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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

“Breakthroughs depend on people believing in their own ideas”

2015-07-23

TED is a renowned international non-profit organisation dedicated to disseminating “ideas worth spreading” in the form compelling talks lasting up to 18 minutes.

Lerothodi Molete’s vision is to witness the youth of Bloemfontein emerge at the forefront of technological, scientific, and entrepreneurial innovations in both South Africa and the global arena.

Molete and Bonginkosi Leeuw are the organisers of TEDxUFS. Their duty is centered on inspiring people to believe in, and express, their ideas. These University of the Free State students have taken it upon themselves to inspire the youth to “push the boundaries of society.”

The second TEDxUFS event to be hosted by the university presents a unique opportunity for students, staff members, and the general public to mingle with influential speakers from across various disciplines.

Details of the event:

Date: Saturday 1 August 2015

Time: 08:00- 18:00

Venue: Albert Wessels Auditorium, Bloemfontein Campus

The keynote speakers include: Mmusi Maimane (Federal Leader: Democratic Alliance), Gareth Cliff (Radio personality: Cliff Central), Pieter Geldenhuys (Futurist), Brian Kally (Director: Arrow Logistics), Jonathan Jansen (Vice-Chancellor and Rector: UFS), Ricardo Peach (Director: Vrystaat Arts Festival, Pamela Nomvete (Former actor and writer), Gil Oved (Founder: Creative Counsel), Pepe Marais (CEO: Joe Public), Angelo Mockie (Senior Officer: Student Affairs and musician), Philippa Tumubweinee (Senior Lecturer in Architecture: UFS), and Melody Mentz (Psychology Senior Professor: UFS).

The reason behind the #AskWhy theme

"Why is a small word but it’s a quick, broad, sharp and abrupt one,” explains Leeuw. “It is the chosen word of the non-conformist, the defiant, and the visionary. It is a confrontational word. It challenges what is thought to be impossible.”

The ability to interrogate reality is what society and economies are built on. The absence of the fear to question encourages the capacity to progress.

Motivating young people to follow their dreams is the reason why the TEDxUFS team is persistent in their endeavours. Molete believes that, in order to change anything, people need to ask why.

Background of the innovation powerhouse called TED(x)

TED is a renowned international non-profit organisation dedicated to disseminating “ideas worth spreading” in the form compelling talks lasting up to 18 minutes.

In 1984, it was introduced as a conference exploring Technology, Entertainment, and Design. Three decades later, TED covers a wide variety of topics of global significance, reflecting the contemporary era in more than 100 languages.

TEDx events are under the TED umbrella. These events are organised independently, and create a platform for deliberating on local matters. The programme assists communities, organisations, and individuals to stimulate critical dialogue.

On 25 July 2014, the UFS hosted its inaugural TEDxUFS conference at the Odeion theatre on the Bloemfontein Campus, where eleven speakers addressed an audience of 150 people on interdisciplinary topics ranging from economics to entrepreneurship, technology, art, design, and theology.

This year, 200 seats will be available for innovative revolutionary individuals in search of inspiration.

Tickets are available at 0619284253 / 079 381 4126. Prices: R80 (Student/scholars) and R350 (Public/staff)

LINKS:

Lerothodi Molete- http://whoswho.co.za/lerothodi-molete-742022

Bonginkosi Leeuw- https://www.ted.com/tedx/events/10499

TEDxUFS- http://kovsielife.ufs.ac.za/templates/archive.aspx?news=276

Mmusi Maimane- http://whoswho.co.za/mmusi-maimane-44612

Garett Cliff- http://www.garethcliff.com/

Pieter Geldenhuys- http://pietergeldenhuys.com/

Brian Kally- https://za.linkedin.com/pub/brian-kally/4b/888/959

Jonathan Jansen- http://www.ufs.ac.za/adhoc-pages/rectorate/prof-(jd)-jonathan-jansen

Ricardo Peach- http://ricardopeach.com/

Pamela Nomvete- http://whoswho.co.za/pamela-nomvete-4789

Gil Ovid- https://za.linkedin.com/pub/gil-oved/3/910/892

Pepe Marais- http://joepublic.co.za/people

Angelo Mockie- https://za.linkedin.com/pub/angelo-mockie/27/56/302

PhilippaTumubweinee- http://natagri.ufs.ac.za/templates/staffmember.aspx?DCode=101&pid=zyNJm7KI%2b1k%3d

Melody Mentz- https://za.linkedin.com/in/melodymentz

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