ASTM C773-88 (2020) pdf free.Standard Test Method for Compressive (Crushing) Strength of Fired Whiteware Materials.
1.1 ASTM C773 pdf download.The test specimens shall be right cylinders. They may be formed and matured for the purpose of compression testing, or they may be cut from matured whiteware by sawing or coredilling. The ends of all specimens shall be ground or lapped to yield plane and parallel faces. These faces shall be perpendicular to the axis of the specimen, and parallel within 15 min of arc (0.044 rad).
1.2 Size- -The size of the specimen should be no larger than  to require more than 80 % of the rated capacity of the testing machine. Examples of specimen size limitations are shown in Table 2.
1.3 Number of Specimen —The number of specimens shall not be less than ten.
2.1 Dye-check specimens and contact cylinders in accor dance with Practice E165/E165M before testing. Discard any parts exhibiting cracks or faws visible to the unaided eye.
2.2 Center the specimen carefully in the machine between the bearing plates (Fig. 1) to avoid eccentric loading. Place an appropriate guard around the specimen to contain flying fragments at failure; eye protection should be used by the operator.
2.3 Apply the load continuously and without impact shock at a rate of 10 000 lbf/min (45 kN/min), within 20 %. Use only the load on the specimen at ultimate failure for calculation of the compressive strength.
3.1 Testing Machine- Any testing machine conforming to Practices E4 and to the requirements for speed of testing prescribed in Sections 5 and 12 of this test method, may be used.
3.2 Spherical Bearing Block—In vertical testing machines,the spherical bearing block shall be spring suspended from the upper head of the machine in such a manner that the upper platen of the machine (lower face of the spherical bearing block) remains in a central position (spherical surfaces in full contact) when not loaded. The spherical surfaces shall be well lubricated, and the center of curvature shall lie on the lower face of the platen. The diagonal or diameter of the platen shall be only slightly greater than the diagonal of the 1/-in. (38.1 mm) square contact blocks to facilitate accurate centering of the specimens.ASTM C773 pdf download.