The unusual behavior of a Milos bentonite in cement suspensions

Bentonites from different deposits worldwide often show unexplainable differences with respect to their performance in different applications. Examples are the water uptake capacity and bleaching ability (Kaufhold, 2001 and Kaufhold et al., 2010). The present study focused on the rheological parameters of bentonite-cement slurries used in civil and underground engineering. By measuring the viscosity and yield point of several different Na+-activated calcium bentonites mixed with blast furnace cement, behavior of a Milos bentonite was detected characterized by an unusual increase of the viscosity after addition of the cement. A detailed mineralogical characterization was conducted to identify the reason. The most striking difference of the samples was the content of soluble silica making up 27 mass% of the bentonite (soluble in hot sodium carbonate solution). However, the addition of silica gel to bentonites free of soluble silica proved the effect on the rheological parameters viscosity and yield point.

► The optimum activation cannot avoid the loss of viscosity after adding cement.
► Milos, Bavarian and Sardinian bentonites can be used in bentonite-cement slurries.
► The anomaly of a Milos bentonite was related to the high content of soluble silica.