Wynand Jacobus Van der Merwe Steyn

Evaluation of selected effects of pavement riding quality on logistics costs in South Africa

The efficient operation of a countrys economy depends, among other things, on an efficient logistical system to ensure that goods can be transported efficiently between producers and users. The costs of logistics include aspects such as transport, storage, inventory, and management. Of these, the transport costs are directly influenced by the condition of the transport infrastructure. The effects of road riding quality on the costs of logistics were evaluated through analysis of data on actual truck costs (specifically, vehicle damage and maintenance) obtained from a logistics service provider as well as data on road riding quality for the routes used by the company. Analysis of the data indicated that the vehicle operating costs increased with decreasing riding quality (as would be expected). Spending adequate resources on the maintenance of routes in a country decreased vehicle fleet operating costs and ultimately the logistics costs of the country. It is recommended that the study be broadened to incorporate a larger sample of vehicles and road conditions.

Modelling of cohesion and adhesion damage of seal based on dynamic shear rheometer testing

Abstract Most current seal designs are based on the volumetric properties of materials and voids. In order to improve seal design, the possibility of introducing mechanistic principles into seal design was investigated. Introducing mechanistic concepts into seal design means that principles such as elasticity and viscoelasticity could be used in terms of stress-strain to explain phenomena such as damage in the seal structure. Two main failure parameters of seals – cohesion failure (fatigue cracking due to ageing of binder and loss of elasticity) and adhesion failure or stripping (occurring between stone to bitumen or bitumen to base) – are investigated using the complex modulus (G *) which is one of the viscoelastic parameters of bituminous materials. This paper therefore investigates the testing procedure of cohesion fatigue damage (CFD) and Adhesion Fatigue Damage (AFD) of bituminous seal material using the Dynamic Shear Rheometer (DSR). The CFD and AFD modelling are based on the stiffness reduction principle of materials under the action of cyclic stress. Based on the Lifetime Optimisation Tool (LOT) research programme from Delft University of Technology, a DSR testing procedure and approach was adopted for seals. The tests were performed on 70/100 penetration grade bitumen columns (for CFD) and on stone columns constituted with dolorite glued together with 70/100 penetration grade bitumen (for AFD). It was observed that the model for CFD depends more on stress, while the model for AFD appears to depend more on temperature. This observation agrees with the fact that adhesion damage is more sensitive to temperature change, whereas cohesion damage is more prone to be influenced by applied fatigue stress. The CFD and AFD models provide an indication of non-linear development of the accumulated fatigue damage of seal. This is represented by the modelling of the change of G *, as suggested in this investigation.

Evaluation of Sustainability of Low-Volume Roads Treated with Nontraditional Stabilizers

The use of nontraditional stabilizers to treat unpaved (mostly low-volume) roads has received attention over the past several years as various types of stabilizers have been developed and become available. Evaluation of the sustainability of various infrastructure actions, including the provision and maintenance of roads, is becoming more relevant as the effects of actions taken in the natural environment on itself and on the human environment are evaluated and understood in more detail. The Greenroads rating system offers a method for evaluation of the sustainability of the design, construction, and maintenance of roads. The system was developed with a focus on surfaced higher-volume roads. In this paper, the potential applicability of the Greenroads system for the evaluation of the sustainability of unsurfaced low-volume roads is investigated through two case studies of experiments in which unpaved low-volume test sections were treated with various types of traditional and nontraditional material stabilizers. Appropriate parameters were selected from the general Greenroads metric to ensure that those affecting unpaved low-volume roads would be evaluated (e.g., runoff quality and use of regional materials) while parameters such as paving emission reduction were excluded from the analysis. The assumption was made that all compulsory project requirements would be met by each of the options evaluated. It was concluded that the Greenroads metric can be used to evaluate the potential sustainability of unpaved low-volume roads treated with nontraditional stabilizers and that the metric can provide insight into the potential effect of various parameters on the sustainability of the various stabilization options.