EPFL researchers have developed a technique to stabilize poorly permeable soils. They use an electric current applied through electrodes planted in the ground, like a giant battery.
The Soil Mechanics Laboratory of the Swiss Federal Institute of Technology in Lausanne (EPFL) has already developed several sustainable stabilization processes, in particular through the metabolism of enzymes. Effective for many terrains, they are not sufficient for clay soils.
In a new study published in the journal Scientific Reports, researchers show how chemical reactions can be improved by an electric current generated like an electric battery.
In recent years, a biocement produced on site and at room temperature seems promising for the stabilization of many types of soil. The method consists in durably binding the particles by calcite crystals by taking advantage of the metabolism of bacteria.
Not very energy-intensive and inexpensive, it is ready to be deployed quickly over the next few years. But this bio-geo-chemical process requires the impregnation of the ground. For the moment, it is therefore hardly compatible with clayey soils with low permeability.
Wishing to have a viable alternative, EPFL scientists successfully tested the effect of an electric current applied through electrodes planted in the ground.
Like a giant stack
“The results show the capacity of the geo-electro-chemical system to influence the evolution of calcification and especially the key phases of crystal formation and enlargement, these bonds which improve the behavior of soils”, notes Dimitrios Terzis, co-author of the article, quoted Tuesday in a press release from the Lausanne university.
In the process leading to the biocement, dissolved carbonate and calcium ions come into play. They carry an opposite charge. By creating an electric field with anodes and cathodes inserted in the ground, much like a giant battery, these ions are forced to pass through low permeability media. They intersect, mix and eventually cause the expected reaction.
The result is the growth of carbonate minerals which act as bonds or “bridges” to improve the mechanical performance and strength of soils.
Observation and measurement of the quality of these mineral bridges are at the heart of this publication which lays the foundations for this field of study, according to EPFL. Further testing at various scales will still need to be performed before actual use.
Until recently, soils were viewed as a mixture of solid earth, air, and water. “This work highlights the potential that lies in interdisciplinarity by introducing notions of biology and electrochemistry. New and exciting avenues are opening up by integrating advances and mechanisms from other fields of science”, emphasize the researchers. co-authors.