Conference Publications

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Analytical techniques to quantify modifiers in bitumen for the South African asphalt pavement industry
(2021-07) Makhari, A; Hawes, Nomashaka BN; Mturi, George AJ; Ojijo, Vincent O
Modifying bitumen is currently a common practice in South Africa. The asphalt pavement industry has seen an increase in use of different types of modifiers in an attempt to improve or extend the properties of bitumen. Common modifiers used in South Africa include plastomers (e.g. ethylene vinyl acetate or EVA), elastomers (e.g. styrene-butadiene-styrene or SBS) and warm mix additives (e.g. waxes). Bitumens are already complex materials which can be represented mechanically and rheologically with mathematical models. Recently, the need to also characterise the in situ structural and chemistry effect of modifiers within bitumen has been appreciated, in order to determine their influence on modified bitumen performance. This paper explores the analysis of bitumen with various modifiers using Fourier Transform Infra-Red (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC). Special attention is paid to quantification of these modifiers in bitumen as a quality control and forensic investigative tool, due to the current asphalt failure challenges facing the industry. The aim is to accurately determine the extent of modification through analytical techniques as a monitoring tool for the better construction of asphalt pavement roads. The paper shows such analytical scientific techniques have the potential to quantify locally used modifiers in South African bitumen.
Application of drones and image processing for bridge inspections in South Africa
(2021-07) Kemp, Lana; Roux, Michael P; Kemp, Mauritz J; Kock, R
In South Africa, visual inspections for all bridge structures are required every five years. A need was identified to establish if it would be practical to utilise technologies, such as drones and photogrammetry, to improve inspections and to reduce the cost of inspections. Drone and photogrammetry technologies are large components in the Fourth Industrial Revolution (4IR). For proof of concept, two bridges were inspected us-ing a drone. The drone inspection data captured for the two bridges was processed and point cloud models were created. These point cloud models were then used to estab-lish whether defects, identified on these bridges previously by way of regular TMH 19 visual assessments, could be identified from the point cloud models. The outcome of the study showed that it would be possible to use processed images from drone in-spections or other image capturing methods to inspect bridges and for monitoring pur-poses. The use of these technologies could improve the inspection methodology, not only of individual structures, but also of a network of structures as required by road au-thorities. Recommendations are made for future work.
Best practices in support of vulnerable road user protection in South Africa
(2023-07) Barnard, HC; Venter, Karien
Vulnerable road user fatalities continue to make up the bulk of road traffic related deaths in South Africa. Safe System-based measures aim to improve the safety of the road environment for all road users including vulnerable road users. Safe System-based measures are primary mitigation measures that focus on reducing the severity of accidents while supporting techniques and measures that focus on reducing the number of accidents. Road Restraint Systems (RRS) form a vital part of the road planning and design process in support of minimising the severity of accidents, including accidents involving vulnerable road users. The uptake of best practices relating to the provision of safe and forgiving roads that can mitigate the severity of injuries in South Africa, has been poor. This research paper considers the plight of vulnerable road users in the South African road environment and provides practical evidence/examples of existing scenarios where roadside risk for vulnerable road users such as non-motorised transport users can be addressed through the provision of correct and crash tested RRS that contribute to making the road environment inherently safe and more forgiving.
Bridge CNN defect prediction models using existing image data
(2022-11) Kemp, Lana; Roux, Michael P; Steyn, WJvdM
In South Africa, it is a requirement for all road agencies to conduct principal visual inspections of all bridge structures every five years. Smaller municipalities do not always have the necessary funds available for principal bridge inspections, resulting in either bridge inspections not being executed, or inspections being done by unqualified people. This paper intends to investigate the possibility of using existing bridge inventory and inspection image data to develop Convolutional Neural Network (CNN) models to predict and classify bridge defects autonomously. This research aims to improve the quality of bridge inspections and condition ratings assigned to defects to be more consistent and not reliant on human subjectivity. These models could ultimately be used for quality control in a Bridge Management System (BMS). The CSIR STRUMAN BMS contains inspection and inventory images captured during principal visual bridge inspections. As a proof-of-concept, bridge roadway joints were considered. 600 images of bridge roadway joints captured in the system were classified according to Defect and No Defect datasets. Different CNN classification models were developed to predict whether an image of a bridge roadway joint contained a defect or not. The image datasets were used to train, validate, and test the performance of the CNN models. The performance of the CNN models was evaluated using a Confusion Matrix and Classification report to select the best-performing model. In conclusion, the selected model was evaluated when introduced to new unseen images. The best performing CNN model utilised transfer learning and data augmentation to predict with 95% accuracy from images if a bridge roadway joint had a defect and with 65% accuracy if the bridge roadway joint had no defect.
