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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

UFS policies want to help all students

2005-03-09

The death of Hannes van Rensburg, a first-year student from the JBM Hertzog residence, this past weekend, placed various aspects of student life in the spotlight. Dr Natie Luyt, Dean: Student Affairs at the University of the Free State (UFS), and the Student Representative Council (SRC) of the UFS explain which policies are in place to counter these practices.

At all tertiary institutions there are rules and policies to guide students and provide direction for certain behaviour and practices. The same applies to the University of the Free State (UFS).

“At the beginning of the year the UFS provides every residence committee with a manual to establish a framework for meaningful and orderly relations within and among residences on the campus,” said Dr Natie Luyt.

However, it is one thing to set rules, but it is an impossible task to enforce all aspects thereof. Policies currently in place include an alcohol policy, a policy on the induction of first years and a policy on banned practices in residence orientation.

“The alcohol policy was compiled in cooperation with students and their input was constantly asked,” said Dr Luyt. We also liaise on a continuous basis with residences and senior students to encourage the responsible use of alcohol, especially around activities like intervarsities and Rag.

In the policy, recognition is given to the right and voluntary and informed choice of every individual to use alcohol on the UFS campus in a responsible way.

Guidelines for the use of alcohol on campus include among others the following:

Only authorised points of sale will be permitted on campus. In this case it is the various league halls in most of the male residences on campus.

Alcohol will only be made available during fixed times and is not permitted in residence rooms.

All alcohol-related functions are regulated and an application for a temporary alcohol license must be obtained from the Dean: Student Affairs.

The UFS obtained a liquor license in March 2004 which must be administered by senior leagues in various residences on campus. Normal liquor license conditions and the county’s liquor laws apply. Liquor can only be sold to members of the senior league (or special guests) and also to persons over the age of 18 years. Liquor may not be used in public (outside the senior league) or on campus.

The senior leagues may only be open three nights per week and within prescribed times. No liquor could be used in any other place than the senior league halls. Senior leagues could buy liquor from club monies generated by themselves.

The right of senior leagues to serve liquor was suspended by the Rector and Vice-Chancellor the UFS, Prof Frederick Fourie, on Monday 7 March 2005 – pending an investigation of the recent events on campus.

The policy on banned practices include among others that no swearing and shouting at first-years may take place, no first-year student may be targeted individually, no senior may enter the room of a first-year student without an invitation or permission from that first-year student and no senior under the influence of alcohol may have contact with first-year students.

The induction of first-year students takes place by means of three functions, namely an information function (the introduction to the various facets and possibilities of the university system), an induction function (the first-year student becomes involved in various campus and residence activities) and a development function (the first-year student is motivated to take charge of his development potential).

No first-year induction activity may commence before the residence committee’s contracting with the senior students is not completed. This meeting is attended by the residence head and all senior students. The induction policy, residence induction policy of first-year students and first-year rules are discussed.

The senior students sign an attendance list to show that he/she was informed about the policies. A senior who does not sign, may not be involved with any induction session with first-year students.

No physical contact is allowed during the conclusion of the first-year students’ official induction period. The induction of first-year students as full members of the residence is a prestige event, presented by the residence committee. No physical or degrading activities may take place.

The Dean: Student Affairs also has a daily meeting with the primarii of all the residences during the induction period. This helps to monitor the situation and counter any problem behaviour or tendencies.

“Enforced behaviour – where a senior student forces a first-year student to do something against his/her own free wil – is not allowed. Where there is any sign of this, it is met wortel en tak uitgeroei,” said Dr Luyt.

“In any group of people – whether it is a group of students or people at a workplace – there will always be those who will break the rules or those who would like to see how far they could push it.

The SRC, the UFS management and myself are and will stay committed to make each student’s life on this campus a school of learning and an experience which would be remembered for ever,” said Dr Luyt.

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