ASTM C1698-09(2014)
水泥浆和水泥砂浆自应力的标准试验方法
Standard Test Method for Autogenous Strain of Cement Paste and Mortar
- 标准号
- ASTM C1698-09(2014)
- 发布
- 2009年
- 发布单位
- 美国材料与试验协会
- 替代标准
- ASTM C1698-19
- 当前最新
- ASTM C1698-19
- 引用标准
- ASTM C1005 ASTM C125 ASTM C157/C157M ASTM C191 ASTM C192/C192M ASTM C219 ASTM C305 ASTM C403/C403M
- 适用范围
5.1 Autogenous strain is the self-created bulk strain of cement paste, mortar, or concrete during hardening at constant temperature. In conventional concrete, autogenous shrinkage strain is generally negligible, but in concrete with low water-cementitious materials ratio (w/cm) or with silica fume it may be considerable (1).5 Restraint of the autogenous strain by aggregates or adjoining structural members may result in formation of micro and macro cracks that impair strength, durability and aesthetics. Cracks may also be a problem with regard to hygienic cleaning of surfaces.
5.2 An accurate measurement of the autogenous strain of cementitious mixtures with low w/cm is important for evaluating the risk of early-age cracking of concrete structures. Measurements of autogenous strain have been carried out using either volumetric or linear methods. Both methods may show evidence of significant artifacts (1); therefore, results of the two methods may disagree considerably if not carried out properly.
5.3 A sealed, flexible corrugated mold system (2) combines the advantages of linear and volumetric measurement of autogenous strain, while avoiding most of their disadvantages. The mold effectively prevents moisture loss and minimizes restraint to volume change during hardening. Moreover, results obtained with the corrugated mold system agree with those from the volumetric method, once some artifacts, in particular water absorption through the membrane used to contain the test specimen, have been eliminated in the latter (3,4). The corrugated mold system is easier to use and shows better repeatability than the volumetric technique (3,4). Measurements with the corrugated mold system are in good agreement with unrestrained length change measurements obtained using Test Method C157/C157M with sealed specimens (5); however, Test Method C157/C157M does not allow measurement of the shrinkage occurring before 24 h (5).
5.4 This test method can be used to evaluate the effects of cementitious materials, admixtures, and mixture proportions on autogenous shrinkage strain of paste or mortar specimens.
5.5 The autogenous shrinkage strain of mortar specimens will be less than that of paste specimens for the same 水泥砂浆流变仪构造组成部分
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