ResearchSpace :: Browsing by Author "Mgangira, Martin B"

Browsing by Author "Mgangira, Martin B"

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Aeolian sands as material to construct low-volume roads
(National Academy of Sciences, 2011-07) Paige-Green, P; Pinard, MI; Mgangira, Martin B
Aeolian sands are widespread in many semi-arid to arid areas of the world and often provide the only economic source of construction materials for low volume roads. Experience in southern Africa over a number of decades has shown that provided aeolian sand materials are correctly selected and constructed, they can make effective subgrade, subbase and base layers for low volume roads. Research into their use has shown that the use of standard geological (sedimentological) techniques for classification allows the differentiation of sands that will perform well or badly as road base and subbase materials. The technique uses the Phi classification system allowing the sands to be defined by their mean particle size and the standard deviation about this mean. The paper describes simple techniques for assessing the suitability of these materials for use and innovative construction methods for their utilization. The results obtained during monitoring of various roads also indicate the benefits of well-compacted sand subgrades.
Characterization of pavement distress from test pit observation
(2009-08) Mgangira, Martin B
The characteristics of the roadbed material are critical to the overall performance of the pavement. The paper presents examples with discussion of the form of distress experienced within the pavement layers, based on observations made during the profiling exercise of an investigation into the causes of the premature failure of a pavement. The field investigation entailed a detailed inspection and recording of the profile exposed in test pits, with particular attention being paid to areas with cracks, noting their positions and extent within the pavement layers. The focus of the paper is on the observed orientation of crack propagation within the pavement layers. It is shown that the crack propagation is not always in the vertical plane. This has implications in dealing with crack sealing procedures. The causes of the observed distress were attributed to the behaviour of the roadbed as it experienced fluctuating moisture conditions.
Compressive strength of a concrete mix for pavement blocks incorporating industrial by-product
(www.satc.org.za, 2017-07) Mokoena, Refiloe; Mgangira, Martin B
Concrete block paving for roads has been proposed as part of a concept on sustainable infrastructure. In an effort to respond to sustainability and environmental awareness, the use of industrial by-products has been employed in the mix design of the concrete for a block paving system. This contributes towards preservation of natural resources as waste materials from industrial processes are used. Class F fly ash obtained from a coal power station in Vereeniging in South Africa was used for the study. Compressive strength tests were done on concrete cubes containing varying fly ash contents from 0% to 90% as replacement for cement by mass. A decrease in compressive strength and increase in workability was observed with increasing fly ash content. A decrease in water requirement while still producing a workable mix compared to the conventional concrete was also observed with an increase in fly ash content. This would also contribute to the ecological footprint by decreasing the water demand for mixing. The optimal mix from the initial laboratory experiments contained 50% fly ash and exhibited a compressive strength of 37.3 MPa at 28 days.
Design and manufacturing of an aggregate abrasion test device for testing in high acceleration field
(2021-11) Xungu, Sipho; Mgangira, Martin B; Giani, John C
This paper describes the design and manufacturing of a mechanical system, the Aggregate Abrasion Test Device (AATD), which comprises of a rolling model drum, with the purpose of obtaining experimental data that is subsequently used to quantify the abrasion behaviour of aggregate particles. The study of the abrasion behaviour of geomaterials is complex due to among other factors, non-linear mechanical properties that depend on stress levels and stress history. In this case the aggregate assemblage is subjected to different stress levels by operating the system within the geotechnical centrifuge environment. The system was tested up to a maximum gravitational force of 25-G. The paper focuses on the design, manufacturing, construction, testing of the system and the experimental lessons or findings observed during the prototype testing. The system provides an alternative experimental way for determining the durability of the aggregate solely dominated by particle-to-particle interaction mechanism.
