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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

Johann swims his way to Olympics
2016-05-18


Johann van Heerden from the University of the Free State has qualified for the Paralympic Games in the swimming pool, and is now waiting to hear if he will be included in the South African team. Photo: Nadya van Heerden.

In the past couple of months, Johann van Heerden has been swimming his way to the Paralympic Games, and is still preparing as if he will be going to Rio de Janeiro.

The Kovsie swimmer, who will know whether he has been included in the Paralympic team in July 2016, feels his training is progressing well. The Olympics will be held in Brazil from 7 to 18 September 2016. If all goes well, this could be the first of several Olympics for the 20-year-old second-year Education student from the University of the Free State (UFS).

Dream year for Education student

Van Heerden (cerebral palsy), whose hero is the former Paralympic superstar Natalie du Toit, has had huge successes in the run-up to the 2016 Olympics. Among others, he was named the best senior swimmer at the Nedbank National Championships for the Physically Disabled in Bloemfontein in March 2016. At the South African Senior Championships in Durban in April 2016, he qualified for the Olympics in the 100 m breast-stroke with an A-qualifying time, and in the 50 m and 100 m freestyle with B-qualifying times.

Only three male swimmers to Olympics

However, he has to wait until the announcement of the South African Paralympic team, since only three male and three female swimmers will be selected. He will not be competing in another major event before the Olympics. “My short-term goal is to compete in this year’s Games, and, in the long term, I would like to reach even greater heights at the 2020 Games,” he said. Du Toit is an inspiration to him because “she was hard-working, and she had a lot of drive”.

Other students from CUADS also excel

At the above-mentioned National Championships, Van Heerden won a total of five gold medals (200 m medley, 100 m breaststroke, 50 m freestyle, 50 m breaststroke, and 200 m breaststroke) and one silver medal (100 m freestyle). Other students from the Center for Universal Access and Disability Support at the UFS also excelled.

Dineo Mokhosoa (cerebral palsy) won three gold medals (long jump, shot-put, and discus), while the athlete Louzanne Coetzee (blind) shattered the world record in the 5 000 m, as well as the Africa record in the 1 500 m. Juanré Jenkinson (cerebral palsy) won two silver medals (discus and shot-put) while Danie Breitenbach (blind) won two gold medals (800 m and 1500 m).

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