Stronger sealed concrete with nanotechnology

Comparison of a concrete sample coated with nanomodified sealant (left) with untreated concrete (right). Credit: WSU

The penetrating sealant, developed using nanomaterials developed by researchers at the University of Washington, is better able to protect concrete from moisture and salt – the two most harmful factors that destroy concrete infrastructure in the northern states.

In laboratory studies, the new sealant showed a 75% improvement in water repellency and a 44% reduction in salt damage compared to a commercial sealant. Work could be an additional way to address the aging of bridges and sidewalks in the United States

“We focused on one of the main culprits, which violates the integrity and durability of concrete, namely moisture,” said Xianming Shi, a professor at the Department of Civil and Environmental Engineering who supervised the work. “If you can keep the concrete dry, the vast majority of strength issues will go away.”

Shi and graduate student Zhipeng Lee recently published their work in the Journal of Materials in Civil Engineering and applied for a preliminary patent.

Much of the country’s critical infrastructure, such as the U.S. Highway System, was built from the 1950s to the 1970s and is now coming to an end with the service life for which it was designed. Every four years since the late 1990s, the American Society of Civil Engineers provides a report on U.S. infrastructure showing consistently bad or bad grades. About 8% of the approximately 600,000 bridges in the U.S. are considered structurally deficient, and every fifth mile of sidewalk highway is in poor condition. The problem is exacerbated in cold climates due to numerous cycles of freezing and thawing, as well as due to the increased use of salts to combat the debate in recent decades that could worsen concrete.

“Concrete, even if it seems like a hard rock, is mostly a sponge when you look at it under a microscope,” Shea said. “It’s a very porous, heterogeneous composite material.”

Topical sealants have become one of the tools to protect concrete, and many public transportation departments use them, particularly to protect bridges that seem to suffer the most from salt damage. Sealants on the market provide a certain level of protection, but moisture can often seep into concrete, Shi said.

In their study, the researchers added two nanomaterials,[{” attribute=””>graphene oxide and montmorillonite nanoclay, to a commercial siliconate-based sealer. The nanomaterials densified the microstructure of the concrete, making it more difficult for liquid water to penetrate. They also formed a barrier against the intrusion of water vapor and other gasses that tend to make their way into the concrete. The nanomaterial also protected the concrete from the physical and chemical attacks of deicing salts. The penetrating sealer is designed to be multi-functional, as it can also serve as a curing aid for fresh concrete.

The WSU sealer is water-based instead of using any organic solvent, which means it’s more environmentally friendly and safer for workers, Shi added. 

“Traditionally, when you switch from an organic solvent to water, you sacrifice the sealer’s performance,” he said. “We demonstrated that the use of nanomaterials mitigates that reduction in performance.” 

The researchers have done preliminary market analysis with industry stakeholders and are studying ways to further optimize the sealers. They are investigating how the nanomaterials-based sealers might help protect concrete from microbial damage or abrasion, the daily wear and tear that damages the material in high-traffic areas. They plan to conduct pilot-scale demonstrations in the next two years, deploying an experiment of concrete infrastructure on the WSU campus or in the city of Pullman.  

Reference: “Effects of Nanomaterials on Engineering Performance of a Potassium Methyl Siliconate–Based Sealer for Cementitious Composite” by Zhipeng Li, S.M.ASCE and Xianming Shi, F.ASCE, 16 February 2022, Journal of Materials in Civil Engineering.
DOI: 10.1061/MT.1943-5533.0004148

The work was supported by the WSU-led National Center for Transportation Infrastructure Durability and Life-Extension and the WSU Office of Commercialization. Stronger sealed concrete with nanotechnology

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