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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

Kovsie Tennis team defends proud USSA record in Cape Town
2015-12-01


In 2014, Kovsies won gold at the USSA Tennis Tournament for the eighth consecutive time. Six players from last year's 12-man squad are in 2015 in Cape Town again available. Photo: Johan Roux

Duke Munro already has six gold medals from the USSA Tennis Tournament in his cupboard, and the Kovsie Tennis team would wish to bid him farewell in a fitting manner during what will probably be his last tournament in Cape Town.

This year's tournament, taking place from 30 November to 4 December 2015, will probably be Munro's last, since he is completing his Master's degree in Quantity Surveying at the University of the Free State (UFS).

He has competed in the USSA Tournament since 2009, and would like to help his team defend its proud record.

UFS aim for ninth consecutive title

Kovsies have won gold at the USSA Tournament for the last eight years. They are the only team who have been able to win the tournament since the combined format was adopted in 2010. In 2007 and 2008, their Women's team won the tournament, and in 2009, their Men's team.

Kovsies will play in group matches against the Universities of Venda and Wits on 30 November 2015, against the University of Cape Town's (UCT's) second team on 1 December 2015, and against UCT's first team on 2 December 2015. The cross and knockout matches will be played on 3 and 4 December 2015.

Other sporting codes

The Sevens Rugby team from the UFS will compete in the USSA Tournament in George on 30 November and 1 December 2015.

For the past two years, the team has won bronze, and will be playing three league matches on 30 November 2015 against the North-West University's Vaal Campus, Nelson Mandela Metropolitan University's Port Elizabeth Campus, and the Vaal University of Technology.

Kovsies are the current Varsity Sevens Champions after winning the title in Cape Town in April 2015.

Ten Kovsie swimmers took part in the USSA Tournament in Johannesburg from 28 November to 30 November 2015. Last year, Kovsies came third, but unfortunately some of their leading swimmers were unable to take part this year.

The Kovsie Table tennis team will participate in the USSA Tournament in Kimberley from 30 November to 4 December 2015.

Most of the USSA Tournaments in the other sporting codes were either postponed or cancelled because of the recent nationwide student protests. As a result of the protests, exams were written later, and tournaments would have taken place during the holidays.

Only the tennis, table tennis, Sevens rugby, swimming, and cricket B Division in East London will continue.

The USSA Soccer Tournament, to take place at the UFS and the Central University of Technology in Bloemfontein, was postponed until March 2016.

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