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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

SA cannot sustain momentum - Boesak
2010-09-02

Photo: Stephen Collett

South Africa finds it increasingly difficult to live up to the challenges facing it as a nation because of its failure to meet its democratic ideals and possibilities, peace and lack of self-belief.

This was according to renowned cleric and former political activist, Dr Allan Boesak, who recently delivered the CR Swart Memorial Lecture, the oldest memorial lecture at the University of the Free State (UFS). His lecture was on the topic Creating moments, sustaining momentum.

He said South Africa had plenty of opportunities to show the whole world what was possible if all the people of this country joined hands and worked together to build a truly united society. However, he said, the country somehow invariably contrived to find its way out of these wonderful possibilities.

He cited events of historical significance like Codesa, the inauguration of Nelson Mandela as the first democratic president of South Africa, the assassination of South African Communist Party leader, Chris Hani; and the rugby and soccer world cups.
To drive his point home about this dismal failure of the country to “sustain momentum”, he alluded to the current public servants’ strike that is gradually crippling public service.

“The public servants’ strike was neither unexpected nor is it completely unjustifiable. Most of us have understanding for the frustration of teachers and health workers. Their demands resonate with most of us, and I think that it is scandalous of SACP fat cats to tell workers to “stop crying like babies,” he said.

He also added to the criticism of the much-maligned decision of the government to spend billions of taxpayers’ money to purchase weapons when there was “no discernible military threat” to the country. He said the greatest threat to the security of the country was poverty, inequality and social cohesion.

“As for the argument that arms sales bring in foreign exchange – how can we be instrumental in killing the poor elsewhere with the intention of feeding our poor, and then our ill-gained profits feed only the already well-fed?” he asked.
“Can we see the hopeless contradiction, the total impossibility of being both the apostle of peace and a merchant of death?”

He also lambasted the Black Economic Empowerment (BEE) policy of the government which he said benefited only those connected to the political aristocracy.

“It couples with the unashamed, in-your-face display of wealth by the privileged elite in this country, the crass materialism of the so-called “bling generation”, and the casual carelessness with which promises to the poor are given and treated. It is only the public symptom of the deep-seated scorn our political elites feel for the poor,” he said.

He said the government’s disdain to the poor was “setting fire to our future”.

“The anger of people on the ground can no longer be denied or ignored, and little by little, the leadership articulating and directing this anger is being estranged from politically elected leadership, and even more disturbing, from our democratic processes,” he said.

He concluded that the country’s difficulty in dealing with race and racism was putting the reconciliation process kick-started by Mandela just over a decade ago, under a threat.
 

 

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