WEST LAFAYETTE, Indiana – Concrete is not glamorous. It's the building materials workhorse: versatile, durable, and almost universally ubiquitous, with 30 billion tons of concrete produced each year. Cement, a component of concrete, produces 8% of the world's carbon footprint.
Looking to reduce that percentage, Purdue University engineers have discovered a way to make concrete more sustainable. His new recipe for concrete has the potential to dramatically reduce carbon emissions, creating pillars for a better world.
A team led by Mirian Velay-Lizancos, an assistant professor of civil engineering at Purdue, proposes adding small amounts of nanoscale titanium dioxide to the cement paste that makes up concrete. The team found that titanium dioxide, a powdered substance best known for its uses in sunscreens, paints, plastics, and food preservatives, enhances the natural ability of concrete to sequester carbon dioxide.
The team found that adding only small amounts of nano-titanium dioxide nearly doubles the concrete's absorption of the problematic greenhouse gas. The study recently appeared in the scientific journal Construction and Building Materials. A YouTube video of the work is available.
Velay-Lizancos studies concrete and works to turn it into a more sustainable building material. Concrete, a variable mix of water, cement paste, and aggregates such as sand and gravel, was invented millennia ago. Since then, it has changed to adapt to the changing needs of civilizations and the materials available. The concrete of the pyramids needed to withstand heat and wind. The concrete in Roman aqueducts needed to carry millions of gallons of water. Modern concrete must be strong, durable, inexpensive and as sustainable as possible. Making concrete is an energy and resource intensive process. Traditional concrete naturally absorbs carbon dioxide, but not very much or very quickly.
"We cannot wait decades for concrete to absorb the carbon dioxide produced in its manufacturing process," Velay-Lizancos said. “My team is making the concrete itself absorb carbon dioxide faster and in higher volumes. We are not trying to change the way we use concrete; we are making concrete work for us. "
The staggering amount of concrete in use around the world today (in bridges, roads and infrastructure, in buildings and monuments, dams and pipe systems) means that any slight improvement in concrete's carbon footprint could have massive effects worldwide.
The changes Velay-Lizancos' team proposes would result in more than a small change. Their research indicates that Including titanium dioxide in the cement mix used to make concrete can double the amount of carbon dioxide that it naturally sequesters in the same amount of time. This effect adds to the well-studied photocatalytic effect of concrete, in which light Ultraviolet from the sun interacts with concrete to help concrete oxidize harmful nitrogen oxide gases into nitrates.
"We live in a construction environment," he said Velay-Lizancos. “There is no doubt that improving the sustainability of concrete, the most widely used construction material in the world, would be a great step towards sustainable development.”
Initially, Velay-Lizancos and two of his PhD students, Carlos Moro and Vito Franciosa, were studying how titanium dioxide might interact with cement to strengthen concrete and how curing temperature might affect those interactions. They noted that some of their concrete samples that included nano-titanium dioxide absorbed carbon dioxide from the surrounding air faster than other samples.
Subsequent research revealed that adding nano-titanium dioxide to the concrete mix decreased the size of the calcium hydroxide molecules, making it much more efficient at absorbing carbon dioxide than other cement pastes. The addition accelerated the rate of carbon absorption and increased the total volume of carbon dioxide it can absorb.
"I've always wanted to help others, do something meaningful, something shocking," Velay-Lizancos said. “This job is a way that I can help others. Our research can lead to lower net carbon dioxide emissions. Knowing what you are doing can help stop climate change makes you wake up every day with energy to work harder than the day before. ”
Your future research will focus on more ways to make concrete more sustainable, more durable, and an even better building material for the future.
About Purdue University
Purdue University is a leading public research institution developing practical solutions to today's toughest challenges . Ranked # 5 Most Innovative University in the United States by U.S. News & World Report, Purdue offers world-changing research and out-of-this-world discoveries. Committed to practical, online learning, in the real world, Purdue offers a transformative education for all. Committed to affordability and accessibility, Purdue has frozen tuition and most fees at the 2012-13 levels, allowing more students than ever to graduate debt-free. See how Purdue never stops in persistent pursuit of the next big leap at https://purdue.edu/.[19459003
Writer, media contact: Brittany Steff; 765-494-7833; firstname.lastname@example.org
Source: Mirian Velay-Lizancos email@example.com
Journalists visiting the campus ]: Journalists must follow Protect Purdue protocols and the following guidelines:
- The campus is open, but the number of people in the spaces may be limited. We will be as accommodating as possible, but you may be asked to leave or introduce yourself from another location.
- To allow access, particularly to campus buildings, we recommend that you contact the Purdue News Service media contact listed in the release to inform them of the nature of the visit and where you will be visiting. A representative from the News Service can facilitate secure access and accompany you to campus.
- Correctly wear masks inside any building on campus, and correctly wear masks outdoors when a social distance of at least six feet is not possible.
CO modification 2 capture and pore structure of hardened cement paste made with nano-TiO 2 addition: Influence of the water-cement and CO ratio 2 age of exposure
Carlos Moro, Vito Franciosa, Mirian Velay-Lizancos
DOI: 10.1016 / j.conbuildmat.2020.122131
This article studies the effects of nano-TiO2 in CO2 sequestration of hardened cement paste, depending on the water-cement ratio (a / c) and the structure of the pores. Twelve cement paste mixtures were prepared with four different percentages of nano-TiO2 (0%, 0.5%, 1%, 2%) and three p / c (0.45, 0.50, 0.55). The samples were exposed for 24 hours to a CO2 environment at two different ages (14 and 28 days). Thermogravimetric analyzes and 3D X-ray scans of pore structure were performed on exposed and unexposed samples. The results showed that nano-TiO2 produces an improvement in the absorption of CO2 up to a certain percentage. This maximum percentage depends on the age of exposure and w / c. Nano-TiO2 produces a reduction in porosity and an increase in the reactivity of calcium hydroxide (CH), which have opposite effects on the absorption of CO2. These two competing mechanisms may explain why nano-TiO2 can be beneficial or detrimental to CO2 absorption depending on the w / c ratio and age.