Community perspectives as an essential element of resilience thinking: Resilience from a view of inequality
(2020-12) Dlamini, Sifiso B; Meyer, Isabella A
Resilience is a popular concept in development studies, particularly in research and development on how Information and Communication Technologies (ICTs) can be used to improve livelihoods. As much as the primary focus is on using ICTs to deliver services in sectors that operate in resource constrained environments, the question of inequality remains a key consideration. One of the challenges that faces the future of the ICT-related development of communities is the perspectives and perceptions of researchers on communities, particularly in developing countries with remote rural areas. Taking a resilience view on community without addressing the question of inequality leads to biased resilience strategies in the rural communities of developing countries. This paper presents thinking from an ongoing research study that aims to develop a resilience framework and guidelines for the introduction and use of mobile technologies in South African rural schools.
Conceptualising a benefit assessment framework for the South African National Roads Agency Ltd SOC research and development programme
(2021-09) Rust, FC; Sono, P; Van Dijk, G G; Fourie, H; Smit, Michelle A
In low-income countries Research and Development funding is limited and has to be invested with a view of optimum return, both economic return but also “softer” benefits such as human resource development. The assessment of these benefits is therefore important for the long-term sustainability of research and development programmes. Outputs from research and development in roads and transport are often not hard products aimed for the consumer market, but also include new design methods and techniques to enhance the performance of the transport system that cannot be easily quantified with benefit cost analysis alone. The article discusses the development of a framework for the monitoring of the performance of the South African National Roads Agency Research & Development Programme. The framework consists of a Balanced Score Card and a proposed set of indicators that address benefit throughout the innovation value chain.
Creating pathways to impact: Investing in supply chain and logistics capacity development in Africa
(2023-03) Grobbelaar, S; Meyer, Isabella A; Van Eeden, J; Vandaele, N; Van Wassenhove, L; Besiou, M; Decouterre, C; Rafter, S; Nolting, C; Dondofema, Richmore A
African logistics and supply chain management capabilities are essential to the performance of the continent's commercial and humanitarian supply chains. This study reviewed the challenges for researchers and practitioners in advancing logistics and supply chain performance through developing appropriate capabilities. A literature review and landscape mapping were followed by semi-structured interviews with 45 stakeholders from industry bodies, academia, funding bodies, consultants, specialists, and academics, confirming the capability and opportunity gaps in the current landscape. A meta-framework for sustainable institutional capacity development was constructed based on the empirical data that was gathered, and supply chain capacity development recommendations were proposed.
Developing a truck rollover risk calculator for South Africa
(2022-07) Ferreira, A; De Saxe, C; Steenkamp, Anton J; Nordengen, P
The Static Rollover Threshold (SRT) is an important metric for characterising a heavy vehicle’s inherent stability and risk of rollover. Current methods of assessing SRT include a tilt-table test and multi-body dynamics simulation which can be costly, time-consuming and often require significant technical expertise or technical vehicle data not normally accessible to the public. Simplified calculation methods exist, but a remaining challenge exists to reduce the required level of user expertise and input data to make the assessment useable by, for example, fleet insurers who would have an interest in SRT information. In this paper we investigate the use of simplified calculations prescribed by the New Zealand Land Transport Rule (NZLTR) and UNECE 111 as the basis for the development of a user-friendly SRT calculator. The calculation results were validated against a multi-body dynamics model using TruckSIM for the case of a rigid truck for a range of vehicle suspension and mass properties. The NZLTR and ‘interpolated’ UNECE 111 methods resulted in the smallest errors compared with TruckSIM, averaging 6-7% in absolute error over the 16 scenarios assessed. Maximum errors occurred when the ratio between drive axle and steer axle roll stiffness was at its highest (at a ratio of 4.7:1). The UNECE 111 method was then used as the basis for a Python-based SRT calculator tool. The tool demonstrates how pre-loaded technical vehicle data and logic can be used to minimise the required user expertise and hence make SRT calculation feasible by non-technical users in the fleet insurance industry in South Africa.
