4.1 This practice provides a systematic procedure for sampling and determining the variability of user-selected properties of concrete-making materials. Results derived from application of the practice are generally intended for information only and are not requirements of any existing ASTM specification on concrete or concrete-making materials. A concrete materials specification may make reference to this practice as a means of obtaining variability information, but needs to define the properties to be measured and the lot size and sample unit to be used. This practice is applicable to both producers and consumers of concrete-making materials, although details of application of the practice may vary, depending on the intended purpose of the user of this practice.

4.2 The procedure is applicable to any quantitative property of any concrete-making material that can be measured by a standard test method. The procedure is based on grab samples, which will tend to show the maximum amount of variation of the material being evaluated. The procedure is useful if grab samples are obtained from sampling units that are being delivered to the user of a material and better represents the variability of the material used in concrete production than tests performed on the material for specification compliance that are documented on a mill test report or material certification. The procedure was developed for application to materials from a single source, but it can be applied to a materials delivery stream from more than one source, depending on the purposes of the user of the practice. Variations among test results on separate samples within a lot are corrected for testing error, therefore giving an estimate of the variability of the selected material property. The variability of the selected material property provides the user with one indicator of the source variation of the concrete-making material.

4.3 Although variability in properties of concrete-making materials can be a significant cause of variability in concrete properties, this practice does not purport to give information on this relationship. This practice does give information on variability of concrete-making materials from which the user can, along with supplementary information or correlative testing of concrete properties, develop quantitative estimates of the effects.