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| Photo credit: Washington University |
Researchers at Washington University (WU) have developed a nano-engineered sealer that can prevent concrete from damage. The sealer protects concrete from deteriorating after exposure to salt and water.
In laboratory studies, the sealer showed a 44 percent improvement against the damage due to salt and a 77 percent increment in water-repelling abilities. This study suggests new approaches to deal with infrastructure problems in the U.S.
“We focused on one of the main culprits that compromise the integrity and durability of concrete, which is moisture,” said Xianming Shi, study lead author and WU professor. “If you can keep concrete dry, the vast majority of durability problems would go away.”
Most of the infrastructure in the U.S. was developed in the mid 20th century and now is at the end of its lifetime. Since the late 1990s, the American Society of Civil Engineers has released reports on the U.S. infrastructure every four years and has consistently shown falling grades.
About eight percent of 6,00,000 bridges in the U.S. have a structural deficiency. Also, one out of every five miles of highways is in bad condition. These problems increase in the cold areas as the use of deicer salt to melt ice on roads degrades the quality of concrete. All these issues indicate an urgent requirement for development in the infrastructure sector.
“Concrete, even though it seems like solid rock, is basically a sponge when you look at it under a microscope,” said Shi. “It’s a highly porous, non-homogenous composite material.”
Topical sealers are one such tool to protect concrete. These sealers sit on the material’s top and don’t allow molecules to penetrate inside them. Thus, many transportation agencies use them to prevent bridges and decks from being damaged. Though these sealers provide some extent of protection, they don’t provide complete safety against moisture, added Shi.
A new nanomaterial mix
To make the nano-sealer, researchers added two construction-based nanomaterials, montmorillonite nano clay and graphene oxide to a commercial silicone-based sealer. Graphene oxide is a graphite compound used to increase longevity in construction materials. On the other hand, montmorillonite is a naturally occurring clay used to bind concrete molecules and harden the structure.
These nanomaterials increased the density of the concrete molecular structure that blocked water from penetrating. They also formed a barrier to block water vapour and other gases from entering the concrete layer.
The nanomaterials were also found to prevent concrete from physical and chemical attacks of deicing salt. The penetrating sealer provides multi-functional support to concrete and increases its life. Moreover, researchers didn’t use any organic solvent to form the sealer. It is water-based, hence it’s more environment friendly and safer for workers.
“Traditionally, when you switch from an organic solvent to water, you sacrifice the sealer’s performance,” said Shi. “We demonstrated that the use of nanomaterials mitigates that reduction in performance.”
Further, researchers have done a primary analysis of the construction market with industry experts to make more improvements in sealers. They are working on finding how nano-sealers can protect concrete from microbial attacks or abrasion, daily damages due to high traffic, etc. Further research can help to craft long-lasting concrete that can withstand extreme conditions.
The research was published in the Journal of Materials in Civil Engineering.
Contributed by: Simran Dolwani