Establishing miniaturised structural testing techniques to enable high-throughput screening of microorganisms and microbial components for unpaved road stabilisation application
(Elsevier, 2020-01) Malapermal, Veshara; Naicker, Prisha; Mgangira, Martin B; Mukaratirwa, Samson; Lalloo, Rajesh; Ramchuran, Santosh O
Roads are expensive to develop particularly in challenging environmental conditions, and a lack of understanding of the properties of soil can lead to poor design and premature failures contributing to costly maintenance. The construction industry is exploring new opportunities involving biological processes and products to modify the structural properties of the in situ material, in terms of strength, volume stability, durability and permeability. Through an integrative interdisciplinary approach several microorganisms and other existing bio-enzymatic products such as secondary metabolites, enzymes, endospores, and extracellular polymeric substances have been considered as possible alternatives to conventional methods for the development of sustainable road infrastructure. Limitations in the current state of technology to developing bio-based solutions include microorganism selection and the ability to evaluate derivative components in rapid structural tests that enhance the time to development of proper commercial products. This study focused on the testing of fermentation derived components of biological materials in a high-throughput manner, using miniaturised structural tests to validate screening and selection methodology. The methods tested included resistance to abrasion, resistance to erosion, water absorption and resistance to compression load. Unique miniaturised test equipment was successfully developed using computer-aided design (CAD) and 3D printing technologies. Effects were measured to enable the rapid evaluation of a target microorganism and for screening of biological components or fractions. Results obtained using a Bacillus isolate reported in the current study exhibit strength characteristics and can potentially be formulated as a product for soil stabilisation. This work forms the basis for in vitro selection methodology to enhance development of bio-based structural materials for application in the road sector.
Evaluation of damage to a road and sports complex on expansive clays
(2008-08) Mgangira, Martin B; Paige-Green, P
The paper discusses a road rehabilitation project and a sports complex, where the underlying in situ materials were typical African black cotton soils known for their expansive characteristics. Field investigations were undertaken to discern the main causes of the pavement distress and the serious damage to roads and structures encountered at a large complex with the support of quantitative data from test pits and with laboratory test results. In addition, available design documents and construction records were reviewed to identify key aspects that may have contributed to the observed excessive cracking of the road pavement and damage to both roads and structures at the sports complex. The results of the investigations indicated that the in situ materials were both potentially highly active. It was concluded that either inadequate precautionary measures were taken against heave during the design phase, an indication of the lack of appreciation of the behavior of expansive clay, or that poor supervision and control during construction and commissioning negated many of the design innovations
Evaluation of the effects of enzyme-based liquid chemical stabilizers on subgrade soils
(2009-07) Mgangira, Martin B
The purpose of this study was to asses the strength of enzyme treated soil material. Thus the aim of the paper is to present laboratory results on the effects of two enzyme-based liquid chemicals as soil stabilizers. Soil samples were prepared for standard geotechnical tests from two types of soils treated with the two enzyme-based products. One soil had a plasticity index of 35% and the other had a plasticity index of 7%. The maximum plasticity index reduction after treatment of both soils was less than 5 % and therefore not significant. A slight improvement in the maximum dry density was obtained following treatment by one product on one of the soil samples, but this is within experimental variability. Unconfined compressive strength was evaluated after the samples were left to cure in plastic bags for 7, 14, 28 and up to 56 days for one sample and revealed a mixed effect on strength. In those instances where there was an increase in strength it was less than 50 % with an increase in concentration level of the two enzyme-based stabilizers and age for both soils after treatment, which is practically not significant.
The influence of ballast fouling on track settlement
(2018-07) Rampersad, Ashiel; George, Theresa B; Mokoena, Refiloe; Mgangira, Martin B; Gräbe, PJ
The contamination of railway ballast (referred to as ballast fouling) is commonly caused by ballast particle degradation, external debris fouling due to surface spillage and clay fouling due to subgrade pumping. Intrusion of these fines in the ballast layer can impede rapid drainage which is necessary for good track performance. There is little research relating both fouled ballast and track settlement in a South African context. This paper discusses the effect of coal contaminated ballast on track settlement by use of a large scale “box test” apparatus. A series of tests was conducted on ballast aggregate, typically used on heavy haul railway lines in South Africa, with varying percentages of coal dust material (0, 8.4, 16.9, 25.3 and 33.8 % by weight of aggregate). Testing was conducted at 10 Hz for 100 000 cycles with a moisture content of 5.0 %. Results indicated an increase in settlement of between 11.7 and 40.2 % per 10 % increase in coal dust contamination. It is envisaged that this research will aid the South African railway industry in identifying the critical levels of coal fouling which will hence contribute towards reducing maintenance costs as well as improving railway safety and network reliability.
