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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

Socially inclusive teaching provides solution to Grade 4 literacy challenges
2017-01-23

 Description: Motselisi Malebese Tags: Motselisi Malebese

Mots’elisi Malebese, postdoctoral Fellow of the Faculty
of Education at the University of the Free State (UFS) tackles
Grade 4 literacy challenges.
Photo: Rulanzen Martin

Imagine a teaching approach that inculcates richness of culture and knowledge to individual learners, thus enhancing equity, equality, social justice, freedom, hope and fairness in terms of learning opportunities for all, regardless of learners’ diversity.

This teaching strategy was introduced by Mots’elisi Malebese, postdoctoral Fellow of the Faculty of Education at the University of the Free State (UFS), whose thesis focuses on bringing together different skills, knowledge and expertise in a classroom environment in order to enhance learners’ competence in literacy.

A teaching approach to aid Grade 4 literacy competency
Titled, A Socially Inclusive Teaching Strategy to Respond to Problems of Literacy in a Grade 4 Class, Malebese’s post-doctoral research refers to an approach that improves listening, speaking, reading, writing, technical functioning and critical thinking. Malebese, who obtained her PhD qualification in June this year, says her research confirmed that, currently, Grade 4 is a bottleneck stage, at which learners from a low socio-economic background fall behind in their learning due to the transition from being taught in their home language to English as a medium of instruction.

Malebese, says: “My study, therefore, required practical intervention through participatory action research (PAR) to create conditions that foster space for empowerment.”

PAR indoctrinates a democratic way of living that is equitable, liberating and life-enhancing, by breaking away from traditional teaching methods. It involves forming coalitions with individuals with the least social, cultural and economic power.

Malebese’s thesis was encouraged by previous research that revealed that a lack of readiness for a transitional phase among learners, teachers’ inability to teach literacy efficiently, and poor parental involvement, caused many learners to experience a wide variety of learning barriers.

A co-teaching model was adopted in an effort to create a more socially inclusive classroom. This model involves one teacher providing every learner with the assistance he or she needs to succeed, while another teacher moves around the room and provides assistance to individual learners.

“Learners’ needs are served best by allowing them to demonstrate understanding in a variety of ways, because knowledge is conveyed and accomplished through collaborative work,” Malebese said.

She believes the most important benefit of this model is assuring that learners become teachers of their understanding and experiences through gained knowledge.

Roleplayers get involved using diverse expertise in their field
Teachers, parents and several NGOs played a vital role in Malebese’s study by getting involved in training, sewing and cooking clubs every weekend and during school holidays. English was the medium of teaching and learning in every activity. A lodge, close to the school, offered learners training in mountain biking and hiking. These activities helped learners become tour guides. Storyteller Gcina Mhlophe presented learners with a gift of her latest recorded storytelling CD and books. Every day after school, learners would read, and have drama lessons once a week.

AfriGrow, an organisation that works with communities, the government and the corporate sector to develop sustainable community-driven livelihoods through agricultural and nutrition programmes, provided learners with seedlings, manure and other garden inputs and training on how to start a sustainable food garden. The children were also encouraged to participate in sporting activities like soccer and netball.

“I was aware that I needed a large toolbox of instructional strategies, and had to involve other stakeholders with diverse expertise in their field,” Malebese said.

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