of the roads in this area are in urgent need of renovation or reconstruction, and the road grade of national highway network in many African countries is gradually developing from soft soil road and flexible asphalt-treated surface pavement to flexible asphalt concrete pavement which yields good economic returns, has long service life, and requires no or little maintenance during operation period. Whereas, based on the current development trend and research & test results of flexible asphalt concrete pavement, the adoption of flexible pavement with high modulus asphalt concrete base course, which is characterized by better resistance to rutting and load transmission, longer service life, lower overall construction cost and shorter construction period, exactly provides this area with a shortcut to rapidly relieve the imminent traffic pressure.Relying on the project construction of Addis Ababa(capital)-Adama Toll Motorway in Ethiopia(hereinafter referred to as "Addis Ababa-Adama Toll Motorway"), this paper mainly studies and summarizes the construction technology of motorway high modulus asphalt concrete base course which is applicable to the climatic and traffic features in Ethiopia. As this technology is applied in African area for the first time, the technical basis of this research is based on the domestic research experience on this technology and the domestic current technical specifications and test regulations of motorway construction, etc. In the research, firstly, an inspection was made on the raw materials such as aggregate and asphalt actually used for Addis Ababa-Adama Toll Motorway, which determined that the performance of all preliminarily selected raw materials could meet the requirements of project implementation. Secondly, in order to seek the high modulus agent meeting the technical performance of high modulus asphalt mixture and the optimal mixing amount of high modulus agent and to optimize the construction cost of high modulus mixture, this research also included Marshall experiment, rutting test and other comparison and selection tests over multiple high modulus agents under the condition of optimal asphalt-aggregate ratio, as well as the comparison and selection on construction performance and economy, and finally selected the high modulus agent and its optimal mixing amount for project implementation. Afterwards, design and verification of target mix proportion and production mix proportion were performed in allusion to the requirements for mixture in project implementation, which thereby proved a lot of laboratory conclusions about the superiority of high modulus asphalt mixture to other admixture-modified asphalt mixtures in the aspects of high-temperature rutting resistance, residue stability ratio, freezing-thawing split-strength, failure stiffness modulus, aging resistance, etc. And then a 200m-long subgrade was selected for trial pavement test of HMAC-25 high modulus base course, based on which the large area construction of HMAC-25 high modulus base course of Addis Ababa-Adama Toll Motorway was carried out. During the construction process, appropriate adjustment was made to part of construction parameters according to the actual conditions on the site, and self-inspection and sampling inspection were conducted on all road performance indexes successively, and the construction technology of high modulus base course was finally determined.Based on the research and summarization of the construction process of Ethiopia Addis Ababa-Adama Toll Motorway high modulus base course support engineering, it verifies that the rutting resistance and water stability of high modulus asphalt mixture are greatly improved with the addition of high modulus agent, the construction technology is simple and easy to operate, all testing results of the engineering reach the expected target and meet the current demand of pavement development to improve road network in African area; meanwhile, a large number of construction and production control parameters during the implementation process of raw material selection, mix proportion design, mixture blending, transportation, paving and rolling, etc. of high modulus asphalt mixture are summarized through the implementation of the Project and the relevant researches, certain practical experience is hereby acquired, and more preferable experience is accumulated for popularization and application of high modulus asphalt concrete pavement in African area, domestic development of asphalt pavement technology, and development of asphalt pavement in other countries and regions.