360R-06 Design of Slabs-on-Ground
—Inspection and site testing of slab support
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| 3.7—Inspection and site testing of slab support
Inspection and testing are required to control the quality of the subgrade and subbase construction and to determine if it conforms to the project specifications. Before construction begins, the subgrade soils and any subbase or base-course materials should be sampled, tested in the laboratory, and the results evaluated. In general, particle size (ASTM D 422), plasticity (ASTM D 4318), and laboratory compaction tests (ASTM D 698 or 1557) are performed on soils and soil- aggregate mixtures. For cohesionless and free-draining soils and aggregates gradation, determination of maximum relative density (ASTM D 4253) and minimum relative density (ASTM D 4254) and calculation of relative density may be appropriate. After compaction, the in-place density to calculate the percent compaction can be determined in the field by any of several methods: drive cylinder (ASTM D 2937); sand cone (ASTM D 1556); water balloon (ASTM D 2167); or nuclear densometer (ASTM D 2922 and D 3017). Although the sand cone test is the most accepted method, the nonde- structive nuclear density method is advantageous because it is accomplished in a few minutes, and the results are avail- able at the end of the field test. Because this allows the field density and moisture contents to be used to control construction, the nuclear density method is widely used and accepted. To check questionable results or to confirm calibrations, however, the sand cone method is generally specified. To check the nuclear gauge against the sand cone and provide an adjustment factor, a series of calibration tests are run. The moisture readings must also be checked against field moisture tests (ASTM D 566). Testing frequency is related to the uniformity of the materials being used and the quality of compaction required. Work that does not conform to the project specifications should be corrected and retested. The subgrade should be tested in advance of the installation of the remainder of the slab-on-ground system. Minimum testing requirements should be established for each project. These should provide a reasonable test interval to be taken in each lift. These tests are relatively inexpensive and easy to perform. tải về 2.35 Mb. Chia sẻ với bạn bè của bạn:
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