This European Standard specifies a method based on water absorption with vacuum for the determination of the bulk density of granular refractory materials (grain bulk density) having a grain size greater than 2 mm. NOTE 1 This method is proposed as an alternative to the method based on mercury displacement with vacuum described in EN 993-17 which is to be used as the reference method because of its reproducibility. However, mercury is known to be a hazardous substance and the method described in this European Standard is recommended for all routine purposes. Nevertheless, depending on the nature of the material tested, the two methods may give different results. NOTE 2 For materials that are sensitive to contact with water, a suitable organic liquid should be used. The immersion liquid should not fractionate at a pressure above the absolute pressure attained in the test. For example, distilled paraffin can be used for hydratable materials.