An investigation of aggregate degradation in a high stress field
(2018-07) Mgangira, Martin B; Xungu, Sipho A; Giani, John C
The deterioration of the aggregate material used in road construction is of concern as it affects the overall long term stability of the road pavement and should be minimised by using durable aggregates. The paper presents proof of concept of an experimental system, developed to assist in the evaluation of aggregate quality, using a customised rolling model drum, in which the aggregate assemblage is subjected to different stress levels by using the geotechnical centrifuge modelling technique. The outcome of the study has demonstrated the operation and functionality of the system and the potential to quantify aggregate durability solely dominated by particle-to-particle interaction mechanism.
Investigation of the effects of type of crusher on coarse aggregates shape properties using three-dimensional Laser Scanning Technique
(ASCE, 2016-07) Komba, Julius J; Mgangira, Martin B; Mohale, L
The fundamental shape/morphological properties of coarse aggregates including form, angularity, and surface texture are known to influence the performance of pavements. The coarse aggregate shape properties are affected by many factors, amongst others, the properties of the parent rock and the type of crusher or crushing operations. Therefore, quantification of the effects of the crusher type on the aggregate shape properties is important as it influences the bulk properties of pavement materials and therefore performance. Recent studies have demonstrated that laser scanning technique can be employed to better quantify the three-dimensional (3- D) shape properties of aggregate materials used in pavements. In this paper, the shape properties of quartzite aggregates crushed by using four different types of crushers were investigated. The results have demonstrated the extent to which the aggregate shape indices computed using laser scan results can be used to distinguish aggregate by-product from different crushers.
Laboratory assessment of the influence of the proportion of waste foundry sand on the geotechnical engineering properties of clayey soils
(South African Institution of Civil Engineering, 2006) Mgangira, Martin B
Soil improvement can be achieved through mechanical stabilisation using industrial byproducts. Clayey soils were blended with waste foundry sand to examine its influence on the geotechnical engineering properties of the soils. The waste foundry sand was first subjected to standard geotechnical engineering testing. The effect of the foundry waste sand on the modification of the plasticity, swell potential, compaction characteristics and CBR values of the soils is demonstrated in this paper. The results show that the addition of waste foundry sand improves the performance potential of otherwise marginal materials for use in geotechnical engineering applications.
Laboratory capacity building and skills development for a newly established road research centre
(2018-10) Lwanda, V; Kagombora, J; Digaga, A; Magafu, FF; Mgangira, Martin B
Africa Community Access Partnership (AfCAP) is supporting research activities in Africa region. One of the projects supported by AfCAP in research activities was to build capacity and implement a laboratory skills development programme for laboratories of the Local Government Infrastructure and Transportation Research Centre (LoGITReC) in Tanzania. Laboratory capacity building efforts included human resources development, establishment of laboratory quality assurance procedures, basic laboratory work inventory system and equipment procurement. Development of general operational protocols which would provide guidance for the everyday general technical administration of the laboratory. The capacitation of the laboratory was aimed at providing capability to support the execution of the research programme. Staff at the LoGITReC laboratory and three other regional laboratories were the beneficiaries of the capacity building project. The paper highlights experiences as expressed by LoGITReC (the beneficiaries) on the capacity building programme. A positive contribution to skills development is evident and as a result of the establishment of the laboratories, increased access to testing facilities for materials used in rural road works in Tanzania has been realised.
Measurement of shape property distributions of quartzite aggregate from different crushers using 3D laser scanning system
(Transportation Research Board (TRB), 2016-01) Mgangira, Martin B; Anochie-Boateng, Joseph; Koen, Renée; Komba, Julius J; Tutumluer, E
Aggregate shape properties are used to characterize aggregate product from quarry operations. However, aggregate shape depends on rock type and crushing process. A meta-quartzite, a relatively low grade thermal metamorphic rock was crushed through four crushers. In this paper, a description is provided on the quantification of particle shapes using data from a 3-D laser scanning device. The images from the laser were fully utilized in quantifying the shape descriptors in order to identify the differences between individual aggregates. It was possible to quantify differences in particle shape characteristics at the small particle scale and aggregate shape distributions between the different types of crushers and possible influence of particle sizes as well as interaction effects. Aggregate products vary significantly according to the nature of their processing. For all the shape parameters, a statistically significant difference was found between the four different crusher types. For some of the shape parameters a statistically significant difference was also found amongst the particle sizes.
