A group of civil engineering students at Stellenbosch University (SU) recently took top positions in a national sustainability competition.
The Greenovate Awards 2020, originally scheduled for 4 March 2020, was moved to 21 March 2021 due to the Covid-19 pandemic, according to Rue Munemo, a SU masters student who placed second in the competition. Another SU student, Jean-Pierre Mostert, placed first in the competition.
The competition was run by Growthpoint Properties and the Green Building Council South Africa, said Mapula Matlakala, a sustainability specialist from Growthpoint Properties.
“The award aims to motivate students to be conscious of the communities they create space for,” said Matlakala.
Universities throughout South Africa entered the competition, according to the Greenovate Awards website.
Repurposing ash from Eskom as a building material
Mostert, a masters student in structural engineering, won first place in the engineering category with a project that explored sustainable approaches to the formulation of concrete, according to Mostert.
Jean-Pierre Mostert took first place with a project on biomimicry as an approach to designing the pattern on his “cone-shaped nozzle”. The aim of the nozzle is to pump 3D printed concrete (3DPC) efficiently. PHOTO: Kimberley Schoeman.
In his investigation into 3D printed concrete (3DPC), Mostert used “green materials like fly ash, the byproduct of coal plants in South Africa” and designed a “grooved, cone-like nozzle”, according to Mostert. The project looked at how this method could be used as an efficient and cost-effective way to build low-cost housing in South Africa, said Mostert.
“The difference between traditional concrete and 3DPC is production time, cost, and waste. You just print from an exoskeleton,” said Mostert.
3DPC is more sustainable than normal cement, which produces 5% to 7% of the world’s CO2 emissions, according to Mostert.
According to Mostert’s investigation, Eskom produces 70 000 tons of fly ash per day, and that ash is currently going to waste. “One ton of fly ash produces 50kg of CO2 emissions and is a lot cheaper,” said Mostert.
Illustrating Thixotropy with Ketchup
Rue Munemo’s investigation explored the thixotropy of 3DPC, which describes the most efficient way for concrete to flow, according to Munemo.
According to Rue Munemo, thixotropy of 3DPC can be illustrated using a sachet of ketchup. AUDIO: Kimberley Schoeman.
“You have to design with thixotropy in mind from the very beginning when 3D printing concrete in layers, which are weak in between,” said Munemo. Samples from these layers were observed under a microscope in order to closely examine the strength, she added.
Photo 2: According to Munemo, observing 3DPC at a microscopic level allows for understanding of the failure mode and how best to improve 3DPC’s physical properties. SUPPLIED: Rue Munemo
“With 3DPC, you know how much you need, how long it’s going to take to print, and it doesn’t cause as much waste,” said Rue Munemo. AUDIO: Kimberley Schoeman
Concrete cannot be replaced as a core building material, as it has proven to be durable and efficient, according to Munemo.
“It’s about making what we already have more efficient and going to last, that’s the essence of sustainability,” said Munemo.