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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

Internationally acclaimed academic applauded on Africa Day
2011-06-02

 
 Prof. Ali Mazrui, an internationally acclaimed and renowned academic.

One of the world’s top academics was given a warm welcome in the rather cold Free State recently.

Prof. Ali Mazrui, an internationally acclaimed and renowned academic, visited us as part of our Africa Day celebrations as arranged by the Centre for Africa Studies. He delivered a keynote address, entitled ‘Pro-democracy uprisings in an African experience: from Sharpeville to Benghazi.’

A festive atmosphere and the sound of drums welcomed this intellectual giant as well as other delegates upon their arrival at the CR Swart Auditorium on our Bloemfontein Campus. Some of the delegates who attended the Africa Day Celebrations, included: Mr Tom Amolo, High Commissioner from the Republic of Kenya; Mr Dan Kgothule, MEC of Arts and Culture in the province; Prof. Jeff and Dr Carla Ramsdell, visitors from America; Dr Allan Boesak and Prof. Nicky Morgan, Vice-Rector: Operations.

Prof. Frederick Fourie, former Vice-Chancellor and Rector of our university, also attended the celebrations, as did some scholars from neighboring schools.

Welcoming Prof. Mazrui, Prof. Jonathan Jansen, Vice-Chancellor and Rector of our university, quipped that he was relieved the world had not ended the previous weekend as was predicted, because he was looking forward to listening to such a renowned intellectual.

Prof. Lucius Botes, Dean of Humanities, followed Prof. Jansen at the podium. He said the ability to go from following a bridging course to being one of the top 100 intellectuals in the world, indeed distinguishes Prof. Mazrui as an exceptional academic. This intellectual is, among others, an Albert Luthuli Professor at the University of Jos, Nigeria and Andrew D. Professor Emeritus and Senior Scholar in Africana Studies at Cornell University.

In his introduction, Prof. Mazrui said he feels honored and flattered by this opportunity. He proceeded by referring to the history of Africa Day and added that he would rather prefer an Africa Week to an Africa Day to ensure that everybody has the opportunity to celebrate the continent.

He sang the praises of South Africa, as almost every other African country which attained liberation from European colonial rule in the 20th century, has been unable to maintain its democratic order beyond its first decade of independence.

“The Republic of South Africa, on the other hand, liberated Nelson Mandela in 1990, held its first democratic election in 1994, and already has its third president. Nearly two decades after Apartheid, South Africa has not outlawed opposition parties, or experienced a military coup, or permitted the Head of State to govern the country as a dictator.”

In his speech he compared the uprisings in Sharpeville during 1960 and Soweto during 1976 with the more recent pro-democracy uprisings in North Africa, based on the role that weapons and the lack thereof, as well as the youth and women played in the respective cases.

He concluded by saying the uprisings in Tunisia and Egypt have already resulted in ousting dictators who had been entrenched in power for decades, adding that in Libya a third dictator’s future is on the line. “Never in the history of the Arabs have there been so many popular uprisings which seem to be inspired neither by Islam nor by anti-imperialism, but in the quest for liberal reforms. Half a century earlier in Sharpeville and Soweto, South Africans experienced their own political awakening.”

Prof. Kwandiwe Kondlo, Director of the Centre for Africa Studies, closed the event with a word of thanks to the American academic and his wife, guests and attendees. He said discussions prior to the event revealed that more research has to be done regarding gender issues on the continent.

Prof. Mazrui also participated in conversations at the institute and a media briefing which was hosted earlier the day.

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