ResearchSpace :: Browsing by Author "Mvelase, Gculisile M"

Browsing by Author "Mvelase, Gculisile M"

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Advanced and automated laser-based technique to evaluate aggregates
(International Road Federation, 2011-11) Anochie-Boateng, Joseph; Komba, Julius J; Mvelase, Gculisile M
The Council for Scientific and Industrial Research (CSIR) is undertaking a research project to investigate the use of laser-based scanning technology to quantify the morphological/shape properties (i.e., form - flatness, elongation and sphericity; angularity; surface texture) of aggregates used in pavements and railway ballast. To date, no automated method is available for direct measurements of shape properties of these materials in Africa. The objective of this paper is to present a three-dimensional laser scanning technique to determine flatness, elongation and sphericity of aggregates used in South African roads. A three-dimensional (3-D) laser scanning device was used to obtain the dimensions, surface area, volume, and subsequently, compute flat and elongated ratio of six different aggregate samples. The results were compared with the standard manual method that is currently used by the road industry to quantify aggregate shape properties. It is expected that, this study would influence decisions to improve aggregate material characterization and pavement design.
Effect of round particles on shear strength properties of railway ballast
(2016-07) Mvelase, Gculisile M; Anochie-Boateng, Joseph; Msibi, LL
The railway industry in South Africa is facing a problem where passage of trains on the heavy coal haul lines are causing degradation by means of wear (roundness) of ballast materials, and consequently, leading to differential track settlement and unevenness of the surface. Railway ballast remains an important component material in a rail track structure system. However, their fundamental attributes of shape have not been determined accurately, and quantitatively related to the performance of the tracks in a more rigorous and scientific way. This paper presents a case study of five ballast materials used by Transnet Freight Rail heavy coal line in South Africa. The objective is to investigate the effect of ballast particle roundness determined from a modern three-dimensional (3-D) laser scanning technique on the internal frictional angle of the ballast materials. The results indicated the effect of ballast shape on shear strength, as fresh ballast from the quarry provided higher internal frictional angle when compared with ballast that have been degraded and rounded. It was established that there is a strong relationship between frictional angle and roundness (i.e. shape) of the ballast materials and a pebble sample that was used as a control material for extremely rounded ballast.
Investigation into flat and elongated particles ratio for asphalt mix design using a modern laser technique
(2019-07) Anochie-Boateng, Joseph; Mvelase, Gculisile M
Flat and elongated particle ratio is a shape characteristic for coarse aggregates used in pavements. The ASTM D 4791 is the standard test method to determine flat and elongated coarse aggregate particles in asphalt mixes. However, this method is subjective, making it less reliable to accurate measurements. The objective of this study was to investigate three flat and elongated particles ratios (FERs); 2:1, 3:1 and 5:1 using a modern 3-D laser scanning technique and compare results with ASTM D 4791. Based on the ASTM D4791, the Superpave specification allows for a maximum of 10% coarse aggregates to have FER of 5:1 in asphalt mixes. Eight crushed stones used for road construction in South Africa were investigated. The results indicate that three crushed stones would be rejected by the Superpave specification whereas all eight crushed stones could meet the specification based on the results from the 3-D laser scanning method.
Laboratory investigation on using coal ash as selected formation layer in a railway track substructure
(South African Institution of Civil Engineering, 2019-10) Mokoena, Refiloe; Mvelase, Gculisile M
The study presented in this paper aims to promote the use of coal ash in railway infrastructure as a more economical and sustainable material. The study serves as a preliminary investigation on using coal ash as one of the structural layers within the railway track substructure during formation rehabilitations in close proximities to coal power stations. A laboratory investigation was carried out to characterise and assess the suitability of ash in a typical railway track formation. The ash was sourced from two power stations in Mpumalanga, South Africa. The samples were evaluated against Transnet specifications for railway earthworks, the coarse ash met all specifications while the grading of the fine ash limited its suitability for use as one of the formation layers. Additional tests were performed according to national specifications for road works as no such testing is required for railway material. The tests were done to quantify any potential deleterious nature of the ash, which include pH and electrical conductivity. The soluble salt content and pH was found to be within acceptable limits. Two blends of bottom ash containing 25% and 50% fly ash from Kriel power station were tested in an attempt to reduce the OMC. Results showed a reduction in OMC and increase in MDD and CBR as the fly ash content increased.
Material Characterisation and Design of Alternative Pavement Surfacing for Steep Hilly Sections of Low-Volume Roads in Ghana
(2024-01) Anochie-Boateng, J; Debrah, EK; Mvelase, Gculisile M; Agyekum, P; Asenso-Gyambibi, D
