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Green Engineering: How UFS’s Green concrete can be an alternative to OPC cement

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

Researchers international leaders in satellite tracking in the wildlife environment

2015-05-29

Ground-breaking research has attracted international media attention to Francois Deacon, lecturer and researcher in the Department Animal, Wildlife and Grassland Sciences at the UFS, and Prof Nico Smit, from the same department. They are the first researchers in the world to equip giraffes with GPS collars, and to conduct research on this initiative. Recently, they have been joined by Hennie Butler from the Department of Zoology as well as Free State Nature Conservation to further this research.

“Satellite tracking is proving to be extremely valuable in the wildlife environment. The unit is based on a mobile global two-way communication platform, utilising two-way data satellite communication, complete with GPS systems.

“It allows us to track animals day and night, while we monitor their movements remotely from the computer. These systems make possible the efficient control and monitoring of wildlife in all weather conditions and in near-to-real time. We can even communicate with the animals, calling up their positions or changing the tracking schedules.

“The satellite collar allows us to use the extremely accurate data to conduct research with the best technology available. The volume of data received allows us to publish the data in scientific journals and research-related articles.

“Scientific institutions and the public sector have both shown great interest in satellite tracking, which opens up new ground for scientific research for this university. Data management can be done, using Africa Wildlife Tracking (AWT) equipment where we can access our data personally, store it, and make visual presentations. The AWT system and software architecture provide the researcher with asset tracking, GPS location reports, geo-fencing, highly-detailed custom mapping, history reports and playback, polling on demand, history plotting on maps, and a range of reporting types and functions,” Francois said.

Data can be analysed to determine home range, dispersal, or habitat preference for any specific species.

Francois has been involved in multiple research projects over the last 12 years on wildlife species and domesticated animals, including the collaring of species such as Black-backed Jackal, Caracal, African Wild Dog, Hyena, Lion, Cheetah, Cattle, Kudu, Giraffe, and Black Rhino: “Giraffe definitely being the most challenging of all,” he said.

In 2010, he started working on his PhD, entitled The spatial ecology, habitat preferences and diet selection of giraffe (Giraffa camelopardalis giraffa) in the Kalahari region of South Africa.

Since then, his work has resulted not only in more research work (supervising four Masters students) but also in a number of national and international projects. These include work in the:

Kalahari region (e.g. Khamab Nature Reserve and Kgalagadi Transfrontier Park)
Kuruman region (Collared 18 cattle to identify spatial patterns in relation to the qualities of vegetation and soil-types available. This project took place in collaboration with Born University in Germany)
Woodland Hills Wildlife Estate and Kolomella Iron Ore – ecological monitoring
A number of Free State nature reserves (e.g. Distribution of herbivores (kudu and giraffe) and predators (camera traps)

Francois is also involved with species breeding programmes and management (giraffe, buffalo, sable, roan, and rhino) in Korrannaberg, Rustenburg, Hertzogville, Douglas, and Bethlehem as well as animal and ecological monitoring in Kolomella and Beesthoek iron ore.

Besides the collaring of giraffes, Francois and his colleagues are involved in national projects, where they collect milk from lactating giraffes and DNA material, blood samples, and ecto/endo parasites from giraffes in Southern Africa.

With international projects, Francois is working to collect DNA material for the classification of the nine sub-species of giraffe in Africa. He is also involved in projects focusing on the spatial ecology and adaptation of giraffe in Uganda (Murchison Falls), and to save the last 30 giraffe in the DRC- Garamba National Park.

This project has attracted a good deal of international interest. In June 2014, a US film crew (freelancing for Discovery Channel) filmed a documentary on Francois’ research (trailer of documentary). Early in 2015, a second crew, filming for National Geographic, also visited Francois to document his work.

More information about Francois’ work is available at the GCF website.

Read Francois Deacon's PhD abstract

Direct enquiries to news@ufs.ac.za.

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