Difficulties monitoring short-term ageing in thin surfacing layers using asphalt concrete
(2024-07-20) O'Connell, Johannes S; VdM Steyn, WJ; Maina, J
Ageing has a profound effect on pavement performance, especially regarding cracking. Due to budgetary constraints, South Africa has pioneered the use of thin asphalt concrete layers. The research described in this paper is based on a short-term ageing study in South Africa, using data generated over a period of 6 years. During this time, polymer modified asphalt binders were increasingly employed in road construction, and rheological analyses from the dynamic shear rheometer were increasingly used to characterize asphalt binders. This study compared the complex shear modulus to the softening point as an ageing index property used to monitor the extent of short-term ageing of the recovered asphalt binder from newly laid asphalt concrete. The asphalt binder properties from 20 constructions sites were evaluated, whereby the recovered binder from the site shortly after construction was evaluated against the asphalt binder properties obtained in the laboratory after the rolling thin film oven treatment. The results indicate that the recovery process leads to a deterioration in the repeatability for the complex shear moduli obtained from recovered asphalt binders. The lower repeatability prevents meaningful conclusions from being made. Furthermore, the work shows that although the Rolling Thin Film Oven Test may be a good predictor of short-term ageing when using softening point as an ageing index property, it is only valid for unmodified asphalt binders in South Africa.
Evaluating the efficacy of laboratory ageing of asphalt mix binders as a prediction for field ageing
(2023-10) O'Connell, Johannes S; Maina, J; Bredenhann, SJ; Marais, H; Komba, J
A Performance-grade Binder Specification (SATS 3208) for South Africa was finalised after CAPSA 2015 and launched at CAPSA 2019. A key feature of the performance-graded binder specification is the regulation of binder performance after long-term ageing, which is simulated in the laboratory using the pressure ageing vessel (PAV). This paper reports how this simulated long-term ageing relates to the ageing of binders in continuously-graded asphalt surfacing mixes in the field. Samples of asphalt surfacing mixes were obtained from ten sites in Gauteng, South Africa, which were constructed 5 to 30 years ago and selected based on the availability of the original binders. An ageing profile was developed for the original binders by characterising their rheology in the original state, after rolling thin film oven (RTFO) ageing and pressure ageing vessel (PAV) ageing after 20 hours, 40 hours and 80 hours. The ageing profiles were compared to the corresponding recovered binders. Rheological parameters used for comparison were Softening Point and Flexural Creep Stiffness / m-Value from the Bending Beam Rheometer (BBR) test.
Evaluation of road condition indices methods used in South Africa and applicability for use in machine learning
(2024-07) Simelane, Melusi S; Rampersad, Ashiel
Road maintenance is a crucial process for pavement management systems. South African local roads are in critical condition, and their management is not at optimum level which is evident by their poor condition. The aim of the paper is to provide a machine-learning algorithm to assist road authorities to provide maintenance strategies. The objective of the study was to determine the most effective condition index for pavement management of flexible pavements. This is achieved by conducting descriptive and inferential statistical analysis of two case studies (Low volume roads and High volume roads). Statistical analysis indicated that the visual condition index (VCI has inconsistencies compared to the surface and deduct point pavement condition index (CISURF & CIPAVE) found in TMH 22. Four machine learning models were created, the model with a potential for deployment was a Gradient Boosting Classifier (GBC) model. The GBC model had an accuracy of 74 %, 85 % and 93 % in relation to the VCI, CISURF & CIPAVE respectively. The CISURF & CIPAVE was hence identified as the most effective index for use in flexible pavements
Heavy vehicle dynamic road wear from a rigid heavy vehicle when including road crossfall
(2021-09) Steenkamp, Anton J; Kienhofer, F; De Saxe, CC
Previous research investigating the dynamic road wear produced by heavy vehicles has not included the effect of road crossfall. This study shows that road crossfall, even at values as low as 1%, has a significant effect on the predicted dynamic road wear. A model of a rigid vehicle that includes rolling and pitching motion was developed for the analysis. The normalized 95th percentile aggregate fourth-power force is used as the road damage criteria. For the vehicle studied, a 24% increase in road damage is predicted for a crossfall value of 2% as compared to not modelling the crossfall, at a typical highway speed of 80 km/h and road roughness of 2 m/km. Road crossfall therefore plays a significant role in the dynamic road damage produced by heavy vehicles.
