360R-06 Design of Slabs-on-Ground
R-16 ACI COMMITTEE REPORT
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- DESIGN OF SLABS-ON-GROUND 360R-17
| 360R-16
ACI COMMITTEE REPORT broken pipes in the subgrade. Because there can be a variety of sources of moisture, there is likely to be a nonuniform distribution of moisture beneath the slab-on-ground. Tests can be made to try to ascertain the moisture problem before a covering is placed. ASTM D 4263 will detect the presence of moisture coming through the slab, but it will not yield a rate of moisture movement. A quantitative test method, ASTM F 1869, uses a desiccant calcium chloride beneath an impermeable dome over a small slab area to calculate the moisture emission rate. These test results, however, may be misleading if the ambient air conditions do not represent those for in-service conditions. ASTM F 1869 requires an ambient air temperature of 75 °F ± 10 °F (24 ºC ± 6 ºC) and a relative humidity of 50% ± 10% for 48 hours before and during the test. In addition, the test has been found to measure only the moisture in the top 1/2 in. (13 mm) of the Fig. 3.7—Decision flowchart to determine if a vapor retarder/barrier is required and where it is to be placed. DESIGN OF SLABS-ON-GROUND 360R-17 slab, and cannot detect moisture below a depth of 3/4 in. (19 mm). To better quantify moisture in slabs, ASTM F 2170 was developed for the use of relative humidity probes. Drainage of the subgrade and the selection of subgrade materials will have a great influence on the performance of vapor retarders/barriers. Also, protection of the vapor retarders/barriers from damage during construction can significantly influence the retarder/barrier’s effectiveness. Vapor retarders/barriers have been reported to affect the behavior of the concrete in the slab by increasing finishing time, promoting cracking, increasing slab curling, and reducing strength. These problems, however, may be less costly than performance failures related to excessive moisture emission from the slab surface. tải về 2.35 Mb. Chia sẻ với bạn bè của bạn:
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