Identifying appropriate pavement design options for higher-risk sections of low-volume roads is a crucial 3 part of Ghana’s strategy to improve sustainable all-season rural access. This paper investigates the 4 suitability of alternative surfacing for steep hilly sections of low-volume roads in Ghana with gradients 5 above 12%. Typically, these roads are constructed with weak natural gravel as the wearing course. To 6 address the persistent drainage and erosion problems on these steep sections, four alternative rigid 7 pavement options were designed and proposed. These were interlocking concrete block paving (ICBP), 8 roller compacted concrete (RCC), thin mesh reinforced concrete (TMRC), and non-reinforced concrete 9 (NRC). We present the material selection, pavement designs, and life-cycle economic analysis of these 10 four cost-effective pavement options. The present worth of cost life-cycle cost appraisal of the options 11 considering the initial cost, probable maintenance cost, and salvage value of the road asset over a 25-year 12 service life, with a pavement design life of 15 years and an analysis period of 25 years are discussed. The 13 results indicate that all four alternative surfacing types are economically feasible and comparable, 14 although RCC has the lowest cost, while the ICBP option is relatively the most expensive.
Sustainable pavement construction: Use of non-potable water and smart techniques for compaction
(Alive2Green, 2021-12) Rampersad, Ashiel; Mvelase, Gculisile M; De Jager, Peta
The western cape government reported an annual mean near-surface (2m) temperature (°C) change from the median and the 10% and 90% percentiles projected for 2036 – 2065 and 2066 – 2095. Across most of the country, model-simulated rainfall is slightly lower than observed, although the east-west gradient in rainfall is adequately represented. Autumn, which is the transition period between summer and winter, denotes slightly higher rainfall in the observed east and Western Cape region. Winter rainfall is higher in the Cape Town region in the observations, compared to the model simulations. The temperature and rainfall variations have a direct impact on the restriction of available potable water required. Due to the limited peer-reviewed research and use of non-potable water in road construction, this chapter will investigate preliminary laboratory research into the area as well as smart compaction techniques.
Three-dimensional laser scanning technique to quantify aggregate and ballast shape properties
(Elsevier, 2013-06) Anochie-Boateng, Joseph; Komba, Julius J; Mvelase, Gculisile M
There is a need to improve the measurements of shape characteristics of aggregates and ballast materials used in the construction of road, airfield, and railway track infrastructures. The fundamental shape properties of aggregate and ballast, including form (roundness, flatness, elongation, sphericity), angularity, and surface texture (roughness) have not been accurately quantified because of their irregular and non-ideal shapes. Current developments are shifting from manual and subjective methods towards a more accurate and automated techniques to quantify aggregate shape properties. This paper validates a new flakiness index equation using three-dimensional (3-D) laser scanning data of aggregate and ballast materials obtained from different sources (quarries) in South Africa. The new equation uses volume ratio instead of the traditional mass ratio to determine flakiness index of aggregates and ballast materials. It is concluded that the validated equation can be used with confidence to determine flakiness index of aggregate and ballast materials.
The use of laser technology to investigate the effect of railway ballast roundness on shear strength
(Elsevier, 2017-06) Mvelase, Gculisile M; Gräbe, PJ; Anochie-Boateng, Joseph
The heavy haul coal line of the South African railway network is facing a problem where ballast particles are becoming rounded, negatively affecting performance and thus leading to shorter planned maintenance cycles. This has been attributed to the lack of a more scientific way of evaluating the ballast shape properties. The objective of this paper is to investigate the effect of ballast particle roundness on shear strength properties of five ballast materials used on the Transnet Freight Rail heavy haul coal line. A river pebble sample was included in the study as the reference material for extremely rounded ballast. All six materials were scanned in a 3-D laser scanning system to develop models of the ballast and the river pebble particles. Based on the laser scanner results, a new empirical model has been developed to determine the surface area of ballast materials. The surface area values were further used to develop a chart to assess different particle shapes with varying degrees of roundness. Triaxial tests were conducted to determine the effect of the roundness on the shear strength properties of the materials. A Mohr-Coulomb failure model was successfully developed from the results to represent individual materials tested. The overall results show that the angle of internal friction increases with roundness of the sample greater than 0.8. More rounded particles have values between 0.6 and 0.7, whereas less rounded particles have values between 0.8 and 1.3. The outcomes of this study would assist with quality assessments in the field and whether or not a degraded ballast track layer has to be replaced.
Use of non-potable water in pavement construction: A laboratory study using seawater
(2021-06) Rampersad, Ashiel; Mvelase, Gculisile M
The Intergovernmental Panel on Climate Change (2018) projects that global warming is likely to reach 1.5°C above pre-industrial levels between 2030 and 2052. The effect of climate change on warmer temperatures and longer lasting drought periods has been well documented in Southern Africa. The Global Disaster Alert and Coordination System (2020) has declared an orange level (intermediate impact) drought for 6 months in South Africa and Lesotho making them water scarce countries. Construction processes rely on the use of potable water. In road construction, the moisture content is an important factor that affects the density of a road material. Due to the limited research in South Africa on use of non-potable water in road construction, there has been a greater need to conduct laboratory research. This paper highlights research through laboratory testing of granular sub-base material mixed with seawater obtained from the Indian Ocean. Aggregate originating from dolerite, tillite and sandstone rock quarries were used. Potable tap water was used as a baseline to the tests. Promising results are showed in the laboratory testing and it is advisable that further research is required going forward.

Browsing by Author "Mvelase, Gculisile M"

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