1.1 本试验方法描述了显微测定硬化混凝土空气含量和硬化混凝土中空隙系统的比表面积、空隙频率、间距系数和膏体空气比的程序。描述了三个程序: 1.1.1 程序A-- 线性导线法。 1.1.2 程序B-- 修改了点计数方法。 1.1.3 程序C-- 对比增强法。 1.2 本试验方法基于适用于现场或实验室混凝土试样锯切和搭接部分的规定程序。 1.3 其目的是概述本试验方法的原理，并为其足够的性能制定标准，但不详细描述可能用于实现本试验方法目标的所有可能变化。 1.4 以国际单位制或英寸-磅单位表示的值应单独视为标准值。每个系统中所述的值不一定是完全等效的；因此，为确保符合标准，每个系统应独立使用，两个系统的值不得组合。 1.5 本标准并不旨在解决与其使用相关的所有安全问题（如果有的话）。本标准的使用者有责任在使用前建立适当的安全、健康和环境实践，并确定监管限制的适用性。 关于具体的危害声明，请参见 附注9 和 附注12 . 1.6 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 =====意义和用途====== 5.1 通过本试验方法中描述的程序确定的硬化混凝土空隙系统的参数与混凝土水泥浆部分对冻融损伤的敏感性有关。因此，该测试方法可用于开发数据，以估计循环冻融造成的损坏可能性，或解释其发生的原因。该试验方法也可用作开发产品或程序的辅助手段，以提高混凝土对循环冻融的抵抗力。 5.2 空隙系统的参数值可以通过本试验方法中描述的任何程序获得。 选择使用三种方法中的哪一种应得到用户和确定提供者的同意 注1: 由于程序C要求使糊状物和骨料变暗，如果分析员除了本试验方法中描述的测量外还收集岩相数据，则必须在其他试验后使用。 5.3 没有规定区分夹杂的空气空隙、夹带的空气空隙和水空隙。任何这样的区分都是任意的，因为各种类型的空隙在大小、形状和其他特征上是相互融合的。做出这种区分的报告通常将截留的空气空隙定义为至少在一个维度上大于1mm，形状不规则，或两者兼而有之。 由于混凝土未能正确压实而导致的蜂窝状结构是一种夹杂的空隙。 5.4 水洞是混凝土凝固时充满水的空腔。它们仅在含有过量混合水或发生明显出血和沉降的混合物中具有重要意义。它们最常见于水平钢筋、粗骨料块下方，以及沿其侧面的通道。它们也发生在泌水完成前通过精加工操作压实的表面下方。 5.5 当混凝土包含标称最大粒径较大的骨料，如50 mm[2 in。 ]或更多。此类混凝土的制备部分应包括最大的砂浆分数，以增加空隙或穿过空隙的计数。必须准确知道或估计原始混合物中骨料体积与浆料体积的比率，以便根据显微镜下确定的浆料空气比计算空隙系统参数。 注2: 根据本试验方法测定的空隙率通常与根据试验方法在新浇混凝土上测定的值非常接近 C138/C138米 , C173/C173M ，或 C231/C231米 然而，如果新浇混凝土样品的固结程度与后来显微镜检查的样品不同，则可能会观察到显著差异。 对于空气含量相对较高（通常超过7.5%）的混凝土，显微镜下测定的值可能比试验方法测定的值高一个或多个百分点 C231/C231米 .

1.1 This test method describes procedures for microscopical determinations of the air content of hardened concrete and of the specific surface, void frequency, spacing factor, and paste-air ratio of the air-void system in hardened concrete. Three procedures are described: 1.1.1 Procedure A— Linear-traverse method. 1.1.2 Procedure B— Modified point-count method. 1.1.3 Procedure C— Contrast enhanced method. 1.2 This test method is based on prescribed procedures that are applied to sawed and lapped sections of specimens of concrete from the field or laboratory. 1.3 It is intended to outline the principles of this test method and to establish standards for its adequate performance but not to describe in detail all the possible variations that might be used to accomplish the objectives of this test method. 1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined. 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements see Note 9 and Note 12 . 1.6 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. ====== Significance And Use ====== 5.1 The parameters of the air-void system of hardened concrete determined by the procedures described in this test method are related to the susceptibility of the cement paste portion of the concrete to damage by freezing and thawing. Hence, this test method can be used to develop data to estimate the likelihood of damage due to cyclic freezing and thawing or to explain why it has occurred. The test method can also be used as an adjunct to the development of products or procedures intended to enhance the resistance of concrete to cyclic freezing and thawing. 5.2 Values for parameters of the air-void system can be obtained by any of the procedures described in this test method. The selection of which one of the three methods to be used shall be subject to agreement of the user and provider of the determination Note 1: Because Procedure C requires darkening the paste and aggregate, its use must occur after other tests if the analyst is also gathering petrographic data in addition to the measurements described in this test method. 5.3 No provision is made for distinguishing among entrapped air voids, entrained air voids, and water voids. Any such distinction is arbitrary, because the various types of voids intergrade in size, shape, and other characteristics. Reports that do make such a distinction typically define entrapped air voids as being larger than 1 mm in at least one dimension being irregular in shape, or both. The honey-combing that is a consequence of the failure to compact the concrete properly is one type of entrapped air void. 5.4 Water voids are cavities that were filled with water at the time of setting of the concrete. They are significant only in mixtures that contained excessive mixing water or in which pronounced bleeding and settlement occurred. They are most common beneath horizontal reinforcing bars, pieces of coarse aggregate and as channelways along their sides. They occur also immediately below surfaces that were compacted by finishing operations before the completion of bleeding. 5.5 Application of the paste-air ratio procedure is necessary when the concrete includes large nominal maximum size aggregate, such as 50 mm [2 in.] or more. Prepared sections of such concrete should include a maximum of the mortar fraction, so as to increase the number of counts on air voids or traverse across them. The ratio of the volume of aggregate to the volume of paste in the original mix must be accurately known or estimated to permit the calculation of the air-void systems parameters from the microscopically determined paste-air ratio. Note 2: The air-void content determined in accordance with this test method usually agrees closely with the value determined on the fresh concrete in accordance with Test Methods C138/C138M , C173/C173M , or C231/C231M . However, significant differences may be observed if the sample of fresh concrete is consolidated to a different degree than the specimen later examined microscopically. For concrete with a relatively high air content (usually over 7.5 %), the value determined microscopically may be higher by one or more percentage points than that determined by Test Method C231/C231M .