Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 4(2):194-200 (ISSN: 2141-7016) 194 Laboratory Assessment of Highways Asphalt Bitumen in Southwest of Nigeria I. Akiije and V. A. Moyinwin Department of Civil and Environmental Engineering, University of Lagos, Lagos, Nigeria Corresponding Author: I. Akiije ___________________________________________________________________________ Abstract This paper reports laboratory tests conducted while evaluating some properties of bitumen used in the production of hot mixed-hot laid asphalt of three different asphalt plants in southwest of Nigeria. The bitumen properties investigated included determination of the purity or contamination of the bitumen sample. Determination of the temperature at which bitumen sample used will attain standard fluidity for the purpose of mixing with aggregate. The bitumen properties also investigated included determination of the sample grade at the temperature of 25°C and 60°C. These properties were investigated through Solubility, Softening Point, Penetration and Saybolt Viscosity tests respectively. Although all the three asphalt plants samples passed the Softening Point and the Solubility tests but could not satisfy the specification values set up as standards for Penetration and Saybolt Viscosity tests. Southwest of Nigeria is in the tropical region and the standard specification values for Penetration test should be AC 60/70 but the results obtained are of about AC 85/100 that is meant for temperate climate regions. It is pertinent to note that the harder the grade of bitumen, the lower the penetration value and the better its use for the production of quality asphalt in tropical region. The significance of this study is that results of experiments on bitumen samples from the three selected asphalt plants in southwest of Nigeria are unsatisfactory when related to the expected standard approved grades of both Penetration and Saybolt Viscosity tests. Unsatisfactory results from Penetration and Saybolt Viscosity tests as shown in this study could significantly affect the performance of asphalt leading to the premature failure of flexible pavements as presently prominent in southwest of Nigeria. __________________________________________________________________________________________ Keywords: solubility, softening, penetration, viscosity, flexible, pavement INTRODUCTION Bitumen in this study is referring to asphalt cement, a binder in the production hot mixed-hot laid asphalt of flexible pavement. A mixture of bitumen from fractional distillation during the refining petroleum crude and non-volatile oil such as propane, butane or pentane by heating can produce graded bitumen of usable consistency for flexible pavement Wright (2003). Bitumen is usually graded in accordance with its viscosity or penetration at a specified temperature, Kadyali and Lal (2008), Garber and Hoel (2010). Bitumen is useful in the production of asphalt primarily because of their excellent binding or cementing power and their waterproofing properties, as well as their relatively low cost, Adedimila (2000). Asphalt is a relatively thin high quality bituminous surface material on top of series of granular layers of a flexible pavement, Akiije and Oyekan (2012). A flexible pavement is a structure that maintains intimate contact with and distributes loads to the subgrade and depends on the interlock, particle friction, and cohesion for highway stability. Highway is a system which its functions allow for traffic movement in six recognizable stages of main, transition, distribution, collection, access and termination AASHTO (2008). Hot mixed-hot laid asphalt is usually produced by properly blending bitumen, coarse aggregate, fine aggregate, and filler (dust) at temperatures ranging from about 80°C to 165°C. The surface of flexible pavement varies depending on the type of bitumen used and climatic conditions. Flexible pavement distresses do occur where unsatisfactory bitumen properties manifested in the asphalt used for a highway. Distress is defined as an indication of unfavourable pavement performance or signs of impending failure, or any unsatisfactory performance of pavement sort of failure Oguara (2006). Too much bitumen in asphalt can cause distortion. Pavement distortion is any change of the pavement surface from the original shape inform of rutting, corrugation, shoving and depressions. A rut is a longitudinal surface depression which may develop in the wheel paths. Corrugation is a form of plastic movement typified by ripples across the bituminous pavement surface that occurs usually at points where traffic starts and stops. Corrugations are usually caused by lack of stability of asphalt layers in warm weather or lack of aeration of Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 4(2): 194-200 © Scholarlink Research Institute Journals, 2013 (ISSN: 2141-7016) jeteas.scholarlinkresearch.org