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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

Judge Albie Sachs and Candice Mama discuss traumas of the past and forgiveness in the present
2015-08-05

 

Judge Albie Sachs embraces Candice Mama for her courage in confronting Eugene de Kock, who killed her father.

Two generations. Two stories of triumph. Two South Africans who have displayed immense courage.

Public Dialogue on Trauma, Memory, and Representations of the Past

Judge Albie Sachs and Candice Mama exchanged their experiences of past trauma and subsequent transformation in a public conversation. The event was co-hosted by Prof Pumla Gobodo-Madikizela and The Institute for Justice and Reconciliation (IJR) in Cape Town on Thursday 30 July 2015.

The event was the first instalment in a series entitled Public Dialogue on Trauma, Memory, and Representations of the Past. The theme of the discussion was ‘Intergenerational Dialogue on Trauma and Healing’.

"The aim of these public dialogue events we are co-hosting with IJR is to place the issues of trauma and memory, and the strategies that individuals and communities use to heal, in the public sphere," Prof Gobodo-Madikizela, Senior Research Professor in Trauma, Forgiveness, and Reconciliation Studies at the University of the Free State (UFS) said.

Judge Albie Sachs and Candice Mama in conversation

Former Constitutional Court Judge, Albie Sachs, talked about his participation in South Africa’s liberation struggle, the loss of his right arm in an assassination attempt, and meeting the man responsible – Henri van der Westhuizen. Despite years of exile and extended periods of solitary confinement, Judge Sachs maintains that “we need to acknowledge our history, not be trapped by it.” Judge Sachs also remarked, though, that “we’re seeing too much lamentation, not enough activation.” In a heartrending gesture, Judge Sachs embraced Candice Mama in a hug for her courage in confronting Eugene de Kock, who killed her father.

How poignant then, when Mama said, “I wanted to embrace the brokenness within him,” when she spoke about her meeting with De Kock. By the time I met with Eugene, I could meet him as a human being, not as a villain.” Mama believes that forgiving someone translates into an investment in the person you are forgiving and in your own sanity. She also emphasised the importance of dialogue to move our country forward: “When we share our stories with each other authentically, walls break down.”

This is a stance that Prof Gobodo-Madikizela supports strongly: “When we listen to one another, something unexpected emerges; we encounter the human in each other,” she said. “When we listen with open hearts to each other, we see and experience each other’s humanity.”

Building a bridge between research and society

Referring to the research aspect of the event, Prof Gobodo-Madikizela said that, "in establishing the series of public dialogue events, our vision is to create a bridge between scholarly research and the community at large, on the one hand, and a visual conscience of society, on the other." The UFS is collaborating with the IJR on this research project, which is funded by the Andrew W. Mellon Foundation. The endeavour is led by Prof Gobodo-Madikizela, who also serves as Board Member of the IJR.

 

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