Trash To Treasure: How Materials Engineers In Cali, Colombia Built Better Building Materials




Researchers from the Universidad del Valle School of Engineering are making industrial, construction and demolition waste into useful materials that can provide construction materials with lower carbon emissions.

In the city of Cali, Colombia, more than one million tons of construction and demolition waste are produced each year, which are part of the 22 million tons produced in Colombia nationwide.

Professor Ruby Mejia, leader of the Composite Materials research group within the Faculty of Engineering of the Universidad del Valle, said that the group has been developing different applications of construction and demolition waste, such as recycled aggregates, bricks, blocks, paving stones, tiles, decorative elements, and other construction materials, which satisfactorily meet national standards.

This story is part of our new series of articles showing the work of women research leaders at the Faculty of Engineering in anticipation of Engineering Week 2021, (November 24-26), with the theme of "Women in engineering: research, entrepreneurship and innovation for the development of the region. "

Professor Mejia explained that some of the new material prototypes are possible thanks to the application of new process methodologies such as alkaline activation and geopolymerization.

"Unlike organic polymers, geopolymers are inorganic materials, that is, without carbon, but they are also two-dimensional or three-dimensional networks, depending on the precursor materials used," she said.

Professor Mejia explained that geopolymers are materials that can be produced at a very low temperature (below 100º Celsius) in contrast to the high temperature required to produce conventional materials such as clay bricks, or Portland Cement, where temperatures of more than 1000° Celsius are necessary.

"A great advantage is that geopolymers can be made with less energy consumption and generate lower carbon emissions, in addition to allowing the use of recycled materials, like waste and industrial by-products, as raw materials," Professor Mejía said.

The professor explained that young undergraduate and graduate students have also actively participated in these developments, alongside the professors working in this line of research.

As a result of these works, the group has six patents, some of them jointly with the industrial sector.

Photo: Professor Ruby Mejia, director of the Composite Materials Group. Credit: Edgar Bejarano / Univalle

Circular Economy

Professor Mejia, in the company of Estefania Montoya Quesada, a contractor in one of the current solid waste projects, showed prototypes of the construction materials made in the group´s laboratory.

The appearance of these samples is similar to that of conventional concrete or brick, but nevertheless, they were made from different types of waste such as brick dust or other construction/demolition waste that will usually be disposed of in a landfill.

"The group has focused on strengthening the circular economy model in the industry of the department of Valle del Cauca," explained Montoya Quesada, adding that the work of the group also ensures that successful prototypes comply with the standards so that they can be used.

It should be noted that a study in the US found that about a third of the total weight of construction materials delivered to a job site resulted as waste.



Later on the same day, with great pride, Professor Mónica Villaquirán was showing different samples that were student projects made during the pandemic.

"These bright colors are glass waste collected in a recycling company, there is also brick residue identifiable by its orange color and this material has little cement," said Professor Villaquiran.

Professor Villaquiran said that there is a great opportunity to convert waste into value-added products.

"Each municipality has its own waste management policy, so we are working with the Valle del Cauca environmental authority (CVC) to find alternatives and be able to convert different types of waste into new materials and be able to close the cycle," she explained.

Women in STEM

Globally, there is a huge disparity between the numbers of men and women in Science, Technology, Engineering and Mathematics (STEM).

A 2019 study from the United States found that only 13% of engineering workers were women and the graduation figures for women in a materials degree were the lowest of 10 categories.

According to Professor Mejia, today, a significant number of female researchers with each level of the hierarchy have passed through the Composite Materials Research Group, from her leadership, another professor Monica Villaquiran, who arrived in 2017. There have also been students from undergraduate and postgraduate degrees, both master's and doctorate, which today are linked to the industrial and/or academic sector.

“When I started my teaching career in April 1974, here in materials, I was the only female teacher in the group and there was no other until Professor Monica was hired,” Professor Mejia said.

She added that she is strongly in favor of a meritocratic selection process, but that there has traditionally been a belief that women were unsuitable for engineering work, for example working shifts or on worksites.

"Today, in private industry, there is more representation of women in the plant and in development and research ... we have made some steps forward, but there is more work to do," Professor Mejía said.

Professor Villaquiran said that Prof Mejia was her inspiration.

"It is believed that engineers have to be big guys who wear glasses, boots and sometimes get dirty ... Due to this and the lack of visibility of female models, many girls do not enter engineering because of this stereotype," said Professor Villaquiran, “During my undergraduate degree, Professor Mejia was my role model, I identified with her and did my thesis at the GMC... she has always been my mentor both in undergraduate and graduate, and now as a colleague she is a person that I admire a lot for her leadership, tenacity, management capacity and also because he is a great human being.”

Estefania Montoya Quesada, a contractor with the solid waste project. Credit: Edgar Bejarano / Univalle
   

Other projects of the Composite Materials Group

Other researchers within the Composite Materials Group are working on materials with a lower environmental impact. José Mina, a professor at the School of Materials Engineering, is leading a project on biopolymers derived from agricultural waste from plantains.

“The idea is to have different materials to replace the plastic that we find today in containers, cups, coffee stirrers and other common waste, '' Professor Mina said.

They also have a patent associated with the development of bioactive bone cements with the ability to stimulate bone formation and long fixation times.

Another project is led by Professor Silvio Delvasto, whose objective is the production of high value-added nanostructured materials such as siliceous aerogels from various industrial and agro-industrial waste for thermal and acoustic superinsulation of buildings.

Professor Mejia explained that during the next four years, the Composite Materials Group would also be part of a large 3D printing project to provide better housing in Cauca.

Millions in new resources and lunar technology are "a small step" to build houses in Colombia

During the next four years there will be $ 9.5 billion Colombian pesos (COP) (around $ US 2.5 million) in financing from the General System of Royalties of the department of Cauca, to apply 3D printing using raw materials such as earth, industrial waste, vegetable fibre and other discarded materials.

If you would like to contact the researchers or learn more about the projects, contact the Office of Communications, Faculty of Engineering: comunicaingenieria Correounivalle.edu.co.

Banner photo: Foto: Profesora Mónica Villaquirán, con dos muestras. Crédito: Andrew James/NCC/ Univalle

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