Microstructural pavement material characterization: some examples
(Southern African Transport Conference (SATC), 2008-07) Mgangira, Martin B
The utilisation of advanced measurement techniques should assist in the characterization of pavement materials at a micro-scale. The motivating factor for such an approach is that material properties at the micro-level have a critical role in the way materials respond to loading at the macro-level. The objective of the paper is to demonstrate how Scanning Electron Microscopy (SEM) as an example of advanced measurement techniques was used for material characterization. A range of samples of pavement engineering materials were examined at a micro-scale using the technique. Selected examples of material characterization are presented. The potential application of microstructural material characterization for the identification of key elements which provide the opportunity to understand fundamental behaviour of pavement engineering materials is demonstrated
Performance evaluation of bio-based fractions derived from Bacillus spp. for potential in situ soil stabilisation
(2022-02) Ramdas, Veshara; Lalloo, Rajesh; Mandree, Prisha; Mgangira, Martin B; Mukaratirwa, Samson; Ramchuran, Santosh O
Current and future research focuses on the use of renewable technologies and materials to stabilise weak soils, of varying degrees, for road construction applications. Soil stabilisation is a method of strengthening a natural soil to meet this purpose. Our interest is in the use of bio-based components, derived from microbial growth processes, that contribute to the needed desirable strength characteristics for in situ soil stabilisation. This investigation focuses on novel Bacillus-based stabilisers obtained from the vegetative and spore growth stage. In this study, eighteen bio-based components were derived from a Bacillus licheniformisfermentation and extracted into various aqueous and non-aqueous fractions for strength property assessment. The strength properties of the treated soils (i.e., dolerite and weathered granite soil) were assessed via previously developed lab-scale equipment to rapidly pre-select the best performing fractions, (i.e., compression stress, erosion, abrasion, and water absorption tests). The effect of one superior performing prototype (a) was validated at large-scale, using standard erosion and abrasion tests (i.e., whole broth at 1.8% stabiliser concentrations), and showed resistance to abrasion (3.37 ± 0.03%) (p value = 0.0001) and resistance to erosion (33.20 ± 0.15%) (p value = 0.001). The elemental composition and microstructure of the bio-stabilised soil was determined using energy dispersive X-ray spectroscopy and scanning electron microscopy, respectively. This evaluation formed part of the selection of the best performing Bacillus derived fractions and achieved a proof of concept for the next phase of product prototype development. This study demonstrated a novel bio-mediated approach to the overall criteria for evaluation and selection of candidate product prototype/s, for stabilisation of two varying soils, and for potential application in road construction works.
Premature distress of a pavement on expansive black cotton soil in the Horn of Africa
(2008-11) Mgangira, Martin B; Paige-Green, P
This paper discusses a typical example of the distress experienced by a flexible pavement constructed over black clay soil, also commonly known as black cotton soil, where minimal precautionary measures were implemented. Black cotton soils are generally recognized as expansive soils and change significantly in volume with changes in the moisture condition due to wetting-up and drying-out during the wet and dry seasons respectively. The volume changes lead to differential deformation which then induces distress and leads to damage of the pavement constructed on such soils. By way of example the paper describes an investigation of a road in the Horn of Africa in an area with extensive deposits of the black clays, demonstrating the importance of correctly characterizing these soils prior to the pavement design and taking appropriate counter measures against expected movement of the roadbed that will cause damage to the pavement
Quantification of aggregate grain shape characteristics using 3-D laser scanning technology
(SATC 2013, 2013-07) Mgangira, Martin B; Anochie-Boateng, Joseph; Komba, Julius J
Aggregate shape and surface characteristics influence the performance of both bound and unbound pavement materials. This paper presents some results of an on-going study on the characterization of aggregates using a three-dimensional (3-D) laser scanner technology. A sample of coarse aggregate andesite particles passing 19.0 mm and retained on 13.2 mm sieve was used for the study. The 3-D images from the laser scanning device were fully utilized in quantifying the shape descriptors in order to identify the differences between individual aggregates. It was possible to quantify differences in particle shape characteristics at the small particle scale. The study has demonstrated the advantages of the innovative 3-D laser scanning technology to quantify the shape characteristics of aggregate particles.
Quantifying effect of stress levels on aggregate degradation using an abrasion test in a model rotating drum
(2019-10) Mgangira, Martin B; Sambo, A
This paper presents the results of a study of aggregate particle degradation by quantifying changes to aggregate particle shape due to different levels of applied stress. Proof of concept of the experimental system, developed to provide some insights into aggregate degradation solely due to particle-to-particle interaction mechanism is introduced. The aggregate particle degradation process is created within a customised rolling small model drum, in which the aggregate assemblage is subjected to different stress levels created through simulated increased gravitational forces by testing in the geotechnical centrifuge. The aim of this study is to establish consistency of the experimental system with expected results on the influence of stress levels on aggregate degradation. This is achieved through the quantification of the number of generated fines. The determined generated fines show consistency with expected results of the influence of stress level on the degradation of quartzite, fresh and weathered aggregate samples and therefore validating the experimental system.
