Imraan Akhalwaya | University of Pretoria (original) (raw)

Conference Papers by Imraan Akhalwaya

Southern African Transport Conference (SATC 2022), CSIR International Convention Centre, Pretoria, South Africa, 4-7 July 2022., 2022

The growing concern over climate change has led the drive for the development of alternative buil... more 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.

Virtual Southern African Transport Conference (SATC 2021), CSIR International Convention Centre, Pretoria, South Africa, 5-7 July 2021., 2021

The South African road network is severely impacted by the high costs associated with upgrading, ... more 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.

6th International Conference on Accelerated Pavement Testing (APT 2020), Nantes, France, 27-29 September 2021., 2020

The Council for Scientific and Industrial Research (CSIR) has conducted several research studies ... more The Council for Scientific and Industrial Research (CSIR) has conducted several research studies associated with understanding the behavioural characteristics and performance of new innovative pavement structures stabilised with Nano-Organosilane Modified Emulsions (NMEs). These pavement structures could play a significant role for local road agencies in South Africa as they may be utilised as a cost-effective alternative to conventional road designs, thus reducing economic constraints and road maintenance backlogs. Since 2017, a series of Heavy Vehicle Simulator (HVS) tests have been conducted on several road sections across South Africa, most notably on Gauteng Provincial Road D1884 in Meyerton and on Gauteng Provincial Road K46 near Diepsloot. Both these road sections consist of bespoke designs that incorporate NME base and subbase layers. The aim of this paper is to present performance results as obtained from these HVS tests. It is anticipated that these results will provide a good indication of the potential benefits and risks of using NME materials as opposed to using costly imported crushed aggregates, which are typically required for conventional South African road designs. These HVS results in conjunction with previously published laboratory data conclude that NME pavement layers exhibit exceptional performance, thus prompting the need for quicker standardisation and implementation of NMEs across South Africa.

Conference on Asphalt Pavements for Southern Africa (CAPSA 2019), Sun City, South Africa, 13-16 October 2019, 2019

This paper describes the findings of a Heavy Vehicle Simulator (HVS) test on road D1884 in the Ga... more This paper describes the findings of a Heavy Vehicle Simulator (HVS) test on road D1884 in the Gauteng province of South Africa. The pavement structure was rehabilitated using an anionic nano-silane modified bitumen emulsion stabilising agent in the base and sub-base. The rehabilitation design traffic loading (20 year design period) is based on 3 million Equivalent Standard 80kN Axle Loads (ESALs). The 50 year old pre-rehabilitated road exhibited severe distress with in-situ materials in the upper pavement layers that have weathered to a tested G8 quality-materials usually considered unsuitable for use in base/sub-base layers of a pavement structure. The HVS test subjected the pavement structure to an equivalent of at least 3.5 million ESALs (using calculated damage factors). Using the standard damage factor of 4,2, 7.5 million ESALs were applied. Although the dual wheel load was increased to 80 kN and water introduced (in depth as well as on the surface), no structural failure could be induced during the test (a final rut of only 8 mm was measured). The in-situ stabilisation of available materials using an anionic nano-silane modified bitumen emulsion compared with the standard approach of importing high quality materials realised a saving of 43%. The HVS test was conducted on a site where materials of "unacceptable" quality stabilised with a laboratory proven technology were used. This provided road authorities with quick results for the consideration of the future use of this technology which potentially embodies the cost-effective service delivery of high-quality roads.

Rubberized Asphalt Rubber Conference (RAR 2018), Protea Hotel Marriott Kruger Gate, Kruger National Park, South Africa, 25-28 September 2018.

Crack reflection on roads with cemented layers is a significant problem worldwide and can lead to... more Crack reflection on roads with cemented layers is a significant problem worldwide and can lead to premature failure. Innovative road materials such as bitumen-rubbers possess the potential to successfully retard crack reflection, thereby minimizing damage to roads from water ingress. The research work conducted on bitumen-rubbers in conjunction with the knowledge generated on the retardation of crack reflection has led to several developments and innovations for the road industry. One such innovation is the development of the Crack Activity Meter (CAM), a device capable of measuring horizontal and vertical crack movements simultaneously. The CAM has been successfully used in conjunction with the Heavy Vehicle Simulator (HVS) during several accelerated pavement tests of road sections containing bitumen-rubber materials. Results from various laboratory investigations in conjunction with these field tests spans over decades of research into aspects such as crack movement monitoring, fatigue testing of bitumen-rubber asphalt and their performance under varying environmental and loading conditions. This paper provides a historic overview of the research conducted at the CSIR relating to the use of bitumen-rubber materials to successfully retard crack reflection. The paper additionally discusses the initial history, developments and early laboratory work conducted on the performance of bitumen-rubber materials in South Africa. Finally the paper identifies gaps in research in line with current day trends and developments that may be explored further for new methods of improving the successful retardation of crack reflection.

