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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

Bullying in schools: Everyone’s problem
2005-06-03

From left:  Prof Gerhardt de Klerk, Dean: Faculty of the Humanities; Prof Corene de Wet; Prof Rita Niemann, Head of the Department of Comparative Education and Educational Management in the School of Education and Prof Frederick Fourie, Rector and Vice-Chancellor of the UFS

It is not only learners who are the victums of bullying in schools, but also the teachers. Prof. Corene de Wet from the Department Comparative Education and Educational Management at the University of the Free State reported, against the background of two studies on bullying in Free State secondary schools, that bullying is a general phenomena in these schools.

Prof. de Wet, who delivered her inaugural lecture on Wednesday night, is from the Department Comparative Education and Educational Management which resorts under the School of Education at the University of the Free State. She is the first women who became a full professor the School of Education.

Prof. de Wet says, “A student is being bullied or victimized when he or she is exposed, repeatedly and over time, to negative action on the part of one or more students. Bullying always includes the intentional use of aggression, an unbalanced relationship of power between the bully and the victim, and the causing of physical pain and/or emotional misery.

In some Free State schools there are victims and perpetrators of direct and indirect verbal, as well as emotional, physical and sexual bullying.

“Adults who say that bullying are part of the growing-up process and parents who set not only academic expectations but also social expectations to their children cause that victims are unwilling to acknowledge that they are being bulled. Many parents are also unaware of the levels of bullying their children are exposed to.

“Some of the learners were at least once a month the victim of direct verbal harassment, 32,45% were assaulted by co-learners and 11,21% of them were at east once per week beat, kicked, pushed and hurt in any other physical way. Free State learners are very vulnerable to bullies at taxis and on the school yard they are mostly exposed to bullies in bathrooms.

“Learners are usually bullied by members of the same gender. However, racial composition also plays a role in some Free State schools. A grade 12 girl writes, ‘There are boys in my school who act means against black people. When the teacher is out they take a red pen and write on the projector and spray it with spirits. It looks like blood and they would say it is AIDS and my friends and I have it.’

“Educators must take note of bullying in schools and must not shrug it off as unimportant. Principals or educators could be find guilty of negligence. A large number of educator respondents, 88,29%, indicated that they would intervene in cases of verbal bullying and 89,71% would intervene if they saw learners being physically bullied. However, only 19,97% of the learners who were victims of bullying were helped by educators/ other adults from their respective schools.

“The learners’ lack of trust in their educators’ abilities and willingness to assist them in the fight against bullying has important implications for education institutions. The importance of training must be emphasised.

Learners bully their educators to undermine their confidence. In Prof. de Wet’s study on educator-targeted bullying in Free State schools 24,85% of the respondents were physically abused by their learners, 33,44% were the victims of indirect verbal bullying, and 18,1% were at one time or another sexually harassed by their learners. These learner offences may lead to suspension.

“Educators are not only victims of bullying; some of them are the bullies. The South African Council for Educators prohibits bullying by educators. It is worrying that 55,83% of the educators who participated in the research project verbally victimised learners, 50,31% physically assaulted learners and a small percentage was guilty of sexual harassment.

“Every educator and learner in South Africa has the right to life, equal protection and benefit of the law, of dignity, as well as of freedom and security of the person. These rights will only be realised in a bully-free school milieu.

“To oppose bullying a comprehensive anti-bullying programme, collective responsibility and the establishment of a caring culture at schools and in the community is necessary,” said Prof. de Wet.
 

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