Research Publications/Outputs

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Browsing Research Publications/Outputs by browse.metadata.impactarea "Advanced Materials Testing"

Now showing 1 - 3 of 3
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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.
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    Investigating the use of isothermal calorimetry for predicting physical properties of cements
    (2021-09) Mokoena, Refiloe; Motau, T; Mturi, George AJ
    Isothermal calorimetry is a useful technique for studying the cement hydration process that measures the heat flow of cement paste during hydration. Standard cement properties, such as compressive strength, setting times and compatibility can be derived from calorimetry investigation. This becomes relevant in assisting with monitoring the strength development during construction activities and studying the thermal related behaviour of concrete structures. During this study, the heat generated from the cement hydration reactions was investigated of four different cement types, namely CEM II/B-V 32.5N, CEM II/B-V 42.5N, CEM II/A-M (S-V) 42.5R and CEM I 52.5N. Correlations between the calorimeter results and the (i) initial setting time and final setting time; (ii) 28 day compressive strength and; (iii) fineness, were established for the cement types investigated. With the exception of early-day strength, the results indicated strong correlations between the investigated parameters and the cement hydration curves. This was particularly the case for the setting time of the cements with an R2 value of 0.82 and 0.89 for the initial and final setting times respectively.
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    The use of plastic waste in road construction
    (Alive2green, 2021-12) Mturi, George AJ; O’Connell, Johan S; Akhalwaya, Imraan; Ojijo, Vincent O; Mofokeng, Tladi G; Ncolosi, Nonzwakazi; Smit, Michelle A; De Jager, Peta
    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.