1.1 本试验方法提供了确定结构轻质混凝土的烘干密度和平衡密度的程序。 1.2 以国际单位制或英寸-磅单位表示的数值应单独视为标准值。每个系统中规定的值可能不是精确的等效值；因此，每个系统应相互独立使用。将两个系统的值合并可能会导致不符合标准。有些值只有国际单位制，因为在实践中没有使用英寸-磅当量。 1.3 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）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》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 结构轻质混凝土的测量或计算平衡密度决定是否满足规定的密度要求。除非另有规定，否则使用中的程序通过计算确定平衡密度 9.2 . 5.2 试验方法 C138/C138M 应用于确定新拌轻质混凝土的密度，以符合混凝土浇筑规范。 注1: 轻骨料混凝土的新鲜密度是混合比、含气量、需水量以及轻骨料的比密度和含水量的函数。特定轻质混凝土密度的降低是由于水分损失，而水分损失又是骨料含水量、环境条件和混凝土构件表面积与体积比的函数。对于大多数结构轻质混凝土，在大约90天时接近平衡密度。对于大多数高强度轻质混凝土，在大约180天时接近平衡密度。大量试验表明，尽管轻集料的初始含水量有所变化，但平衡密度约为50 kg/m 3. [3.0磅/英尺 3. ]大于烘箱干密度。

1.1 This test method provides procedures to determine the oven-dry and equilibrium densities of structural lightweight concrete. 1.2 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 the standard. Some values have only SI units because the inch-pound equivalents are not used in practice. 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. 1.4 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. ====== Significance And Use ====== 5.1 The measured or calculated equilibrium density of structural lightweight concrete determines whether specified density requirements have been met. Unless otherwise specified, determine equilibrium density by calculation using the procedures in 9.2 . 5.2 Test Method C138/C138M shall be used to determine the density of freshly mixed lightweight concrete for compliance with concrete placement specifications. Note 1: The fresh density of lightweight aggregate concrete is a function of mixture proportions, air content, water demand, and the specific density and moisture content of the lightweight aggregate. Decrease in density of a specific lightweight concrete is due to moisture loss that, in turn, is a function of aggregate moisture content, ambient conditions, and the ratio of the surface area to the volume of the concrete member. For most structural lightweight concretes, equilibrium density is approached at about 90 days. For most high-strength lightweight concretes, equilibrium density is approached at about 180 days. Extensive tests demonstrate that despite variations in the initial moisture content of lightweight aggregate, the equilibrium density will be approximately 50 kg/m 3 [3.0 lb/ft 3 ] greater than the oven-dry density.