1、Standard Specification for Corrosion-Resistant Coated Dowel Bars AASHTO Designation: M 254-06 (2015) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001TS-4g M 254-1 AASHTO Standard Specification for Corrosion-Resistant C
2、oated Dowel Bars AASHTO Designation: M 254-06 (2015) 1. SCOPE 1.1. This specification covers the materials, manufacture, and installation of coated dowel bars to be used where corrosion-resistant performance is essential and may be used in lieu of stainless or other approved noncorrosive metals. The
3、 dowel shall consist of a steel core covered by an organic coating. 1.2. The coated dowels shall be one of the two following types: Type AThe coating material develops sufficiently low-bond strength with concrete that a bond breaker is not required. Type BThe coating material develops bond strength
4、with concrete such that a bond breaker is required. The type of bond breaker used shall be as recommended by the coating manufacturer. 1.3. The values stated in SI units are to be regarded as the standard. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 255M/M 255, Steel Bars, Carbon, Hot-Wrought,
5、Special Quality, Mechanical Properties T 253, Coated Dowel Bars 2.2. ASTM Standard: G12, Standard Test Method for Nondestructive Measurement of Film Thickness of Pipeline Coatings on Steel (Withdrawn 2013) 2.3. Other Reference: FHWA-RD-74-18, “Nonmetallic Coating for Concrete Reinforcing Bars,” 1974
6、 3. GENERAL REQUIREMENTS 3.1. The coated dowels shall resist corrosion and degradation caused by roadway deicing materials and normal highway debris. 3.2. The coating shall develop low-bond strengths with portland cement concrete without a bond breaker, if Type A, or with the proper bond breaker, if
7、 Type B. 3.3. The coating shall resist wear due to abrasion resulting from pavement expansion and contraction. 3.4. The coating used over the steel core shall be continuous on the lateral surface of the dowel. 2015 by the American Association of State Highway and Transportation Officials.All rights
8、reserved. Duplication is a violation of applicable law.TS-4g M 254-2 AASHTO 3.5. Test procedures as stated herein and in T 253 shall apply to both Type A and Type B dowels. 3.6. In the event there is any change in material composition or geometrics of the joint support system, any or all parts of th
9、e dowels and assembly are subject to retesting. The frequency of qualification testing will be determined by the purchasing agency. 3.7. The processing facilities of the manufacturer and the fabricator shall be open to inspection by the agent of the purchaser at all times during the manufacturing an
10、d fabricating of the material. 3.8. A minimum of 24 dowel bars shall be made available for testing. Of these, a maximum of six bars may be in a basket assembly. 4. MATERIALS 4.1. The core material shall be made of steel meeting the requirements of M 255M/M 255. The grade shall be as specified by the
11、 purchasing agency. 4.2. The coating material shall be of organic composition with the exception of the pigment, which may or may not be present, and which may have an inorganic composition. Note 1The Type B coating material may be one of the types recommended in Report No. FHWA-RD-74-18 or other ty
12、pes approved by the purchasing agency. 5. DIMENSIONS 5.1. The core metal shall be 31.8-mm (11/4-in.) diameter or as specified by the purchasing agency. 5.2. The nonabraded thickness of the Type A coating shall be 0.64 0.13 mm (25 5 mils). The nonabraded thickness of the Type B coating shall be 0.18
13、0.05 mm (7 2 mils). 5.3. Coating thickness shall be determined according to ASTM G12 or by stripping the coating from the bar. 5.4. The dowels shall be supplied to lengths and in support assemblies or baskets as specified by the purchasing agency. 6. PHYSICAL REQUIREMENTS 6.1. The free ends of the d
14、owels shall be saw cut and free of burrs and projections. 6.2. Dowel coatings shall be free from contamination, perforations, cracks, and holidays (pinholes not visually discernible). Checking for holidays shall be performed by the electric-resistance process. A 67.5-V holiday detector shall be used
15、, as recommended by the manufacturer of the test equipment, for the determination of holidays. 6.3. Any damage that results from welding or mechanical fixation to achieve a fixed-end condition shall not extend more than 25.4 mm (1 in.) in from the weld or point of fixation. 6.4. Welding to achieve a
