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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

The influence of load shedding on the evening timetable
2008-01-31

The load shedding that is being applied at present also has a certain influence on especially the evening module and venue timetable. As part of the contingency planning of the UFS, an alternative module and venue timetable has been compiled so that classes that cannot take place during evenings in the week as a result of load shedding can be accommodated on Fridays and Saturdays.

After consultation with students, lecturers will decide whether the alternative timetable will apply when load shedding does indeed occur or whether the alternative timetable will be a permanent arrangement.

The alternative evening module and venue timetable are as follows:

Classes that are presented in the timeslot 18:10 to 21:00 on Thursdays are alternatively accommodated in the same venues at the same times on a Friday. Double or more periods that commence at 17:00, but continue into the period of load shedding are also included in this alternative arrangement.

It is important to note that lecturers who present double periods that start at 14:10 and continue into the period of load shedding must make ad hoc arrangements should they wish to have their periods also included in the alternative timetable.

Classes that take place in the timeslot 20:10 to 22:00 on Wednesdays are alternatively accommodated in the timeslot 08:10 to 12:00 on Saturdays, in a few cases in different venues from those scheduled initially. Double or more periods that start at 18:10, but continue into the period of load shedding are also included in this alternative arrangement.

The venue changes for Wednesday periods that are accommodated on Saturdays are as follows:

  • BLG114 Practical 1 English (A) in the Biology Building 28 from 08:10 to 11:00
     
  • STK114 Practical 1 Afrikaans (D) in West Block 201 from 09:10 to 11:00
     
  • STK114 Practical 1 English (D) in West Block 202 from 09:10 to 11:00
     
  • ALM108 Lecture 1 English (G) in FGG169 from 09:10 to 11:00
     
  • EKN314 Lecture 2 English (A) in the Rindl Hall from 09:10 to 11:00
     
  • EFA112 Lecture 2 Afrikaans (A) in FGG377 from 10:10 to 11:00
     
  • EFK112 Lecture 2 Afrikaans (A) in FGG183 from 10:10 to 11:00
     
  • DLS112 Lecture 2 English (A) in FGG184 from 10:10 to 11:00
     
  • ALC108 Lecture 2 English (E) in the South Block 1 from 10:10 to 11:00
     
  • DLS112 Lecture 2 Afrikaans (A) in the FGG377 from 11:10 to 12:00
     
  • EFA112 Lecture 2 English (A) in FGG183 from 11:10 to 12:00
     
  • EFK112 Lecture 2 English (A) in FGG184 from 11:10 to 12:00
     
  • ELF112 Lecture 2 English (A) in FGG169 from 11:10 to 12:00
     
  • EKN214 Lecture 3 English (A) in Stabilis 4 from 11:10 to 12:00

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