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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 to investigate implementation of quality-monitoring system for SA food industry

2006-02-07

Some of the guests who attended the workshop were from the left Prof James du Preez (Chairperson: Department of Biotechnology at the UFS); Prof Lodewyk Kock (Head: South African Fryer Oil Initiative (SAFOI) at the UFS)); Mrs Ina Wilken (Chairperson: South African National Consumer Union (SANCU)); Prof Herman van Schalkwyk (Dean: Faculty of Natural and Agricultural Sciences at the UFS) and Mr Joe Hanekom (Managing Director of Agri Inspec).
Photo: Stephen Collet

UFS to investigate implementation of quality-monitoring system for SA food industry

The University of the Free State (UFS) will be investigating the implementation of a quality-monitoring service for the South African food industry.

This was decided during a workshop to discuss the external quality monitoring in the edible oil industry of South Africa, which was recently held at the UFS.

Major role players in the fast-food sector like Nando's, Spur, Captain
Dorego's, King Pie Holdings, Black Steer Holdings, etc and various oil
distributors like Felda Bridge Africa, Refill Oils, PSS Oils and Ilanga Oils attended
the workshop. Also present was Mrs Ina Wilken, Chairperson of the South African National Consumer Union (SANCU) and key-note speaker of this workshop. She represented the consumer.

These role players all pledged their support to the implementation of this quality- monitoring system for the whole food industry.

The decision to implement this system follows the various malpractices reported in the press and on TV concerning food adulteration (eg the recent Sudan Red Scare), misrepresentation (eg olive oil scandal exposed in 2001) and the misuse of edible frying oils by the fast-food sector.

“One of the basic rights of consumers is the right to safe food. Consumers must be protected against foods and food production processes which are hazardous to their health. Sufficient guarantee of the safety of all food products and food production processes should be implemented. It does not help to have adequate food standards and legislation and there is no manpower to do the necessary investigation or monitoring,” said Mrs Wilken.

The South African Fryer Oil Initiative (SAFOI), under the auspices of the UFS Department of Microbial, Biochemical and Food Biotechnology, currently monitors edible oils in the food industry and makes a seal of quality available to food distributors.

“Last week’s decision to implement the quality-monitoring system implies that we will now be involving also other departments in the UFS Faculty of Natural and Agricultural Sciences who are involved in various aspects of the food chain in an endeavor to implement this quality monitoring system,” said Prof Herman van Schalkwyk, Dean: Faculty of Natural and Agricultural Sciences at the UFS and one of the main speakers at the workshop.

Prof van Schalkwyk said that the main aim of such a system will be to improve the competitiveness of the South African food industry. “It is clear that the role players attending the workshop are serious about consumer service and that they agree that fraudulent practice should be monitored and corrected as far as possible. Although some of the food outlets have the capacity to monitor the quality of their food, it may not seem to the consumer that this is an objective process. The proposed external monitoring system would counteract this perception amongst consumers,” said Prof van Schalkwyk.

The workshop was also attended by representatives from SAFOI and Agri Inspec, a forensic investigation company collaborating with inter-state and government structures to combat fraud and international trade irregularities.

Agri Inspec has been working closely with SAFOI for a number of years to test the content of edible oils and fats. “Extensive monitoring and control actions have been executed in the edible oil industry during the past four years to ensure that the content and labeling of oil products are correct. Four years ago almost 90% of the samples taken indicated that the content differed from what is indicated on the label. This has changed and the test results currently show that 90% of the products tested are in order. However, to maintain this quality standard, it is necessary that quality monitoring and educational campaigns are continuously performed,” said Mr Joe Hanekom, Managing Director of Agri Inspec.

“The seal of quality presented by SAFOI should also be extended to include all the smaller oil containers used by households,” Mrs Wilken said.

The SAFOI seal of quality is currently displayed mainly on some oil brands packed in bigger 20 liter containers, which include sunflower oil, cottonseed oil, palm oil etc which are used by restaurants and fast food outlets. “Any oil type is eligible to display the seal when meeting certain standards of authenticity. In order to display the seal, the distributor must send a sample of each oil batch they receive from the manufacturer to SAFOI for testing for authenticity, ie that the container’s content matches the oil type described on the label. This is again double checked by Agri Inspec, which also draws samples countrywide from these certified brands from the end-user (restaurant or fast food outlets). If in breach, the seal must be removed from the faulty containers,” said Prof Lodewyk Kock, Head of SAFOI.

“It should however be taken into account that oils without a seal of quality from the UFS can still be of high quality and authentic. Other external laboratories equipped to perform effective authenticity tests may also be used in this respect,” said Prof Kock.

“It is also important to realise that any oil type of quality such as sunflower oil, cottonseed oil, palm oil etc can be used with great success in well controlled frying processes,” he said.

Further discussions will also be held with the Department of Health, the SA National Consumer Union and Agri Inspec to determine priority areas and to develop the most effective low-cost monitoring system.

More information on the UFS oil seal of quality and oil use can be obtained at www.uovs.ac.za/myoilguide

Media release
Issued by: Lacea Loader
Media Representative
Tel: (051) 401-2584
Cell: 083 645 2454
E-mail: loaderl.stg@mail.uovs.ac.za
6 February 2006

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