Southern African Transport Conference (SATC 2018) and International Conference on Transport Infrastructure (ICTI), CSIR International Convention Centre, Pretoria, South Africa, 9-12 July 2018., 2018

Nano-modified emulsions (NMEs) have recently been used successfully across a number of trial proj... more Nano-modified emulsions (NMEs) have recently been used successfully across a number of trial projects in South Africa. Following the development of initial draft design approaches for NME stabilising agents, the Council for Scientific and Industrial Research (CSIR) has decided to evaluate these technologies more extensively by means of an independent laboratory-based research investigation. The aim of this paper is to present the initial results of this investigation, comprising an initial desktop study and a preliminary laboratory evaluation on NME materials in comparison to standard bituminous stabilised materials. The laboratory tests conducted form part of an extensive laboratory evaluation that may be used to verify existing preliminary material specifications for NME materials as well as correlate future test results obtained from Heavy Vehicle Simulator (HVS) tests on several NME demonstration sections. Nano-modified materials consisting of varying mineralogies are investigated using standard laboratory tests, with comparisons being made relative to materials enhanced with standard bitumen emulsion. Based on the results illustrated in this paper, various interpretations and correlations were made between the desktop study and the laboratory evaluation in terms of general trends expected and observed. The laboratory results conclude that NME materials perform significantly superior to standard bituminous stabilised materials, which may have direct implications for improved cost-effective pavement design alternatives. This paper additionally provides initial observations and limitations encountered during the treatment and laboratory testing of these materials, and these are presented together with recommendations being made, regarding the performance and use of NMEs as innovative stabilising agents for road infrastructure.

Journal Papers by Imraan Akhalwaya

Taylor & Francis Online: International Journal of Pavement Engineering, 2020

Upgrading, maintenance and rehabilitation of road infrastructure is expensive, especially in view... more Upgrading, maintenance and rehabilitation of road infrastructure is expensive, especially in view of the growing scarcity and cost of suitable road building materials. In areas with high mica content and secondary minerals such as smectite in the natural materials, stabilisation with cement is not viable. The Council for Industrial and Scientific Research of South Africa has embarked on a research programme to evaluate the performance of substandard materials improved with anionic nano-silane modified bitumen emulsions for use in base and subbase layers. This work comprises laboratory testing as well as Accelerated Pavement Testing using the Heavy Vehicle Simulator (HVS). The results of a full-scale HVS test on a light pavement as well as initial analysis on a medium traffic road are discussed. It has been shown that stabilisation of available substandard materials using an anionic nano-silane modified bitumen emulsion compared with the standard approach of importing high quality crushed aggregate can lead to savings as high as 40%–50% for equivalent performance. In addition, there was also a significant reduction in construction effort and time.

Papers by Imraan Akhalwaya

International Journal of Pavement Engineering, 2020

Lecture Notes in Civil Engineering, 2020

Paper presented at the Southern African Transport Conference (SATC 2018), 9-12 July 2018, CSIR In... more Paper presented at the Southern African Transport Conference (SATC 2018), 9-12 July 2018, CSIR International Convention Centre, Pretoria, South Africa

Paper presented at Rubberized Asphalt Rubber 2018 (RAR2018), Kruger National Park, Protea Hotel, ... more Paper presented at Rubberized Asphalt Rubber 2018 (RAR2018), Kruger National Park, Protea Hotel, South Africa, 25-28 September 2018

Presented in: 12th Conference on Asphalt Pavements for Southern Africa, Sun City, South Africa, 1... more Presented in: 12th Conference on Asphalt Pavements for Southern Africa, Sun City, South Africa, 13-16 October 2019

Books by Imraan Akhalwaya

The Sustainability Handbook: Volume 03, 2021

The development of the local end-use market for waste plastic is crucial to increasing South Afri... more The development of the local end-use market for waste plastic is crucial to increasing South Africa’s plastic recycling rates, especially for low-value, problematic plastic fractions, such as polyolefins consisting mainly of polyethylene and polypropylene. The use of recycled and/or alternative materials such as plastics in road construction is beneficial not only in terms of sustaining the environment, since naturally occurring materials will be conserved but as a means of reducing construction costs. Recycled plastics are being investigated worldwide not only as a green investment, but also for improved pavement durability (Milad et al., 2020). The objectives of the study were to screen, evaluate and implement existing international technologies in line with South African design standards and specifications for materials in road construction. The main research question was whether low value
waste plastics can be optimised as alternative road construction materials in South Africa.

Conference Presentations by Imraan Akhalwaya

Conference: CSIR Emerging Researcher Symposium (ERS), CSIR International Convention Centre, Pretoria, South Africa, 28-29 June 2018., 2018