Specifications Vol. II - Laserfiche WebLink

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..., . .., . (a) For precast drainage systems that are manufactured at the precast plant the Contractor is permitted to use concrete meeting the requirements of ASTM C 478 ,., [ASTM C 478M] 4,000 psi [30 MPa] in lieu of Class I or Class II concrete. Apply the . chloride content limits specified in 346-4.2 to all box culverts. (b) The Engineer may allow higher target slump, not to exceed 7 inches ,., [180 mm], when a Type F or Type G admixtures is used. . (c) The Engineer may approve a reduction in the target slump for slip-form operations. .., (d) When the use of silica fume or meta kaolin is required as a pozzolan in Class V, Class V (Special) or Class VI concrete, ensure that the concrete does not exceed a permeability of 1,000 coulombs at 28 days, when tested per AASHTO T 277. Submit 2, 4 x 8 inches [102 x 203 mm] cylindrical test specimens to the Engineer for permeability testing before mix design approval. Take the permeability test specimens from the concrete of the laboratory trial batch or from the field trial batch of at least 3 yd3 [2.3 m3]. Verify the mix proportioning of the designed mix and take representative samples of trial batch concrete for the required plastic and hardened property tests. Cure the field trial batch specimens similar to the standard laboratory curing methods. Submit the permeability test specimens at least 7 days prior to the scheduled 28 day test. The average permeability of the two tests, one test per cylinder, is considered the rapid chloride permeability of the concrete mix. In lieu of rapid chloride permeability test and prior to mix design approval, submit three test cylinders to the Engineer for performing of surface resistivity test in accordance with FM 5-578. Ensure that the result of the average 28 day surface resistivity value of the concrete samples remains greater than or equal to 37 KOhm-cm. (e) The Engineer may allow a target slump of 9.0 inches [230 mm] when Type I or II admixture is used to produce flowing concrete in the construction of precast concrete products. 346-3.2 Drilled Shaft Concrete: When drilled shaft concrete is placed in any wet shaft, provide concrete in accordance with the following specified slump loss requirements. When concrete is placed in a dry excavation, do not test for slump loss, except where a temporary removable casing is to be used. Ensure that drilled shaft concrete has a slump between 7 inches and 9 inches [175 mm and 225 mm] when placed and maintains a slump of 4 inches [100 mm] or more throughout the drilled shaft concrete elapsed time. Ensure that the slump loss is gradual as evidenced by slump loss tests described below. The concrete elapsed time is the sum of the mixing and transit time, the placement time and the time required for removal of any temporary casing that causes or could cause the concrete to flow into the space previously occupied by the temporary casing. Provide slump loss tests before drilled shaft concrete operations begin, demonstrating that the drilled shaft concrete maintains a slump of at least 4 inches [100 mm] throughout the concrete elapsed time. Inform the Engineer at least 48 hours before performing such tests. Perform slump loss testing of the drilled shaft mix using a laboratory acceptable to the Engineer meeting the requirements of 6-9. Perform the following procedures for slump loss tests: C1) Prepare the mix for the slump loss test at a temperature consistent with the highest ambient and concrete temperatures expected during actual concrete placement. Obtain the Engineer's approval of the test temperature. ,., . -, . ,.., . .., . .., . 1""1 . .., . - .., . .., . .., . I""J . ,., . ...... . ..... 09/09 01000-93 03-4122.F .