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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

Twenty years of the constitution of South Africa – cause for celebration and reflection
2016-05-11

Description: Judge Azar Cachalia Tags: Judge Azar Cachalia

Judge Azar Cachalia

The University of the Free State’s Centre for Human Rights and the Faculty of Law held the celebration of the twentieth anniversary of the adoption of the South African Constitution on 11 May 2016 on the Bloemfontein Campus.  Students and faculty members celebrated and reflected on not only the achievements of the constitution but also on perspectives regarding its relevance in modern society, and to what extent it has upheld the human rights of all citizens of South Africa.

The panel discussion started with a presentation on the pre-1996 perspective by Judge Azar Cachalia of the Supreme Court of Appeal.  Judge Cachalia reflected on his role in the realisation and upholding of the constitution, from his days as a student activist, then as an attorney representing detainees during political turmoil, and currently as a judge: “My role as an attorney was to defend people arrested for public violence. My role as a judge today is to uphold the constitution.”  He stressed the importance of the constitution today, and the responsibility institutions such as the police service have in upholding human rights.  Judge Cachalia played a significant role in drafting the new Police Act around 1990, an Act which was to ensure that the offences perpetrated by the police during apartheid did not continue in the current democratic era. Further, he pointed out that societal turmoil has the potential to make society forget about the hard work that was put into structures upholding human rights. “Constitutions are drafted in moments of calm.  It is a living document, and we hope it is not torn up when we go through social conflict, such as we are experiencing at present.”

Thobeka Dywili, a Law student at the UFS, presented her views from the new generation’s perspective.  She relayed her experience as a student teaching human rights at schools in disadvantaged communities. She realised that, although the youth are quite aware of their basic human rights, after so many years of democracy, “women and children are still seen as previously disadvantaged when they should be equal”. She pointed out that, with the changing times, the constitution needs to be looked at with a new set of eyes, suggesting more robust youth engagement on topics that affect them, using technology to facilitate discussions. She said with the help of social media, it is possible for a simple discussion to become a revolution; #feesmustfall was a case in point.

Critical perspectives on the constitution were presented by Tsepo Madlingozi of University of Pretoria and University of London. In his view, the constitution has not affected policy to the extent that it should, with great disparities in our society and glaring issues, such as lack of housing for the majority of the poor.  “Celebration of the constitution should be muted, as the constitution is based on a decolonisation approach, and does not directly address the needs of the poor. The Constitutional Court is not pro-poor.”  He posed the question of whether twenty years on, the present government has crafted a new society successfully.  “We have moved from apartheid to neo-apartheid, as black elites assimilate into the white world, and the two worlds that exist have not been able to stand together as a reflection of what the constitution stands for.”

Prof Caroline Nicholson, Dean of the Faculty of Law, encouraged more open discussions, saying such dialogues are exactly what was intended by the Centre for Human Rights. She emphasised the importance of exchanging ideas, of allowing people to speak freely, and of sharing perspectives on important issues such as the constitution and human rights.

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