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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

UFS professor addresses genetically modified food in South Africa in inaugural lecture
2016-09-23

Description: Chris Viljoen inaugural lecture Tags: Chris Viljoen inaugural lecture

At the inaugural lecture were, from the left front,
Prof Lis Lange, Vice Rector: Academic;
Prof Chris Viljoen; Prof Gert van Zyl,
Dean: Faculty of Health Sciences; back: Prof Marius Coetzee,
Head of Department of Haematology and Cell Biology;
and Dr Lynette van der Merwe, Undergraduate
Programme Director.
Photo: Stephen Collett

The first genetically modified (GM) crops in South Africa were planted in 1998. Eighteen years later, the country is one of the largest producers of GM food in the world. Those in support of genetically modified crops say this process is the only way to feed a rapidly growing world population. But those who criticise GM food describe it as a threat to the environment and safety of the population. Who is right? According to Prof Chris Viljoen of the Department of Haematology and Cell Biology at the University of the Free State, neither position is well-founded.

GM crops play a vital role in food security

While GM crops have an important role to play in increasing food production, the technology is only part of the solution to providing sufficient food for a growing world population. The major genetically modified crops produced in the world include soybean, cotton, maize and canola. However, the authenticity of food labelling and the long-term safety of GM food are issues that consumers are concerned about.

Safety and labelling of GM food important in South Africa
In his inaugural lecture on the subject “Are you really going to eat that?” Prof Viljoen addressed the importance of the safety and labelling of GM food in the country. “In order for food to be sustainable, production needs to be economically and environmentally sustainable. On the other hand, food integrity, including food quality, authenticity and safety need to be ensured,” Prof Viljoen said. 

Labelling of food products for genetic modification was mandatory in South Africa, he went on to say. “It allows consumers the right of choice whether to eat genetically modified foods or not.” The Consumer Protection Act of 2008 requires food ingredients containing more than 5% of GM content to be labelled. 

GMO Testing Facility world leader in food diagnostic testing
In 1999, Prof Viljoen spearheaded research in developing a GM diagnostic testing platform, and in 2003, a commercial diagnostic platform for GM status certification, called the GMO Testing Facility, was founded. The facility is a licensed Eurofins GeneScan laboratory   a world leader in food diagnostic testing   and provides diagnostic detection and quantification of genetically modified organisms (GMOs) in grain and processed foods for the local and international market.

Molecular diagnostic technology the future of food integrity, authenticity and safety
With GM labelling now well-established in South Africa, the next challenge is to establish the use of molecular diagnostic technology to ensure that food integrity, including food authenticity and safety is maintained, said Prof Viljoen.

“To the question ‘Are you really going to eat that?’ the answer is ‘yes’, but let’s continue doing research to make sure that what we eat is safe and authentic.”

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