Hydraulic Conductivity of Bentonite Grouted Sand

The yield stress and viscosity of bentonite suspensions treated with Sodium Pyrophosphate (SPP) were measured to investigate the applicability of modified bentonite suspensions as a permeation grout. The yield stress and viscosity were significantly reduced with the addition of Sodium Pyrophosphate (SPP). The main advantage of using SPP is the temporary nature of the reduction in yield stress and viscosity; both parameters increase with time and exceed the values of the original suspension without the SPP. Permeability tests were conducted to verify the effectiveness of the bentonite suspensions in decreasing the hydraulic conductivity of the sand. Permeated samples were prepared with clean sand and bentonite using 7.5, 10, and 12% bentonite suspensions. The results showed that hydraulic conductivities of the sand decreased by 4, 4.5 and 5 orders of magnitude with grout bentonite contents of 7.5%, 10% and 12%, respectively. These findings suggest the possible application of Sodium Pyrophosphate (SPP) treated bentonite suspensions in permeation grouting for controlling hydraulic conductivity.