16、 fixed-end condition shall be sufficiently strong to maintain dowel alignment under the forces imposed by concrete placement and construction practices. 6.5. When tested in accordance with T 253, the dowel bars shall have the following properties: 2015 by the American Association of State Highway an
17、d Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-4g M 254-3 AASHTO 6.5.1. Load DeflectionThe relative deflection shall not exceed 0.25 mm (0.10 in.) at the 1815-kg (4000-lb) load for any of the three specimens tested. 6.5.2. PulloutThe maximum pullout l
18、oad shall not exceed 1360 kg (3000 lb) for any specimens, and no specimen shall show any corrosion, tears, or perforation due to the pullout and subsequent freeze-thaw testing. 6.5.3. AbrasionThe coating shall not have been worn away, perforated, or wrinkled, and none of the three specimens shall sh
19、ow depth or wear exceeding 70 percent of the original coating thickness. Thickness shall be determined according to Section 5.3 of this specification. 6.5.4. CorrosionNo corrosion shall be apparent on any of the specimens when viewed under five-power magnification. 6.5.5. Chemical ResistanceThe coat
20、ing shall not blister, soften, disbond, develop holidays, nor exhibit any undercutting at the drilled holes. 6.5.6. Cathodic DisbondingNo film failure shall take place during the first 1 h of testing. Such film failure would be evidenced by the evolution of hydrogen gas at the cathode or appearance
21、of corrosion products of steel at the anodes except that such hydrogen evolution or corrosion products at the intentionally cut 6.4-mm (1/4-in.) holes will not be considered as basis for rejection. However, no undercutting shall be permitted during the remainder of the test period at the intentional
22、ly cut 6.4-mm (1/4-in.) holes in either the anode or cathode. 6.5.7. Coating HardnessThe hardness of the coating shall exceed the Knoop Hardness Number of 16. 6.5.8. Coating Impact ResistanceNo shattering or disbonding of the coating shall occur except at the impact area (area permanently deformed b
23、y the tup). 7. SAMPLING 7.1. A minimum of 24 dowel bars, of which up to 6 may be in a basket assembly, shall be furnished by the manufacturer for testing and verification of the materials and process. The specimens shall be made available to the testing laboratory 120 days prior to their first inten
24、ded use. When fixed mechanical assembly is being used, a complete assembly with dowels shall be made available upon request by the purchasing agency. 8. DOCUMENTATION 8.1. Tests performed according to this specification shall be the responsibility of the manufacturers and/or coating applicator and m
25、ay be performed at his laboratory or an independent laboratory approved by the purchasing agency. Upon completion of the tests, all tested specimens shall be properly labeled as to test procedure, and be made available upon request to the purchasing agency. 8.2. The laboratory facilities and procedu
26、re must be open to observation by the purchaser while tests are underway. The purchasing agency reserves the right to check any or all parts of the required tests in the agency laboratory or a laboratory of his choice. 8.3. The coated dowel manufacturer and/or coating applicator shall provide certif
27、ied copies of test reports to the purchasing agency showing all test data. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-4g M 254-4 AASHTO 8.4. For the purpose of identification, the manufacturer or
28、 applicator shall provide certification showing the generic type of coating material along with the type and percentages of pigments, diluents, fillers, flexibilizers, and other additives used. 8.5. The coated dowel manufacturer is defined as a company that produces a complete product consisting of
29、dowel bar and coating. 8.6. The coating applicator is defined as a company that applies coatings to dowel bars. 8.7. Rechecks of the coated dowels may be made at the discretion of the purchasing agency. The purchasing agency may delete any of the above specified test procedures during rechecks of any previously approved product. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
