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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

DF Malherbe Memorial Lecture
2005-05-19

DF Malherbe Memorial Lecture: Language and language activism in a time of transformation (summary)
Proff Hennie van Coller and Jaap Steyn

Language activism necessary for multilingualism
The awareness is growing that language activism will be needed to bring about a truly democratic multi-lingual society. What is quite clear is that a firm resolve must continuously resist the concentrated pressure on Afrikaans-medium schools (and universities) to allow themselves to be anglicised through becoming first parallel medium, then dual medium, and finally English medium institutions.

Proff Hennie van Coller and Jaap Steyn said this last night (Wednesday night) in the 24th DF Malherbe Memorial Lecture at the University of the Free State. Prof van Coller is head of the Department Afrikaans, Dutch, German and French at the UFS. Both are widely honoured for their contributions to Afrikaans and the promotion of Afrikaans.

They discussed three periods of transformation since 1902, and said about the current phase, which started in 1994:  “Besides all institutions and councils having to be representative of South Africa’s racial composition, places of education were required to open their doors. Quite rapidly this policy has had the result that schools and universities may be solely English medium, but not solely Afrikaans medium. Afrikaans medium institutions — if they claim the right to remain Afrikaans — are quickly branded racist, even though their student body may include all races.

“Education departments are presently exerting great pressure on Afrikaans medium schools to become double or parallel medium schools.  Parallel medium education is an equitable solution provided it can be sustained. Established parallel medium schools, such as Grey College in Bloemfontein, have catered even-handedly for English and Afrikaans speakers for decades. But the situation is different in the parallel medium (and still worse in the double medium) schools that spring up usually at the behest of a department of education.

“Afrikaans schools are converted almost over-night into parallel or dual medium schools without any additional personnel being provided. Depending on the social environment, a parallel medium school becomes reconstituted as a dual medium school on average in five to eight years, and dual medium school becomes an English-only school in two to three years. Some Afrikaans medium schools have become English medium in just three years.

“Though the Constitution recognises mono-lingual schools, officials in the provinces insist that Afrikaans schools become dual or parallel medium; English medium schools are left undisturbed. One must conclude that the tacit aim of the state is English as the sole official language, despite the lip-service paid to multi-lingualism, and the optimistic references to post-apartheid South Africa as a ‘rainbow’ nation.”

They said a recent study has shown that the 1 396 Afrikaans schools in the six provinces in 1993 have dwindled to 844. The fall off in the Free State is from 153 to 97; in the Western Cape from 759 to 564; in Gauteng from 274 to 155; in Mapumalanga from 90 to 3; in the North West from 82 to 13; and in Limpopo Province from 38 to 12.

They said the changes at universities, too, have been severe, as university staffs well know. Ten years ago there were five Afrikaans universities. Today there are none. The government demanded that all universities be open to all, which has meant that all universities have had to become English medium. And no additional funding was forthcoming for the changes. The government policy amounts to a language “tax” imposed on the Afrikaans community for using Afrikaans.

“Only when all schools (and universities) are English will the clamor cease. Academics and educationists are beginning to speak openly of forming pressure groups to save Afrikaans schools, and of using litigation as one of their methods. 59% of Afrikaans parents have said they would support strong action if Afrikaans were no longer a medium of instruction at schools.”

 

 


 

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