High-capacity coal trucks to reduce costs and emissions at South Africa's power utility
(2023-06) De Saxe, CC; Van Eeden, J; Kemp, Lana; Steenkamp, Anton J; Cowper, J
South Africa's national power utility, Eskom, is under growing pressure to increase its power generation capacity in the face of national rolling blackouts while also containing costs, increasing revenue, and reducing its environmental impact. While the entity embarks on an ambitious $ 10 billion 2050 decarbonisation plan, there are short-term opportunities to save costs and emissions in parts of its business through relatively simple interventions. In this work, we investigate the transport of coal to Eskom's power stations. We focus on the approximately 30 million tonnes transported by road, where ‘high-capacity vehicles’ (HCVs) have already demonstrated significant productivity improvements in a national pilot project in South Africa. First, the current costs and emissions associated with the current transport activity are calculated, which amount to approximately ZAR 4 billion (US$250 m) and 230,000 t of CO2 respectively per year. A case is then presented for transitioning the coal transport fleet to 74-t high-capacity vehicles, which is calculated to save Eskom up to ZAR 248 million (US$15 m) and 35,000 t of CO2 each year. In addition, we show that the more road-friendly HCV fleet would result in a reduction in road damage valued at ZAR 50 million (US$3 m) per year. Ultimately, these cost figures represent savings to the South African taxpayer, as both Eskom and the road authorities are state entities. The precise cost benefit to Eskom, however, will depend on the nature of its coal supply contracts with local mines and transporters, but it is likely that market forces will enable these savings to be realised throughout the supply chain.
The improvement of the operational efficiencies in the minibus taxis industry: A work in progress system dynamics approach
(2023-07) Rathogwa, Mashudu
The Minibus Taxi Industry is plagued with violence, un-roadworthy and unsafe vehicles. Although the government has made numerous efforts to formalize and regulate the sector, the industry remains unregulated and unofficial. As the industry is not properly integrated into South Africa's public transportation infrastructure, this impacts the operational performance of minibus taxis. Nowadays, there is intense competition between those with operating licenses and those without. To ensure that the industry functions in accordance with South African law and to prevent organized violence within the industry that endangers commuters, substantial police action is required. This paper presents the work-in-progress of a study that aims to use Systems Dynamics as a tool to advise on what can be done to formalise and regulate the minibus taxi industry in order for it to participate fully and formally in the country's public transport system in order to improve the operational performance of the industry.
Laboratory evaluation of alternative cost effective pavement materials
(2021-07) Smit, Michelle A; Akhalwaya, Imraan; Rust, FC
The South African road network is severely impacted by the high costs associated with upgrading, maintaining and constructing road infrastructure in conjunction with the shortage of good quality construction materials. The Council for Scientific and Industrial Research (CSIR) has conducted extensive research on an innovative, cost-effective bituminous stabilising agent known as Nano-Organosilane Modified Emulsions (NMEs). These emulsions allow road engineers to design stabilised base and subbase layers using marginal materials which are normally considered unusable for road construction. For the purpose of determining the potential performance of NMEs, extensive advanced laboratory evaluations have since been conducted, most recently in the form of triaxial testing. This paper outlines the results and findings from both monotonic and dynamic triaxial testing conducted on NME materials, and draws correlations with Heavy Vehicle Simulator (HVS) test results. Compared to standard materials and designs, the initial results on the use of NMEs as a stabilising agent in road bases and subbases has since showed excellent performance and cost savings. The key results in this paper conclude that NME materials: Exhibit strong-cohesion as observed from monotonic triaxial testing as well as from test-pit samples cored from HVS test-sections at Provincial Road D1884; Have significant potential for improved long-term pavement performance, based on laboratory measured resilient moduli in conjunction with back-calculated field-moduli on NME test-sections; Display very low susceptibility to Permanent Deformation (PD) including rutting; and Justify being considered as a sustainable and environmentally friendly alternative to traditional pavement materials and designs.
Microbial Induced Calcium Carbonate Precipitation (MICCP) for road construction
(2022-07) Smit, Michelle A; Akhalwaya, Imraan; Rust, FC; Ramdas, Veshara
The growing concern over climate change has led the drive for the development of alternative building materials in several industries, including road construction. Bio-based construction, using Microbial Induced Calcium Carbonate Precipitation (MICCP) has been investigated in recent years as a potential cost-effective and environmentally friendly alternative engineering approach. The Council for Scientific and Industrial Research (CSIR) developed a research program looking at MICCP. Several barriers to using MICCP in road construction was found, a potential biohazard using exotic bacteria and the current technique used for treatment. In this paper, in situ cultivation of indigenous urease positive bacteria was investigated and compared to a CSIR designed biological prototype. The objective of this paper is to present the results of Unconfined Compressive Strength (UCS) tests performed on a marginal G5 (COLTO, 1985) material treated with the prototype and in situ cultivated bacteria. The work showed that it was possible to cultivate urease positive bacteria present within the G5 material. It was found that the cementation solution could act as a stimulation and cementation media when the pH is reduced to give the bacteria time to cultivate and buffer the pH upward for Calcium Carbonate Precipitation to take place. Lastly, the CSIR prototype performed better in terms of UCS and treatment technique. The treatment consists of only one application of the prototype, which is more consistent with current road construction practice, as compared with the multiple application needed for in situ cultivation.
