of water so as to obtain the lowest density fig1 and 3 show the theological curves of slurries 2 according to various temperature conditions and compositions x and y these rheological curves show that these compositions have too high rheologies for a cement slurry notably for low shears it can be noted that the addition of an amount of hb1 to the formulation of slurry 2 allows to obtain an acceptable rheology for a cement slurry the use of hb1 allows to optimize the rheology of the mixture and thus to meet the requirements the optimum properties are obtained with about 3 hb 1 compressive strength bar of slurry 2 without disal x 0 comparatively a conventional mixture based on class g cement and microsilica with a high water content e c 0 94 has under the same conditions a compressive strength of 65 bars a filtered volume of 25 ml in 30 minutes but above all a free water volume of 1 5 which indicates a high sedimentation risk also a mixture of class g cement and of bentonite with a high water content e c 0 94 has a low compressive strength of the order of 30 bars measured under the same conditions this slurry contains a higher proportion of water and no dispersant however it does not sediment because of the nature of the particles but the cement once hardened has a compressive strength of 42 bars after 2 days at 20 u00b0 c which is relatively low this mixture decants almost immediately the disal type dispersant is incompatible with such a formulation these various tests thus show.