【国外标准】 Standard Guide for Comparing Performance of Concrete-Making Materials Using Mortar Mixtures

4.1 The results of mortar mixture tests can be suitable for comparing the relative performance of combinations of concrete-making materials such as fine aggregate, chemical admixtures, supplementary cementitious materials (SCMs), water, and hydraulic cement. Furthermore, this guide can be useful to identify unexpected performances due to combination of various materials. The relative trends in performance observed with the mortar method may suggest relative performance in concrete mixtures batched with the same materials and relative mixture proportions.4.2 While there are a number of ways to proportion and mix mortar mixtures, four procedures described in this guide have been used extensively for evaluating the performance of admixtures. Method A enables evaluation of materials using mixture proportions that correspond to specific job conditions. Method B can be used as a general mixture using fixed amounts of a standard sand, cement, and supplementary cementitious materials. Method C is a modified version of Test Method C359 to evaluate the impact of chemical admixtures on the early stiffening of a mortar prepared with specified amounts of job cement, a standard sand, and an amount of water that will produce a mortar with a specified initial penetration measured in accordance with Test Method C359. The measurements of penetration over time can be related to the early stiffening processes associated with false and flash set. Method D is a modified version of Test Method C185 whereby the mortar mixture can be prepared with various combinations of chemical admixtures, supplementary cementitious materials, and job water. Methods A and B would be most applicable for investigating material incompatibility issues associated with ready mixed concrete, while Method C would be applicable for concrete mixed for a short period of time in stationary mixers and transported to the forms in non-agitating equipment. Method D is suitable for all concrete mixing processes and is most applicable if the focus of a material incompatibility issue is unexpected changes in air content.1.1 This guide provides information on how to compare the relative performance and potential incompatibility of combinations of concrete-making materials. Performance tests on fresh and early-age properties of mortar mixtures can be useful indicators of concrete performance using similar materials. The performance tests described in this guide include mortar-slump, mortar spread, mortar-workability retention, early stiffening of mortar, time of setting, air entrainment, and hydration kinetics.1.2 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with this guide. Some values only have SI units because the inch-pound equivalents are not used in guide.1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Warning—Fresh hydraulic cementitious mixtures are caustic and may cause burns to skin and tissue upon prolonged exposure.21.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.