Sand is one of the most important materials in construction. It is used to build everything from roads and bridges to harbors and skyscrapers.
Traditionally, river sand has been the go-to choice, but as collecting river sand becomes more restricted or even impossible in many places, builders have turned to sea sand as an alternative.
Sea sand, however, comes with a serious problem: salt.
If salt is not removed before the sand is used in concrete, it can cause the steel bars inside the concrete to rust. This corrosion weakens buildings and shortens their lifespan, putting safety at risk.
To prevent this, the Ministry of Land, Infrastructure and Transport in Korea requires that sea sand used in construction contain no more than 0.04% salt.
The problem is that removing salt is not easy. Right now, the standard way is to wash sea sand with huge amounts of fresh water—about four tons of water for every ton of sand. This is not only wasteful but also slow and expensive.
Researchers at the Korea Institute of Ocean Science & Technology (KIOST) have now come up with a much more efficient method.
Led by Dr. Gil-Lim Yoon, the team developed an ultrasonic washing device that uses sound waves to remove salt from sea sand.
The technique relies on cavitation, which means tiny bubbles form and collapse violently when exposed to ultrasonic waves. This creates a strong cleaning effect, shaking loose the salt that clings to the sand grains.
The process is surprisingly fast and efficient. Instead of dumping tons of water on the sand, the new method mixes sea sand with water at a simple 1:2 ratio and then blasts it with ultrasonic waves of 300 watts or more for just three minutes.
This is enough to bring the salt level down to the safe standard of 0.04% or less. It also works well even in tight or confined spaces, using less water and far less time than the old method.
KIOST President Hyi Seung Lee says this breakthrough is important not only for South Korea but also for the world. As river sand becomes scarcer, safe and efficient use of sea sand will be vital for future infrastructure.
The team hopes to further improve the technology so it can be used on a large scale, ensuring strong, durable, and cost-effective construction.
