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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

Nat Nakasa the inspiration behind UFS academic’s PhD thesis
2017-01-09

 Description: 001 Dr Willemien Marais Tags: 001 Dr Willemien Marais

Photo: Supplied

“I’m interested in alternative ways of approaching things, so I wanted to look at how journalism can be used in an unconventional way to contribute to a developing society.”

This is why Dr Willemien Marais, a lecturer in the Department of Communication Science at the University of the Free State (UFS), decided to title her thesis: Nat Nakasa as existential journalist, describing a form of journalism that places emphasis on the individual’s experiences.

“Existentialism is a philosophy that provides scope for an individual approach to life, and I like Nat Nakasa’s writing because of his excellent sense of humour despite his horrific circumstances as a black journalist during apartheid,” she says.

A practical approach to writing

Dr Marais analysed Nat Nakasa’s approach to journalism through articles he wrote in the early 1960s. She searched for relevant themes of existentialist philosophy in Nakasa’s work in order to prove that he could be read as an existential journalist.

She mentions that in terms of contemporary relevance, Nakasa’s approach to journalism suggests that existentialism could provide the journalist with a practical approach to writing, especially for those journalists working in developing societies.

“The relevance of this approach lies in the fact that any society is always between things – the old and the new – which might require the journalist to operate outside the boundaries of conventional journalism.”

This study was qualitative in nature because of the interpretation required. She mentions that it was basically one of many possible interpretations of Nakasa’s work; with this one using existentialism as a lens.

An intellectually stimulating thesis

Dr Marais quotes French existentialist Jean-Paul Sartre, who said that interpreting someone’s work, especially someone who was no longer alive, was open to “thousands of shimmering, iridescent, relevant meanings”, and her research represents one of these possible meanings of Nakasa’s work as a journalist.

When asked how long she had worked on her thesis, Dr Marais simply answered “too long!” She mentions that her thesis was initially more of an intellectual exercise. Whereas the actual act of writing took about four months, she spent many years thinking about the topic. “Now that all is said and done, I realise I had to grow into the topic. It took me a while to realise that true understanding does not come overnight!”

Dr Marais mentions that other than herself and the work of Nat Nakasa, there were no other roleplayers involved. “For many, many years it was just Nat Nakasa and I. It was frustrating and exhilarating all at the same time.”

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