Removing sand to create rock can help curb coastal erosion

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But sending low-voltage electricity through waterlogged sands can stimulate the formation of minerals that help bind sediments together, Rotta Loria and colleagues report online Aug. 22 in Earth and Environment Communications. The mineral components are already dissolved in the seawater, the researchers point out.

Sending just 4 volts through a mixture of sand and seawater for 28 days caused mineralization. Using a rod-like electrode with a diameter of 2 centimeters can create a rock pipe up to 80 centimeters wide. Calcium carbonate and magnesium hydroxide were the most common minerals. “It’s basically limestone,” says Rotta Loria.

  1. This illustration shows a grid of blue lines in the water along the coastline on which houses rest on the sandy cliffs above. The blue color illustrates the use of low-voltage electricity to turn sand into stone and protect the coast from erosion.
    Minerals created when low voltages are passed through seawater-soaked sand can help strengthen shorelines and slow erosion, as this illustration suggests. Northwestern University
  2. Blue bubbly material fills the middle and top of this microscope image. It shows the minerals created when sand is blasted with low-voltage electricity in an attempt to sand into stone.
    This microscopic image shows how sand solidifies into rock. The blue area is the minerals created when low voltages help precipitate minerals dissolved in seawater. Northwestern University
  3. Two pieces of rock sit on top of a pile of sand. The rocks were created by breaking down water-saturated sand with low-voltage electricity.
    These rock samples were created by passing low-voltage electricity through water-soaked sand. Northwestern University

Strength tests revealed that the newly formed rock was about one-tenth as strong as concrete. But even this can help the coasts resist erosion. The mineralization process can help strengthen the sandy areas at the base of the cliffs, thus slowing erosion that would cut the rocks and slow their retreat from the coast. Or it can be used to strengthen foundations under shoreline homes, either on slabs or piles. It could also be used to “heal” some cracks in existing concrete structures, the researchers suggest.

The mineralization method is eco-friendly—the voltages are too low to be felt by marine life—and it should also be economical, notes Rotta Loria. The process is likely to cost between $3-$6 to harden a cubic meter of seawater-soaked sand, the team estimates. Trucking in sand can cost roughly $14-$30 per cubic meter, taking billions to replenish a beach.


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Image Source : www.sciencenews.org

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