Bentonite slurry is a common type of soil stabilizing liquids. Bentonite used to stabilize the soil for deep foundations such as cast-in-situ piles during the drilling stage. Also, it is commonly used for stabilizing the drilled soil for the diaphragm wall. The bentonite powder is mixed with water. Then it is poured during the drilling of a pile hole to stabilize the soil and prevent the soil from collapse. Bentonite is used where the soil is weak and it is expected to collapse during the drilling of piles or other types of excavations. The bentonite will provide sufficient time to lower the steel reinforcement and cast the concrete while the soil is stable.
The mixing of water with bentonite will produce gell products when left to stand for sometimes. This product will return quickly to the liquid state when it is in motion. Bentonite mixture should be tested for viscosity, sand content, ph, and density. The test results should be within the permissible values as per the project specifications. The density of bentonite can significantly affect bentonite performance. The increase of bentonite density will result in improving the bores or excavation stability. Also, it will keep the particles in suspension, and it will reduce the flow of bentonite to soil with high permeability such as sandy soil. However, it is preferable to use bentonite with low density. Bentonite with low density can be displaced efficiently from the excavation or bores. Furthermore, the pumping of low-density bentonite is easier. The bentonite stabilizing the soils of bores or excavation by the following mechanism. The bentonite slurry will penetrate the soil and leave a layer of bentonite on the surface of the soil. The bentonite particles will form a filter cake on the surface of excavation when the pressure of the bentonite mixture is higher than the pressure of pore water in excavated soil. The filter layer will work as an impermeable layer, and it will allow the bentonite slurry to exert full hydrostatic pressure on excavated soil walls surface. For pile works, we should ensure that bentonite doesn’t coat the steel cage and impair the bond between reinforcement and concrete. Also, it should be displaced easily from the pile holes. Moreover, we should ensure that the bentonite doesn’t affect the environment.