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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.

Surface morphology of lead deposits from H2SiF6-PbSiF6 electrolyte containing an animal glue was investigated by means of the periodic galvanostatic electrolysis and SEM-EDS observation. The weight average molecular weight of the glue was also determined with the static light scattering measurement. The temporal changes of the overpotential and the weight average molecular weight were discussed in terms of the elapsed time after preparing the electrolyte which contained 100 g∙L−1 of H2SiF6 and 100 g∙L−1 of Pb(II) and in which the initial concentration of the glue (Cglue) was 0–10.0 g∙L−1. The dendritic growth of lead deposits was observed from the electrolyte of Cglue = 0 g∙L−1 in the galvanostatic electrolysis where the cathodic current density and the electrolyte temperature was −150 A∙m−2 and 40 ℃, respectively. Smooth and dense lead deposits were obtained in the electrolyte of Cglue = 0.5–5.0 g∙L−1 when the elapsed time τ = 0 d. The surface of the deposits gradually became rough with increasing τ in the electrolyte of Cglue = 0.1–1.0 g∙L−1. On the other hand, nodules or bearded deposits were observed on the deposits obtained in the electrolyte of Cglue = 5.0 g∙L−1 when τ = 1–2 d. After this, the surface became smooth with the further increase of τ. The change of the weight average molecular weight of the glue (Mr,w) with τ was described with the equation, 1/(Mr,w)τ = 1/(Mr,w)0 + k′τ, in the electrolyte containing 100 g∙L−1 of free H2SiF6 and 100 g∙L−1 of Pb(II) at 40 ℃. The k′ value was evaluated to be 5 × 10−9 min−1 in the electrolyte of Cglue = 1.0 g∙L−1 and 6 × 10−9 min−1 in the electrolyte of Cglue = 10.0 g∙L−1.

The mechanism of contact between liquid droplets and hot surfaces is important and attracts many researches recently. Herein, we experimentally investigate the contact of Newtonian and viscoelastic droplets between gradually heated surfaces at low Weber numbers, which has not been explored. To present a detailed analysis of contact line dynamics, experiments were performed across a surface temperature ranging boiling conditions to above Leidenfrost temperature (100°C−300°C), while various impact phenomena with increasing surface temperature have been observed for Newtonian and viscoelastic droplets. We demonstrate that the polymer additives significantly affect the dynamic contact angle and contact radius on heated hydrophilic surface. In the Leidenfrost regime, the increased velocity causes considerable reduction on contact time of water droplets, especially at the breaks-up mode. However, it does not influence the contact time of impinging polymer droplet. Aqueous polymer droplets with high molecular weight and high concentration suppress secondary atomization, splashing and break-up, but promote droplet foaming and the generation of viscoelastic filaments. The results illustrate how the polymer additives, surface temperature and impact velocity affect the impact outcomes, and original impact phase diagrams are proposed finally.

The paper has analyzed influence of additives representing a group of thermoplastic elastomers and complex thermoplast-based modifiers on fatigue life of asphalt concrete. Regularities in time have been determined in the paper and close values of their physical and mechanical properties have been obtained while using various types of binders and modifiers. Statistic and laboratory investigations have made it possible to obtain theoretical parameters of the fatigue life for materials used for road dressing. The analysis has been based on statistical values of ordinary and modified asphalt concrete and asphalt concrete mixes of C- and A-type obtained during the experiments for the period from 2010 till 2016. A statistic analysis has permitted to compare a parameter Ипл (resistance index to plastic deformations) with such parameters as ny (number of elastic constraints) and Rc (threshold structural strength). 12 calculations (Nos. 1–12) have been carried out in order to realize targets of the second investigation. Calculative characteristics of asphalt concrete required for determination of reliability parameters have been estimated in the paper. A bottom layer of twoor three-coat pavement has been selected as an object of the investigation due to the fact that it is more often subjected to an impact of cyclic tensile stresses caused by a transport load. The required value for calculation of tensile stresses s at calculated temperature 0 has been accepted on the basis of executed estimations while using finite elements method and distribution of stresses has been determined along structure with 20 cm thickness due to load А2. Corresponding conclusions have been made in accordance with the obtained results.

The pressure-viscosity coefficient, α, is a measure of the pressure dependence of the viscosity of the liquid in elastohydrodynamic lubrication (EHL). There seems to be confusion around the understanding of the pressure-viscosity response in the inlet zone. In this paper the values of α were obtained from measurements of viscosity as a function of pressure and offers a understanding on the piezoviscous effect at various inlet pressures for those liquids. Moreover, the viscosities of several commercial engine oils and laboratory blends of mineral and synthetic base oils with polymer additives were measured at pressures up to 1 GPa and at temperatures of 40°, 75°, and 100°C. It was observed in some of these materials The significant changes within viscosity are temperature- and pressure-dependent. Analysis of the experimental results indicated that the solidification (significant increase viscosity) is due to liquid-solid phase transitions occurring in the lubricant's polymer additives. Thus, this paper gives evidence on the role of molecular weight and concentration of polymer and its influence on the pressure and temperature-dependent onset of the phase transitions. This transition has not been discussed in the open literature and is not accounted for in current bearing design using the Barus equation or the modified Yasatomi equation and may be the cause of some bearing damage modes.

On the basis of the V. K. Stokes micro-continuum theory, the effects of couple stresses on the nonlinear dynamic response of the unbalanced Jeffcott’s flexible rotor supported by layered hydrodynamic journal bearings is presented in this paper. A nonlinear transient modified Reynolds’ equation is derived and discretized by the finite element method to obtain the fluid-film pressure field as well as the film thickness by means of the implicit Euler method. The nonlinear orbits of the rotor center are determined by solving the nonlinear differential equations of motion with the explicit Euler’s scheme taking into account the flexibility of rotor. According to the obtained results, the combined effects of couple stresses due to the presence of polymer additives in lubricant and the pressure dependent viscosity on the nonlinear dynamic response of the rotor-bearing system are significant and cannot be ignored or overlooked. As expected, these effects are more noticeable for polymers characterized by higher length molecular chains.