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29 November 2022 | Story Leonie Bolleurs | Photo Leonie Bolleurs
UFS green concrete
The Department of Engineering Sciences (EnSci) welcomes collaborations with other departments at the UFS. Pictured here are, from the left: Louis Lagrange, Head of EnSci, Prof Kahilu Kajimo-Shakantu, Head of the Department of Quantity Surveying and Construction Management, Dr Abdolhossein Naghizadeh, and Megan Welman-Purchase, analytical scientist in the Department of Geology.

More than 30 million tonnes of fly ash (residue from coal combustion in power plants) are generated in South Africa annually, with 96% of that being disposed of in landfills. There is thus more than enough of this key ingredient to produce green concrete. 

Green concrete, so called due to its environmentally friendly benefits, is an eco-friendly alternative to conventional concrete based on the Portland cement binder. During the production of green concrete, less carbon dioxide is released into the atmosphere than with the production of ordinary Portland cement (OPC). The latter accounts for up to 8% of all global carbon emissions.

Successful tests

In the Green Concrete Lab, established in 2021 within the Department of Engineering Sciences (EnSci) on the Bloemfontein Campus of the University of the Free State (UFS), Dr Abdolhossein Naghizadeh, Senior Lecturer, researcher, and engineer, is working on green cement and concrete projects.

He uses ‘geopolymer’ technology and a mix of waste materials, alkaline solutions, and recycled aggregates to form concrete mixtures that can provide properties similar to conventional concrete.

Besides being a synthesised inorganic material (not a petrochemical product), the geopolymer cement he introduced has the following properties: it is made from a reaction between aluminosilicate materials and strong alkalis (5-7% of the concrete mixture), it uses water and by-products as raw materials, it does not calcinate lime, thus giving it a low carbon emission, and it is also beneficial from a waste management point of view. 

The waste materials used can include waste from industrial and agricultural sources, such as fly ash, rice husk ash, sugar-cane bagasse, or corncob ash, as well as natural materials such as volcanic ash. In South Africa, sufficient amounts of industrial and agricultural waste are available. 

“So far, we have successfully tested various types of green concrete based on different waste materials,” says Dr Naghizadeh. 

Besides researching the green mixture proportions in the lab, Dr Naghizadeh and his students focused their attention on establishing the strength, durability, workability, and production cost of the product. 

They compared green concrete with conventional concrete. Green concrete’s workability is slightly lower (but he believes that with appropriate mix design it can be corrected), and it has a much higher compressive strength (50-90 MPa), a smaller carbon footprint, and comparable production costs to conventional concrete (depending on the mix design). A very high level of resistance against alkali-silica reaction (concrete cancer) is also present, as well as resistance to carbonation, sulphate attack, and acid attack.
So far, we have successfully tested various types of green concrete based on different waste materials.– Dr Naghizadeh. 

He explains, “The superior durability performance of green concrete is related to its chemical compositions and microstructure. For example, the lack of calcium content in the composition provides better resistance to alkali-silica reaction. At the same time, stronger bonds between elements and polymeric microstructure provide better resistance against acids and fire.”

With all the work and research of the past year and a half, Dr Naghizadeh says they are at the stage where they can prescribe green concrete production recipes for the industry parties based on the specified application and the materials they have.

Biggest accomplishments

“We transferred most of the experimental works to the Green Concrete Lab at the beginning of 2022, which improved our productivity tremendously. Since then, nine journal papers and three peer-reviewed conference papers have been published as outputs of the research projects. Currently, there are also multiple publications under review or in the development stages,” says Dr Naghizadeh.

In addition to him, there are three master's students and one research associate working on their own individual projects.

The department is very proud of its research outputs. Dr Naghizadeh was either author or co-author of all 12 research papers. The focus of these papers was mostly on the formulation of green concrete, based on locally available agricultural waste materials, the formulation of one-part geopolymer cement (when aluminosilicate raw material is replaced with pre-activated aluminosilicate material, water can be used instead of alkali solution), and the development of ambient-cured green concrete (replacing the aluminosilicate raw material with a blend of materials).

