Bentonite, a mineral clay with unique properties, is vital in strengthening civil engineering structures. This material is widely used in civil engineering projects such as foundation construction, dams, tunnels, retaining walls, and drainage systems. Thanks to its ability to fill voids, reduce soil permeability, and enhance structural stability, bentonite helps engineers manage challenges related to unstable soils, water seepage, and hydraulic pressure. These characteristics are especially critical in areas with loose soil or complex hydrogeological conditions, making bentonite an essential component in infrastructure projects that not only improve structural integrity but also increase the lifespan of constructions.
One of the primary functions of bentonite in strengthening civil structures is its use as a sealing material in foundations and retaining walls. In projects involving deep foundations or piles, bentonite is injected as a slurry—a mixture of bentonite powder and water—to create an impermeable layer around the structure. This slurry fills cracks and voids in the soil, preventing water infiltration into the foundation while also contributing to the stability of the surrounding soil. For instance, in the diaphragm wall method, bentonite slurry is poured into excavated trenches to support the walls against collapse and, after concrete placement, forms a permanent waterproof barrier. This property not only protects the structure from groundwater pressure but also reduces the risk of soil erosion and uneven settlement, both of which can lead to structural failure.
In the construction of dams and hydraulic structures, bentonite acts as a natural sealing layer that helps improve the stability of these systems. Earth or rockfill dams built to store water or control flooding often face the challenge of water leakage through the body or foundation. In such cases, bentonite is applied either as powder or in geosynthetic sheets within the dam’s internal layers. Upon contact with water, bentonite swells and forms an impermeable barrier that prevents seepage. This feature is particularly important for dams constructed on sandy or highly permeable soils. Furthermore, by increasing soil particle cohesion, bentonite enhances the shear strength of the soil, thereby contributing to the overall structural strength—an essential factor for resistance against hydraulic forces and earthquakes.
Another significant application of bentonite in structural reinforcement is in tunneling and underground projects. In shield tunneling or slurry injection methods, bentonite acts as both a lubricant and a stabilizer. When injected into tunnel walls, the bentonite slurry balances earth and water pressure, preventing wall collapse. It also forms a protective layer that stops water from entering the tunnel and prevents the excavation material from escaping. In metro projects, water or sewage transfer tunnels, this property of bentonite increases structural resilience against geological and hydraulic pressures and reduces long-term maintenance costs. Additionally, since bentonite is a natural, non-toxic material, its use aligns with environmental standards and has fewer harmful effects compared to synthetic chemical alternatives.
Finally, bentonite contributes to the reinforcement of infrastructure such as roads, bridges, and airport runways by improving the mechanical properties of weak soils. In soils with low bearing capacity or those prone to swelling and shrinking (like clayey soils), adding bentonite can enhance cohesion and stability. This is achieved either by mixing bentonite with native soil or applying it in layers to prevent structural deformation under heavy loads. For example, in airport runway construction—which must support the weight of aircraft—bentonite can help stabilize the underlying soil and prevent settlement or cracking. Overall, with its combination of physical and chemical properties—such as swelling capacity, sealing ability, and stabilizing effect—bentonite is a multifunctional material in civil engineering that contributes to structural reinforcement, cost reduction, and improved safety and durability.
written by: Sara Ebrahimi
