Researchers Add Titanium Dioxide to Cement
Engineers at Purdue University say they have discovered a way to make concrete more sustainable—by adding small amounts of nanoscale titanium dioxide to the cement.
Mirian Velay-Lizancos, an assistant professor of civil engineering at Purdue, along with her team, just published a study in the journal Construction and Building Materials about the mixture, which the researchers say nearly doubles concrete’s absorption of greenhouse gas.
About the Findings
“We can’t 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 greater volumes. We’re not trying to change the way we use concrete; we’re making the concrete work for us.”
Initially, Velay-Lizancos and two of her doctoral students, Carlos Moro and Vito Francioso, were studying how TiO2 might interact with cement to make concrete stronger and how curing temperature might affect those interactions.
However, during their experiments, they noticed that some of the concrete samples that included nano-titanium dioxide absorbed carbon dioxide from the surrounding air faster than other samples.
The photocatalytic effect in concrete is when the ultraviolet light from the sun interacts with the concrete to help oxidize nitrogen oxide gases into nitrate. Velay-Lizancos’ research indicates that including the small amount of TiO2 could make the concrete double the amount of carbon dioxide that it naturally sequesters over time.
“We are living in a building environment,” Velay-Lizancos said. “There is no doubt that improving the sustainability of concrete, the most used construction material in the world, would mean a giant leap for sustainable development.”
Her research on the sustainability and durability of concrete is ongoing.
Other Concrete Studies
In December, a team of researchers across a variety of universities reported that they were collaborating to resolve issues with how tunnel service lives are being determined.
Specifically, Florian Mittermayr, researcher at the Institute of Technology and Testing of Construction Materials at Graz University of Technology said that, "The service life is currently calculated on the basis of theoretical key figures and empirical values. Environmental conditions such as chemically aggressive groundwater, for example, can possibly lead to cost-intensive maintenance measures earlier than expected.”
In tackling a more precise life expectancy, in a project jointly initiated by the Austrian Society for Construction Technology (ÖBV), TU Graz and OTH Regensburg, researchers worked to define a more systematic understanding of shotcrete applications, leading them to form a new basis for more durable concrete mixes in tunnels.
According to the research findings, shotcrete can be designed more durable when cements, supplementary cementitious materials, admixtures and aggregates are better matched to the requirements. In the collaborated investigations, the team found that granulated blast furnace slag—in combination with other supplementary cementitious materials—is an effective way of increasing resistance against sulphate attack. These sulphate ions are traditionally observed as a result of gypsum dissolution and can be witnessed in soil or groundwater and lead to deformations and even cracks in the concrete.
Additionally, supplementary cementitious materials such as metakaolin or siderite can help to reduce the contribution of shotcrete to sinter formations (process of calcium carbonate precipitation) in the drainage system. These issues can further lead to the clogging of tunnel drainage systems, which can lead to tunnel closure for maintenance and repair.
The team also found that even the smallest addition of ultrafine limestone powder can significantly increase the early strength of shotcrete, making it possible to use the additives for more durable and sustainable shotcrete materials.
In October, engineers from RMIT University (Melbourne, Australia) announced that they had developed an eco-friendly, zero-cement concrete that could withstand corrosive acidic environments, commonly observed in sewage pipes and other types of wastewater infrastructure.
According to RMIT, the material consists of manufacturing by-products including a zero-cement composite of nano-silica, fly-ash, slag and hydrated lime. In using the industrial by-products, the end result is reported to surpass sewage strength standards set by ASTM International and is more durable than ordinary Portland cement.
“Though ordinary Portland cement is widely used in the fast-paced construction industry, it poses long term durability issues in some of its applications,” Roychand reported. “We found making concrete out of this composite blend—rather than cement—significantly improved longevity.”
Additionally, the final product is also environmentally friendly, reduces concrete corrosion by 96% and eliminates residual lime that is instrumental in the formation of fatbergs.
A paper on the study, "Development of zero cement composite for the protection of concrete sewage pipes from corrosion and fatbergs" has since been published in Resources, Conservation & Recycling.
And, most recently, researchers from Nagoya University discovered a rare concrete-strengthening mineral within the walls of a decommissioned power plant in Japan.
The mineral, aluminous tobermorite, is reported to have allowed Roman concrete marine barriers to survive for more than 2,000 years.
In Rome, the aluminous tobermorite formed because of seawater dissolving volcanic ash in the mixture, ultimately allowing the concrete marine barriers to endure conditions for over two millennia.
According to the university, because the mineral is a crystal, it makes concrete more chemically stable and stronger. However, the mineral is very difficult to incorporate directly into modern-day concrete materials.
In the case of the Hamaoka Nuclear Power Plant specifically, university researchers found that the aluminous tobermorite increased the strength of the walls more than three times their design strength.