Quantifying the environmental impacts of a sustainable concrete mix for a block paving system
(Cape Town: Alive2Green, 2024-01) Dumani, Nozonke; Mokoena, Refiloe; Mgangira, Martin B
A sustainable concrete mix design, incorporating industrial by-products: fly ash and recycled plastic pellets, was developed, and optimized through laboratory performance-based testing trials. The primary objective of this investigation was to offer environmentally sustainable alternatives to conventional concrete mixes that can be used for concrete block paving and aligns with circular economy principles and fosters enhanced employment opportunities and poverty reduction. Following a laboratory investigation to optimise the quantities of fly ash and plastic pellets in the concrete mix, paving blocks were produced in the laboratory using the optimised mix. The blocks were also tested to ensure compliance with performance criteria stipulated in national specifications for concrete block paving. This chapter focusses on the comprehensive life cycle assessment (LCA) conducted to investigate the environmental impacts associated with the production of the optimised concrete mix design in comparison with two references mixes. All three mixes comprised varying quantities of cement, fly ash as a partial cement replacement, and plastic pellets as a partial substitute for sand. The analysis included concrete with 100% Portland limestone cement, concrete with 50% Portland limestone cement and 50% fly ash, and concrete with 50% Portland limestone cement, 50% fly ash, and plastic pellets. The study, limited to a cradle-to-gate analysis, utilized the life cycle assessment software tool SimaPro 8.1 with the Ecoinvent Database version 3. The life cycle inventory dataset for each material was compiled, and the CML-IA Baseline World 2000 method was employed to generate and report the results. The LCA study results demonstrated that adding fly ash as a cement substitution significantly reduced the environmental impacts of concrete mixes. However, the extent of this reduction depended on the type of allocation method used. Under no allocation and economic allocation scenarios, concrete mixes with fly ash exhibited lower environmental impacts than those without fly ash. Conversely, mass allocation scenarios indicated higher environmental impacts for concrete with added fly ash more than 35%. Additionally, it was noted that environmental impacts for fly ash concrete mixes with plastic pellets as a partial substitute for sand were marginally higher than those with fly ash concrete mixes using only sand.
Review of current and future bio-based stabilisation products (enzymatic and polymeric) for road construction materials
(2020-10) Malapermal Ramdas, Veshara; Mandree, Prisha; Mgangira, Martin B; Mukaratirwa, S; Lalloo, Rajesh; Ramchuran, Santosh O
In situ soil modification is required in order to improve the primary engineering properties of the material to meet a road construction standard. Bio-stabilised soil is an environmentally friendly, cost-effective alternative to imported granular fills, concrete, costly hauling of materials or export to a landfill. In-service soil performance and required maintenance is highly dependent on methods of stabilisation, ranging from expensive mechanical stabilisation to chemical processes. As such, many alternative materials originating from bio-based sources are being explored as potential stabilising additives to improve weak subgrade soils (i.e., dispersive, erodible and collapsible soil, and soft or expansive clays). Some key solutions include the use of bio-derived enzymes, microbes, and polymeric additives to avert road failure caused by water penetration and/or erosion. The role of microbial substrate specialisation has been largely unexplored, since the level of research done on alternative stabilisers consists mostly of small ad hoc studies. In addition, research has focused on a reduction in permeability and an increase in compressive strength using enzymes and polymers, however, the complexity of these products and their implementation for a wide range of soil types and structural applications remain limited. Currently there is a need for more supporting research methodologies and systematic approaches on the implementation of bio-based materials for infrastructure development. This also includes the simplification of bio-based products for potential construction applications. This review provides (a) an overview of soil stabilisation techniques, (b) the primary challenges that lay ahead for future research in bio-based stabilisation products application in the road sector and (c) innovations to address the challenges of using modernised techniques in the road construction industry (i.e., weak subgrade and the required maintenance thereof, as well as the development of potential bio-based additives for unpaved road construction application).

Browsing by Author "Mgangira, Martin B"

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