This procedure facilitates the comparison of different types or grades of asbestos based on their contribution to the flexural modulus of rupture; that is, the reinforcing value, which is considered the most pertinent property for the manufacture of asbestos-cement products.

This test method is primarily intended for fiber grades used normally in asbestos-cement products (Group 6 to Group 4 fibers). Longer fibers (Group 3) or shorter fibers (Group 7) may present difficulties during the preparation of the filter cake because of poor dispersion and uneven settling.

1.1 This test method covers the measurement, on a laboratory scale, of the contribution of asbestos fibers to the strength of asbestos-cement products. The results obtained are used in the primary assessment of different fiber grades prior to their application on a larger scale.

1.2 This test method covers the determination of the modulus of rupture (MR), adjusted to a dry density of 1.60 Mg/m³ (MR _A), of asbestos-cement test specimens that contain the asbestos fiber to be evaluated at a concentration of 10 mass %, whereby the degree of fiberization of that fiber is specified in terms of specific surface area as determined by Test Method D2752. The relative reinforcing value of the fiber under test is established by comparison with MR_A values obtained with a fiber of known characteristics at a fiber concentration of 10 % and a dry density of 1.60 Mg/m³ (1.60 g/cm³).

Note 1—The adjusted modulus of rupture (MR_A) at any intermediate fiber concentration may be interpolated from results suitably determined over a limited spanning range of fiber concentrations. For example, the MR_A at 10 % fiber concentration may be graphically determined from data at 3 and 17 %.

1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.4 Warning—Breathing of asbestos dust is hazardous. Asbestos and asbestos products present demonstrated health risks for users and for those with whom they come into contact. In addition to other precautions, when working with asbestos-cement products, minimize the dust that results. For information on the safe use of chrysotile asbestos, refer to “Safe Use of Chrysotile: A Manual on Preventive and Control Measures.”

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.