Dr Naghizadeh is also the project leader of a group of scientists from local and international universities who are researching sustainable construction materials. These institutions include the Universities of Johannesburg, KwaZulu-Natal, Yaoundé in Cameroon, Erzurum Technical University in Turkey, as well as Nelson Mandela University and the Central University of Technology, which recently came on board. 

 


 


News Archive

Teachers should deal with diversity in education - Prof. Francis
2010-10-08

At the occasion were, from the left: Prof. Jonathan Jansen, Rector and Vice-Chancellor of the University of the Free State (UFS); Prof. Francis; and Prof. Driekie Hay, Vice-Rector: Teaching and Learning at the UFS.
Photo: Jaco van der Merwe

Prof. Dennis Francis, the Dean of the Faculty of Education at the University of the Free State (UFS), recently delivered his inaugural lecture on Troubling Diversity in South African Education on the Main Campus in Bloemfontein.

He urged teachers to be open to what “diversity” might mean in a particular context and how diversity relates to either inclusion or exclusion.

“An approach that promotes the inclusion of all must be based on an understanding of how exclusion operates in ways that may have typical patterns of oppression, but differ in the specific ways that exclusion is expressed and becomes normalised in that context,” he said.

“The good teacher thus seeks to understand how these forms of exclusion may develop in the school’s context and respond through taking thoughtful action to challenge them. It may require creating a climate that enables the silent to speak and recognising that not all groups communicate in exactly the same ways.”

He said teachers also had to affirm the experiential base of learners and students. He said there was an assumption that students would be more effective practitioners if their own experience were validated and explored.

“It is crucial that the students’ own history is treated as valuable and is a critical part of the data that are reflected,” he said. “Equally important is that such stories and similar activities are intentionally processed to enable students to make the connections between personal experience and relevant theory.”

He also urged them to challenge the ways in which knowledge had been framed through oppression.

“Schools are often characterised by messages that draw on one or another form of oppression. Thus, expectations are subtly or in some cases unsubtly communicated, e.g. that girls are not good at physics, or that, while white learners are strong in abstract thought, African learners have untapped creativity, and so on,” he continued.

“For someone to integrate into their role as educators a commitment against oppression means confronting obstacles that one may previously have shied away from, such as challenging authority, naming privilege, emphasising the power relations that exist between social groups, listening to people one has previously ignored, and risking being seen as deviant, troublesome or unpopular.”

Furthermore, Prof. Francis said dealing with diversity in education was always affectively loaded for both students and teachers. He said in South Africa one injunction from educators was to be “sensitive” and thus avoid risking engagement with the contentious issues around imbalances of power.

“If both students and teachers are to confront issues of oppression and power in any meaningful way, we need to design more purposely for the difficulties they will encounter, for example, creating a classroom environment that promotes safety and trust so that all students are able to confront and deal with prejudice and discrimination. Classroom environments will need to balance the affective and cognitive in addressing issues of diversity and social justice,” he added.

He also said that teachers should recognise the need to complement changing attitudes with attempts to change the structural aspects of oppressions.

“To prevent superficial commitments to change, it is important for students to explore barriers that prevent them from confronting oppressive attitudes and behaviours. In this way students are able to learn and see the structural aspects of oppression,” he said.

“Equally important, however, is to get students to examine the benefits associated with challenging oppression. A fair amount of time must therefore be spent on developing strategies with students which they will be able to use practically in challenging oppression.”

He also advised educators to affirm the capacity of staff and learners to act and learn in ways that do not replicate patterns of oppression.

“Many South African schools have survived both the harsh repression of apartheid and the continuing legacy of oppression of various kinds. Despite that, we are often as educators made aware of the ways in which young people in particular affirm themselves and each other in creative and confident ways,” he concluded.

Media Release
Issued by: Lacea Loader
Director: Strategic Communication (acg)
Tel: 051 401 2584
Cell: 083 645 2454
E-mail: loaderl@ufs.ac.za  
7 October 2010
 

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