A nanomaterials-engineered penetrating sealer developed by Washington State University researchers can better protect concrete from moisture and salt – the two most damaging factors in crumbling concrete infrastructure in northern states.
In laboratory tests, the novel sealer demonstrated a 75% increase in water repellency and a 44% decrease in salt damage compared with a commercial sealer. This work could be an additional solution to the problem of old bridges and pavements in America.
Professor Xianming Shi of the Department of Civil and Environmental Engineering, who was the research leader, said, “we focused on one of these main culprits that compromise concrete’s integrity and durability, which is moisture.” Concrete durability problems can be eliminated if the concrete is kept dry.
Shi and Zhipeng Li, a graduate student, recently published their work in the Journal of Materials in Civil Engineering. They have also applied for a provisional Patent.
Many of America’s most important infrastructures, including the U.S. highway network, were built between the 1950s and the 1970s. They are now at the end of their design life. The American Society of Civil Engineers provides a report card annually on U.S. infrastructure. About 8% of the approximately 600,000 bridges in America are structurally deficient. One out of five miles of highway pavement is in poor condition. Cold climates worsen the problem, as multiple freeze-thaw cycles and increased use of salts (deicer salts) can cause concrete to deteriorate.
Shi stated that concrete, even though it looks like solid rock, actually acts as a sponge under a microscope. It’s a composite material that is highly porous and non-homogenous.
One tool for protecting concrete is the topical sealer. Many state transportation departments use them to protect bridge decks most vulnerable to salt damage. Shi stated that although the sealers protect concrete, moisture can still penetrate the concrete.
The researchers used graphene oxide and montmorillonite as nanomaterials in their research. They also added a silicone-based sealer. The nanomaterials densified the concrete’s microstructure, making liquid water more difficult to penetrate. They also prevented water vapour and other gases from entering the concrete. The concrete was also protected from chemical and physical attacks by deicing salts due to the nanomaterial. This penetrating sealer can be used to cure concrete as well as as a protective layer.
She said that WSU sealers are water-based and do not contain any organic solvents. This makes them more sustainable and safer for workers.
He stated that switching from an organic solvent to water can lead to a loss of sealer performance. “We have shown that nanomaterials can reduce that loss in performance.”
Researchers have conducted a preliminary market analysis with stakeholders in the industry and are now looking at ways to optimize the sealers. The researchers are currently investigating how nanomaterial-based sealers could protect concrete against microbial damage and abrasion. This is due to the daily wear that causes concrete to crack in high-traffic areas. In the next two years, they plan to do pilot-scale demonstrations using a concrete infrastructure experiment on the WSU campus and in Pullman.