Designation: c 157/C 157M – 08 Standard Test Method for Length Change of Hardened Hydraulic-Cement Mortar and Concrete 1
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- C 157/C 157M – 08
| 14. Precision and Bias
14.1 Precision: 14.1.1 When this test method was used for the purpose of determining drying shrinkage of mortar as affected by the choice of portland cement used in making it, the precision was found to be as reported in Test Method C 596 . 14.1.1.1 The following single-laboratory, multiple-operator precision applies to concrete specimens measured at 180 days. 14.1.1.2 For specimens stored in water, the standard devia- tion (1s) among specimens is 0.0045 %. When three replicate specimens are tested, the maximum range among them is not expected to exceed 0.0266 % in 95 % of the sets tested. When a test result represents the mean of three specimens, the 1s is 0.0026 %. The difference between two such means is not expected to exceed 0.0074 % in 95 % of such duplicate tests performed. 14.1.1.3 For specimens stored in air, the standard deviation (1s) among specimens is 0.0084 %. When three replicate specimens are tested, the maximum range among them is not expected to exceed 0.0496 % in 95 % of the sets tested. When a test result represents the mean of 3 specimens, the 1s is 0.0048 %. The difference between two such means is not expected to exceed 0.0137 % in 95 % of such duplicate tests performed. N OTE 5—These precision values were calculated from data taken on specimens described on p. 47 of STP 205, 4 representing 193 concrete mixtures; two specimens made from each of three batches made on separate days, one of each two specimens stored in water, the other stored at nominal 50 % relative humidity. 4 Mather, Bryant, “The Partial Replacement of Portland Cement in Concrete,” Cement and Concrete, ASTM STP 205, ASTM, 1958. C 157/C 157M – 08 6 Copyright by ASTM Int'l (all rights reserved); Thu Apr 16 06:09:51 EDT 2009 Downloaded/printed by Laurentian University pursuant to License Agreement. No further reproductions authorized. 14.2 Bias—No statement on bias is being made since there is no accepted reference material suitable for determining the bias of these procedures. tải về 128.58 Kb. Chia sẻ với bạn bè của bạn:
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