ABSTRACT
One of the major obstacles to Nigeria's techno-economic development has been a lack of good road infrastructure. Despite a large deposit of natural bitumen in the form of semi-liquid and bitumen sand, the reliance on imported bitumen/asphalt for road construction and maintenance in Nigeria has reduced road coverage and quality. To use local bitumen as a binder in pavement construction, an efficient upgrading process is required using polymers, nanomaterials, and other chemical additives. However, the selection of an appropriate modifier depends on many factors including the origin, elemental and chemical composition of bitumen. This review presents vital properties of Nigerian bitumen extracted from oil wells and tar sands with the view to identifying potential additives as solutions for its upgrading. Based on predefined selection criteria, we conducted a systematic review of the literature. We gathered information on the current state of knowledge about the major issues encountered during the polymeric modification of bitumen. In addition, data on existing practices used by various road researchers to address such issues was gathered. Effort was made to review waste packaging polymers and plastics for possible utilization to ensure sustainable pavement infrastructure in Nigeria. The results of this review showed relatively little information on Nigerian bitumen upgrading. Many authors have investigated different polymer additives on asphaltic bitumen sourced from different countries and the results has pointed to the capability of polymeric modification to improve some of the properties of bitumen. A knowledge gap however, exists in the optimization of polymer dosage, and characterization of bitumen at the SARA level to aid the understanding of the effects of polymeric modification and mechanisms involved during the pavement degradation. Additionally, it has been challenging to generalize the effects of different polymers due to the variation of bitumen properties from different sources. This review identifies the potential for upgrading Nigerian bitumen using polymer additives, the potential of waste plastics, crumb rubbers, and packaging waste materials as alternative and sustainable additives also highlighted.
