NOVEMBER 16, 2022
Professor seeks to turn trash into new, sustainable structures
Buildings that face demolition could soon be transformed into a new type of concrete that would be used to create new structures, an approach that reduces landfill waste and creates jobs.
It’s the revolutionary vision of Julie Hartell, an assistant professor of construction science, who is poised to give old building materials a new lease on life with her work in the Center for Infrastructure Renewal Lab at Texas A&M.
Inspired by her experience as a structural engineer working on urban structures with durability issues in her hometown of Montreal, Hartell pursued a master’s degree in infrastructure rehabilitation and then a Ph.D. focusing on concrete material durability and sustainability.
Her research and newfound passion led her to teach at American universities, where she realized that a massive solution was necessary to reduce waste in the industry.
“As much as I love concrete, it is a wasteful material, because we don’t have adequate recycling technologies yet,” she said.
A 500 million-ton problem
“Construction and demolition waste is the number one waste producer in the United States,” said Hartell. “Our industry, I hate to say it, is a massive polluter and it’s a big problem. Every municipality with a landfill is adversely affected by the accumulation of construction and demolition waste.”
The creation of concrete materials is also terrible for the environment, as it’s one of the largest contributors in terms of carbon emissions and carbon footprint.
“We’re looking at over 150 million tons of material that’s being disposed in landfills per year,” she said. “This represents a viable source for aggregates that we could incorporate into new concrete mixtures.”
Destruction from natural hazards such as hurricanes and tornados adds more building debris to landfills.
While teaching at Oklahoma State University, Hartell saw the devastation caused by hurricanes in Texas and nearby coastal regions. “I could not believe that the only solution we had was to landfill everything and do it all again from scratch,” she said.
The destruction dilemma
Current processes for reusing materials from existing structures aren’t viable for most construction projects due to extensive time, effort and costs associated with salvaging usable pieces.
To reuse elements of a structure, workers either salvage usable pieces like doors, windows and material before demolition, or sort through the debris afterwards to recover elements like steel and concrete for recycling. But getting materials to the point where they can be re-utilized can be more effort than it’s worth.
“Steel is a high-dollar value recycling material, so you want to remove as much steel as possible, but you also have to separate it from the concrete,” Hartell said. “It takes time, effort, different types of equipment, and there is cost associated with that and in sorting the debris.”
This cost ends up making products from recycling materials about 40 percent higher than just using new products, said Hartell. If buying new is the cheaper option, there’s no incentive for consumers or the industry to deal with the waste.
Global problem, circular solution
Hartell thinks she has a solution to reuse without the extensive sorting or legwork — just pulverize the whole thing.
“We’d smash it,” Hartell said with a grin.
“Everything. The building, the doors, the carpets, the lighting, the ceramic, the toilet — we’d take it all, crush it and nothing goes to landfill. We’d smash and smash and smash until we have a very, very, very small particle the same size as sand.”
Like a granular circle of life, everything has a purpose and goes on to become renewed. The sand-size particles, in Hartell’s scenario, would have water, cement and chemicals added to them to create a new concrete material.
Some of the crushing technology already exists, but it hasn’t been used in this way due to the varying components in existing concrete mixes. Also, advances in chemistry would be needed to create an effective, stable concrete or other material with the aggregate.
To pin down the processing, Hartell and her research team are using a $25,000 grant from the Texas A&M Construction Industry Advisory Council to explore large-scale equipment that could process different parts of a structure down to a desirable shape and size.
“We may come up with brand new equipment or use something already on the market,” she said. “It’s really fun to explore the scholarly side of how to go about this and make the desired end product low cost.”
Another battle they’ll have to face is the general stigma associated with reusing materials, as many consumers assume that recycled products will be of lesser quality.
“There’s wear and tear, there’s potential durability issues. It’s is very hard to control the end quality and have a really good understanding of what that aggregate is,” said Hartell. “The different compositions of materials mean that extensive testing needs to be done to prevent chemical interactions, volumetric or durability issues. It’s like a really big chemistry problem.”
But advancing technology and the potential net positives for the environment, cost, and waste streams make now the perfect time to conduct this research and help shape the future of the industry, she said.
“There’s a future where we can not only limit waste, but also reduce carbon footprint because we no longer have to transport all the material,” she said. “We use fewer raw materials, less energy, less water. It extends the life cycle of existing materials and prevents potential pollutants from going into our environment because we’re rebinding them and securing them in a new building block.”
Hartell’s vision eliminates transport cost and associated emissions by doing all the processing of materials and creation of new concrete on the demolition site.
“The building is demolished on site and we have a processing plant on site,” she said. “We can bring in a mobile plant to make new concrete units from the demolished buildings, and then we can rebuild on site.”
The work of processing the materials, doing the calculations and science to create a stable aggregate and mixing the new concrete could also create an entire new market of recycling/ construction industry jobs.
“This is a new product that can lower the cost of construction and can be scaled up in every single municipality. We’re looking at the creation of a potential new, trillion-dollar economy for the United States and a new workforce,” she said. “According to a recent Environmental Protection Act report, currently a worker in the recycling industry makes approximately $70,000 a year. For every 1000 tons, you need a person, so that would potentially be several hundred thousand good-paying jobs.”
Saving money, making money
Because companies currently have to pay to load, haul, drive and dump construction waste at landfills, Hartell says a huge advantage to her concept is that the demo material will be nearly free to use, at least at first.
“In our current business model, if we can take the material off their hands for less than they’d pay to dispose of the materials, then they save money and don’t have to deal with it,” said Hartell. “Meeting with various demolition companies, they said they’d be willing to give it away for free or cheap and think it’s a fantastic idea.”
She said that would help immensely with the initial costs of processing and creating a new material at a low cost, but if her initiatives are successful, she said demolition companies would almost inevitably opt to charge for the debris.
“There always has to be someone out of the gate. First there was Netflix and now there’s everybody else,” she said. “But if you’re suddenly bringing value to waste, that’s a good thing. It means you’re disrupting the current disposal cycle and there are going to be fewer people sending things to landfill if that waste can be reused.”
Hartell says she’ll start showing the public and industry that this unconventional material can be used, while strategizing to create a business model over time.
“The goal is to bring the cost at least to parity with new aggregate,” she said. “We need to push the construction industry more towards concepts of sustainability.”
From Scrap to Shelves
Funded by several grants from the National Science Foundation’s I-Corps program, VentureWell, and private entities, Hartell hopes to progress from their current research to prototyping, scaling, and implementation within the next decade.
“We are hoping to be able to increase the proof of concept to viable product in the following two to three years,” she said. “And, and then with that, in the next phases of development, to have an implementable product/process in about a five to ten-year range.”
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