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Strength, durability, thermal performance and sustainability assessment of one-part geopolymer concrete masonry units.
(Stellenbosch : Stellenbosch University, 2024-12) Bhayat, Moegamat Tashriq; Babafemi, Adewumi John; De Villiers, Wibke; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ANGLISH ABSTRACT: South Africa currently faces a major backlog in the delivery of affordable housing units, which are typically constructed with conventional fired clay-based or cement-based masonry units. Additionally, the production of clay-based and cement-based masonry places a significant impact on the natural environment due to the clay firing and limestone calcination procedures, respectively. The need for alternative masonry units (AMUs) satisfying social, economic and environmental performance is evident. One-part geopolymer cement, produced from the alkali activation of aluminosilicate waste via solid alkali activators, has become an attractive low-carbon cement alternative showcasing superior mechanical, durability and thermal properties. Additionally, the use of alternative concrete aggregates is valuable toward mitigating the intense pressure placed on conventional aggregate resources by the built environment. This study investigated fly ash (FA), ground granulated blast furnace slag (GGBFS) and metakaolin (MK)-based one-part geopolymer concrete-based AMUs synthesised by solid alkali activators comprising sodium hydroxide (NaOH), sodium metasilicate pentahydrate (Na₂SiO₃.5H₂O) and calcium hydroxide (Ca(OH)₂). Additionally, expanded vermiculite (EV) and recycled plastic waste (RESIN8) were substituted as an alternative fine aggregate. The AMUs developed in this study include the FA and GGBFS-based (FABS) and the FA and MK-based (FAMK) units. EV was incorporated at 15% replacement in the development of the EV-based FA and GGBFS (FSEV) unit and the EV-based FA and MK (FMEV) unit. RESIN8 was incorporated at 5% replacement in the development of the RESIN8-based FA and GGBFS (FSR8) unit. All AMUs were subject to ambient curing. The AMUs were tested for their mechanical properties (compressive strength and elastic modulus) and density, durability properties (cold and boiled water absorption, initial rate of absorption, shrinkage and efflorescence extent), thermal properties (thermal conductivity, thermal resistance and thermal transmittance of wall specimens) and sustainability (cost analysis and lifecycle assessment). The average compressive strength of all AMUs satisfies the minimum strength requirement for masonry units. The elastic modulus for all AMUs falls within an acceptable range for masonry materials. The water absorption for all AMUs falls under the absorption limit for concrete-based masonry units. The initial rate of absorption for all AMUs are within an acceptable range for masonry units. All AMUs exhibit higher shrinkage in comparison to conventional concrete. The extent of efflorescence for all AMUs was slight to none. The thermal resistance (R-value) for all AMU wall specimens does not meet the minimum requirement for external walls in South Africa, yet the walls still possess comparable R-values to that of conventional concrete-based masonry units used in South Africa. The cost of the AMUs is roughly two times higher than that of a conventional concrete-based masonry unit, highlighting the economic challenge of adopting one-part geopolymer concrete as an alternative to conventional masonry materials for affordable housing construction. A cradle to gate and cradle to grave life cycle analysis of all AMUs showcased a reduction between 30% to 90% in the carbon footprint when compared to conventional masonry units. Overall, the outcomes of this study showcase the potential of one-part geopolymer cement and alternative aggregates to replace conventional masonry materials.
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Creative agency in the colonial encounter: foundations for a decolonial pedagogy
(Taylor & Francis, 2024-12-10) Fataar, A.
This essay emphasises the imperative to move from discussions about decolonising education to the practical implementation of a decolonial pedagogy. This task necessitates challenging Eurocentric perspectives and incorporating diverse insights into curriculum design and pedagogical processes. By drawing on Edward Said’s concepts of democratic humanism, worldliness, and contrapuntal, the essay argues for an expanded understanding of colonial and postcolonial contexts that highlight the agency of colonised peoples. It underscores the significance of acknowledging cultural connections and interactions as vital components of human formation. The essay explores how enslaved people at the Cape of Good Hope navigated their circumstances, establishing creative agency to shape their worlds. Briefly discussing the literacy practices of enslaved people and the literary portrayals of enslaved women, the essay illustrates how a decolonial pedagogy can offer a more inclusive and critical perspective on historical cultural formations.
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Consumers' motivations to engage with local brands on social media
(Stellenbosch University, 2024-12) Esterhuyzen, Lisa
The 'consumer brand engagement' (CBE) concept comprehensively reflects consumers' motives for social media use, particularly digital consumer engagement behaviour. However, despite the growing scholarly interest in addressing 'engagement', disagreement exists regarding the nature of engagement behaviours and the predictive role of consumer motivations. Further, although there is a ‘buy local’ movement whereby consumers are encouraged to support local brands, the role of ethnocentrism in consumers’ decision to engage with local brands on social media has not been examined. To address these gaps in the literature, this study drew from the Uses and Gratifications Theory to examine CBE on social media in a local South African wine brand context and the possible moderating effects of ethnocentrism.
A sequential mixed-method research design comprised of a qualitative phase one (focus group discussions) and a quantitative phase two (survey questionnaire) was utilised. The data recorded from phase one was thematically analysed, whereas Partial Least Squares Structural Equation Modelling (PLS-SEM) was employed during phase two. Findings from phase one suggested that the concept of ‘local brand’ is contextual and that although consumers hold positive sentiments towards phrases such as ‘local is lekker’, an overall negative perception of South African product quality persists. Results from phase two revealed that consumer motivations to engage on social media predict consumer online brand-related activities (COBRAs) in varying degrees and that consumer ethnocentrism plays a limited moderating role.
Theoretically, this study contributes by refining the model proposed by Buzeta et al. (2020), thus providing insight into the interrelationships that exist between consumers’ motives to engage with local wine brands on social media and their subsequent COBRAs. Managerially, brand managers need to understand that different motivations are associated with different COBRAs and adjust their social media campaigns accordingly.
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Mimicking DSpace deposit
(2024-11-18) W. Klapwijk