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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

Historians must place African history on world stage – Dr Zeleza
2017-05-30

 Description: Historians must place African history on world stage Tags: Historians must place African history on world stage

From the left: Panellists Rev Henry Jackson,
Prof Irikidzayi Manase and Arno Van Niekerk at a book
launch and panel discussion on Africa Day hosted by the
UFS Sasol Library.
Photo: Mamosa Makaya

“African historians must take seriously the challenge of placing African history in world history, and in the history of our species, Homo sapiens.”

With these words, Dr Paul Tiyambe Zeleza, Vice Chancellor of the United States International University-Africa in Nairobi, Kenya, stressed the continent’s challenge.

According to him the contest should continue to recover and reconstruct Africa’s long history. Liberating African knowledges can be done by: “Provincialising Europe that has monopolised universality, universalising Africa beyond its Eurocentric provincialisation, and engaging histories of other continents on their own terms.”

University celebrates Africa Month in various ways  
Dr Zeleza delivered the ninth Africa Day Memorial Lecture, titled The Decolonisation of African Knowledges, at the University of the Free State (UFS). The lecture, hosted by the Centre for Africa Studies (CAS), took place on 24 May 2017 in the Equitas Auditorium on the Bloemfontein Campus and was one of the ways in which the UFS celebrated Africa Month.

Scholars should immerse themselves in these thoughts

Dr Zeleza focused on two issues, which he said were interconnected. They were the unfinished project of decolonising African knowledges and the continent's positioning in global knowledge production.

He said Africa’s scholars and students should “immerse themselves in the rich traditions of African social thought going back millennia”. According to him the continent’s research profile still remains weak in global terms.

“It is imperative that the various key stakeholders in African higher education from governments to the general public to parents, and to students, faculty, staff, and administrators in the academic institutions themselves, raise the value proposition of African higher education for 21st century African societies, economies, and polities.”

“Colonialism is associated with injustice
and inequality, but what happens when
our liberators become our oppressors?”

Library celebrates with panel discussion and book launch
The UFS Sasol Library celebrated Africa Day by presenting a book launch and panel discussion on 25 May 2017, on the pertinent and current political theme of land redistribution with a comparative basis of land invasions in Zimbabwe.

Prof Irikidzayi Manase discussed his book White Narratives: The Depiction of Post-2000 Land Invasions in Zimbabwe, accompanied by Rev Henry Jackson who wrote Another Farm in Africa. A perspective of the economic implications of land redistribution in South Africa was discussed by panellist Arno Van Niekerk: Senior Lecturer of Economics at the UFS Faculty of Economic and Management Sciences.

Inequality still an African problem
The content of the books are a stark reminder of the burning issues of inequality and loss of identity of those who lost their farms in Zimbabwe, a collection of memoirs by white farmers and their families. Rev Jackson gave a religious perspective on reconciliation, forgiveness and the question of land ownership, saying that healing of injustice begins with forgiveness of past transgressions.

Van Niekerk highlighted that while land issues were important, “social cohesion is affected by the economic decisions that will be made”. In closing, Prof Manase called for serious consideration of what the future may hold. “Colonialism is associated with injustice and inequality, but what happens when our liberators become our oppressors?” 

The panel discussion was attended by staff and students of the university, and was lit up by robust discussions on possible historical and future solutions to the question of land, decolonisation and political power struggles in Southern Africa and lessons to be learned from Zimbabwe.

UFS celebrates Africa Month (24 May 2017)

 

 

 

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