Masonry Magazine January 1976 Page.20
FIG. 2
E 149 Test Setup
measure the compatibility (flexural bond strength) between the masonry units and mortars.
Another method of test which determines the bond strength is ASTM E 149. See Fig. 2. This method of test is not widely used and is not recommended, since it is difficult to achieve reproducible results.
Companion Specimens. The method of determination of allowable tensile stresses (E 72) was described in detail in Technical Notes 39A. When this testing is being performed, companion flexural beams may be built and tested in accordance with E 518. A minimum of 3 beams should be built, using the same units, mortar and workmanship as described in Technical Notes 39A for the E 72 transverse strength specimens. After testing the E 72 specimen and the companion beams at the age of 28 days, the relationship between the wall and beam strengths can be obtained.
Once this relationship has been established, the E 72 tests need not be used to maintain a quality control check. E 518 is more suitable for quality control as it uses much smaller assemblages, does not require large specially equipped laboratories and is more economical. E 518 tests should not be used to determine flexural transverse design stresses.
Test Specimens. E 518 provides two methods for performing the test on the flexural beams. Method A provides for concentrated loads at 1/3 points of the span. (See Fig. 3.) Method B provides for a uniform loading over the entire span. (See Fig. 4.) This is usually accomplished by using an air bag. The prisms for quality control testing shall be built at the job site with the materials and workmanship being the same as the actual construction.
When E 518 is used for determination of unit compatibility with high-bond mortars, the materials shall be as specified, but the workmanship is limited to "inspected workmanship". Each test shall consist of a minimum of 5 prisms. All joints shall be 3/8 in. (0.95 cm) ± 1/16 in. (0.16 cm). The joints on the finished
FIG. 3
E 518 Method A Test Setup
FIG. 4
E 518 Method B Test Setup
face shall be tooled the same as for the actual construction.
Those prisms constructed in the field for quality assurance testing shall be built in an area where they are protected from damage, but exposed to the same climatological conditions as the job constructed masonry. These prisms should be stored at the job site until just prior to testing.
Laboratory Procedures. While ASTM E 518 does not specifically so state, the specimens for both Method A and Method B (see Figs. 5 and 6) should be placed with the tooled joints downward; that is, the loadings should be applied to the unfinished face. This provides a more standardized test and allows a more accurate comparison of results.
If Method A, third point loading, is used and failure on any specimen occurs outside of the middle third of the specimen, the test results for that specimen shall be discarded.
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