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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

“To forgive is not an obligation. It’s a choice.” – Prof Minow during Reconciliation Lecture
2014-03-05

“To forgive is not an obligation. It’s a choice.” – Prof Minow during the Third Annual Reconciliation Lecture entitled Forgiveness, Law and Justice.
Photo: Johan Roux

No one could have anticipated the atmosphere in which Prof Martha Minow would visit the Bloemfontein Campus. And no one could have predicted how apt the timing of her message would be. As this formidable Dean of Harvard University’s Law School stepped behind the podium, a latent tension edged through the crowded audience.

“The issue of getting along after conflict is urgent.”

With these few words, Prof Minow exposed the essence of not only her lecture, but also the central concern of the entire university community.

As an expert on issues surrounding racial justice, Prof Minow has worked across the globe in post-conflict societies. How can we prevent atrocities from happening? she asked. Her answer was an honest, “I don’t know.” What she is certain of, on the other hand, is that the usual practice of either silence or retribution does not work. “I think that silence produces rage – understandably – and retribution produces the cycle of violence. Rather than ignoring what happens, rather than retribution, it would be good to reach for something more.” This is where reconciliation comes in.

Prof Minow put forward the idea that forgiveness should accompany reconciliation efforts. She defined forgiveness as a conscious, deliberate decision to forego rightful grounds of resentment towards those who have committed a wrong. “To forgive then, in this definition, is not an obligation. It’s a choice. And it’s held by the one who was harmed,” she explained.

Letting go of resentment cannot be forced – not even by the law. What the law can do, though, is either to encourage or discourage forgiveness. Prof Minow showed how the law can construct adversarial processes that render forgiveness less likely, when indeed its intention was the opposite. “Or, law can give people chances to meet together in spaces where they may apologise and they may forgive,” she continued. This point introduced some surprising revelations about our Truth and Reconciliation Commission (TRC).

Indeed, studies do report ambivalence, disappointment and mixed views about the TRC. Whatever our views are on its success, Prof Minow reported that people across the world wonder how South African did it. “It may not work entirely inside the country; outside the country it’s had a huge effect. It’s a touchstone for transitional justice.”

The TRC “seems to have coincided with, and maybe contributed to, the relatively peaceful political transition to democracy that is, frankly, an absolute miracle.” What came as a surprise to many is this: the fact that the TRC has affected transitional justice efforts in forty jurisdictions, including Rwanda, Sierra Leone, Cambodia and Liberia. It has even inspired the creation of a TRC in Greensborough, North Carolina, in the United States.

There are no blueprints for solving conflict, though. “But the possibility of something other than criminal trials, something other than war, something other than silence – that’s why the TRC, I think, has been such an exemplar to the world,” she commended.

Court decision cannot rebuild a society, though. Only individuals can forgive. Only individuals can start with purposeful, daily decisions to forgive and forge a common future. Forgiveness is rather like kindness, she suggested. It’s a resource without limits. It’s not scarce like water or money. It’s within our reach. But if it’s forced, it’s not forgiveness.

“It is good,” Prof Minow warned, “to be cautious about the use of law to deliberately shape or manipulate the feelings of any individual. But it is no less important to admit that law does affect human beings, not just in its results, but in its process.” And then we must take responsibility for how we use that law.

“A government can judge, but only people can forgive.” As Prof Minow’s words lingered, the air suddenly seemed a bit more buoyant.

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