Operating costs: PBS vs conventional heavy vehicles in South Africa
(2021-07) Steenkamp, Anton J; Venter, Karien; De Saxe, Christopher; Kemp, Lana
Road transport is a highly competitive industry and is renowned for low profit margins. Road transport however accounts for almost 6 % of the Gross Domestic Product (GDP) and is the backbone of the economy. The Performance-Based Standards (PBS) or Smart Truck Pilot project has existed in South Africa since 2007 and monitoring data has shown substantial savings including a 34 % reduction in crash rates, 18.3 million litres of fuel and 534 840 trips being saved since the start of the project. The Australian PBS programme is projected to save more than AUS$17 billion by 2034. The potential financial impact of PBS in South Africa has not yet been fully quantified using actual operational costs from operators participating in the trial. In this study a questionnaire was used to collect operational costs from PBS operators and has compared the costs of PBS and baseline vehicles. The most significant finding is that on a per tonne-km basis, the weighted average overall cost savings was 18.8 % for the all PBS versus baseline vehicles. Not all PBS operators showed a reduction in operating costs but this could be attributed to having only one PBS vehicle and operating in a specialized industry with short lead distances. PBS however, appears as a viable solution to reduce transport costs, reduce crashes and emissions and also save the road infrastructure and should be considered for regulated implementation in South Africa.
Proposed methodology of optimizing the secondary public transport network of a city in demand
(2023-07) Rathogwa, Mashudu; Singano, Afika P
In 2019/20, it was of major importance to identify an alternative network within the Integrated Public Transport Network (IPTN) that can meet the increasing population demands. Being composed of high-capacity corridors, the current IPTN still requires a secondary network to meet day to day transporting needs (City of Joburg, 2019). Since the city's land isn't utilized very densely, the main network only serves a small part of it. High-capacity modes may service the primary network. The secondary network is necessary to support the primary network. The capacity of the secondary network is far lower than the city's real demand for public transportation. The majority of public transportation journeys cannot be accommodated by the primary network. This is because they are built on roads that don't work as well and aren't good for high-capacity technologies like Bus Rapid Transit (BRT). The secondary network provides services in places where it would be too expensive to set up and run the primary network. The smaller buses and minibus taxis that make up the secondary network have fewer seats. For example, while the primary network requires 365 000 seats during peak hours (assuming a seat utilization rate of 60%), the secondary network requires approximately 2 million seats during peak hours (City of Joburg, 2019). This paper explores using the traveling salesman method to identify and analyze the secondary network that meet the current demands.
Relating the rheology of recovered binders from asphalt surfacing in the field to their fatigue performance
(2024-10) O'Connell, Johannes S; Maina, J; Bredenhann, SJ; Marais, H; Komba, J
G*.Sind and TC are two of many rheological parameters that have been proposed as potential specification properties for control of fatigue performance for hot mix asphalt. This paper assesses the extent of correlation between the values of these parameters and the presence of cracking in the hot mix asphalt surfacing from 11 sites carefully selected to represent a wide range of fatigue performance over periods ranging from 5 to 20 years. The binders were recovered using a modified Abson recovery process that accurately represents the properties of the aged in-situ binder. Results indicate that TC correlates better with the condition of the asphalt surfacing, compared with G*.Sind. The results also demonstrate that although binder fatigue parameters may be an indicator of fatigue performance, the actual fatigue performance is also determined by other factors such as binder film thickness of the mix, traffic loading, climate and rate of ageing.
South African infrastructure condition - an opinion survey for the SAICE Infrastructure Report Card
(2021-06) Rust, FC; Wall, K; Smit, Michelle A; Amod, S
The South African Institution of Civil Engineering (SAICE) Infrastructure Report Cards of 2006, 2011 and 2017 reported that much of the South African infrastructure is in a poor condition. To augment the recent 2017 Report Card, a survey was, for the first time, conducted amongst SAICE members to obtain their opinion on the condition of infrastructure (in terms of a grading), the trend of the condition over time, as well as the reasons for the individual's grading. The 669 respondents indicated that, apart from a few exceptions such as national airports and the Gautrain, much of the infrastructure is in a poor state, which is very similar to the results obtained from the SAICE Report Card process. The results were also analysed per province and indicated that, in the opinion of respondents, specific provinces in particular are struggling with poor infrastructure. The main reasons given for the poor infrastructure were a lack of maintenance, lack of institutional capability, lack of sufficient funding and over-loading of infrastructure.

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