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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

Wag-’n-Bietjie dominates for sixth consecutive year
2016-01-22

Description: First-year athletics Roosmaryn Tags: First-year athletics, Roosmaryn

The First-year Athletics event was a celebration of colour and fun. Besides the athletics on and around the track at Pellies Park on the Bloemfontein Campus, the first-years encouraged their different residences with great enthusiasm.
Photo: Johan Roux

Six out of six.

This is the proud record Wag-’n-Bietjie can boast of after the residence walked away with the women's athletics trophy for the sixth year in a row during the University of the Free State's first-year athletics meeting.

This year's men's winner, Vishuis, attained a hat trick on 20 January 2016 at Pellies Park on the Bloemfontein Campus when the residence was once again named as the athletics champion. Vishuis also won in 2014 and 2015.

What makes Wag-’n-Bietjie's triumph even more remarkable is the fact that the residence ran the fastest, jumped and threw the farthest in eight out of the past nine years. Marjolein won in 2010.

Sonnedou was second, with Roosmaryn and Soetdoring collectively the third women's residences. In the men's division, Legatum and Armentum were second and third respectively.

Sonnedou has the best spirit

The event, a celebration of colour and fun, was characterised by groups of singing first-years yelling their lungs out. The UFS Student Representative Council judges the winners of the different Spirit trophies.

Sonnedou was the overall winner of the Spirit trophy – something even more important than the action on and around the track for some residences.

Sonnedou was named the winner in the division for women's residences, after which the residence was also crowned as overall winner. Welwitschia and Vergeet-My-Nie were second and third respectively in the women's division.

In the men's division, Armentum, who continued singing even when it was raining later in the evening, was the well-deserved winner of the Spirit trophy. Villa Bravado was second with Tswelopele third.

Conlaurês won the Spirit trophy for Co-ed residences, with Imperium and Kagiso second and third respectively.

Wayde a special guest

The Kovsie athlete, Wayde van Niekerk, who also participated in the first-year athletics meeting in his day, was a special guest.

The 400 m athlete, who will represent South Africa at the 2016 Olympics in Rio de Janeiro, was presented to the first-years during the official welcoming ceremony.

Van Niekerk is still the Kovsie record holder in some events, including the 200 m and the 400 m, as well as the 4 x 100 m team relay event.

Team and individual results for the event.

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