AASHTO T 231-2013 Standard Practice for Capping Cylindrical Concrete Specimens.pdf

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1、TS-3c T 231-1 AASHTO Standard Practice for Capping Cylindrical Concrete Specimens AASHTO Designation: T 231-13 ASTM Designation: C 617-98 (2003) 1. SCOPE 1.1. This method covers apparatus, materials, and procedures for capping freshly molded concrete cylinders with neat cement and hardened cylinders

2、 and drilled concrete cores with high-strength gypsum plaster or sulfur mortar. 1.2. The values stated in SI units are the preferred standard. 1.3. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns associate

3、d with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific precaution statements, see Sections 4.3 and 6.2.4.1. 2. REFERENCED DOCUMENTS 2.1. AASHTO Sta

4、ndards: M 85, Portland Cement M 240M/M 240, Blended Hydraulic Cement T 22, Compressive Strength of Cylindrical Concrete Specimens T 106M/T 106, Compressive Strength of Hydraulic Cement Mortar (Using 50-mm or 2-in. Cube Specimens) 2.2. ASTM Standards: C 287, Standard Specification for Chemical-Resist

5、ant Sulfur Mortar C 472, Standard Test Methods for Physical Testing of Gypsum, Gypsum Plasters and Gypsum Concrete ASTM Manual of Aggregate and Concrete Testing 2.3. ANSI Standard: B 46.1, Standard for Surface Texture, Surface Roughness, Waviness and Lay 3. SIGNIFICANCE AND USE 3.1. This practice de

6、scribes procedures for providing plane surfaces on the end surfaces of freshly molded concrete cylinders, hardened cylinders, or drilled concrete cores when the end surfaces do not conform with the planeness and perpendicularity requirements of applicable standards. 2013 by the American Association

7、of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 231-2 AASHTO 4. CAPPING EQUIPMENT 4.1. Capping PlatesNeat cement caps and high-strength gypsum plaster caps shall be formed against a glass plate at least 6 mm (0.25 in.) thick or

8、a machined metal plate at least 11 mm (0.45 in.) thick (Note 1), on a polished plate of granite or diabase at least 75 mm (3 in.) thick. Sulfur mortar caps shall be formed against similar metal or stone plates. In all cases, plates shall be at least 25 mm (1 in.) greater in diameter than the test sp

9、ecimen and the working surfaces shall not depart from a plane by more than 0.05 mm (0.002 in.) in 150 mm (6 in.). The surface roughness of newly finished metal plates shall not exceed that set forth in Table 4 of the American National Standard for Surface Texture (ANSI B46.1) or 0.003 mm (125 in.) f

10、or any type of surface and direction of lay. The surface when new shall be free of gouges, grooves, or indentations beyond those caused by the finishing operation. Metal plates that have been in use shall be free of gouges, grooves, or indentations greater than 0.25 mm (0.010 in.) deep or greater th

11、an 32 mm2(0.05 in.2) in surface area. If a recess is machined into the metal plate, the thickness of the plate beneath the recessed area shall be at least 13 mm (0.5 in.). In no case shall the recess in the plate be deeper than 13 mm (0.5 in.). Note 1In vertical capping devices, use of two-piece met

12、al capping plates is advantageous as this facilitates refinishing of the capping surface should it become necessary to do so. In such devices, the lower section is a solid plate and the upper section has a circular hole that forms the recess. The two sections are customarily fastened together with m

13、achine screws. It is advantageous to have the upper surface of the lower plate case hardened. A Rockwell hardness of HRC 48 is suggested. 4.2. Alignment DevicesSuitable alignment devices such as guide bars or bulls-eye levels shall be used in conjunction with capping plates to ensure that no single

14、cap will depart from the perpendicularity of the cylindrical specimen by more than 0.5 degrees approximately equivalent to 3.2 mm in 305 mm (0.125 in. in 12 in.). The same requirement is applicable to the relationship between the axis of the alignment device and the surface of a capping plate when g

15、uide bars are used. In addition, the location of each bar with respect to its plate must be such that no cap will be off-centered on a test specimen by more than 1.6 mm (0.06 in.). 4.3. Melting Pots for Sulfur MortarsPots used for melting sulfur mortars shall be equipped with automatic temperature c

16、ontrols and shall be made of metal or lined with a material that is nonreactive with molten sulfur. CautionMelting pots equipped with peripheral heating will ensure against accidents during reheating of cooled sulfur mixtures that have a crusted-over surface. When using melting pots not so equipped,

17、 a buildup of pressure under the hardened surface crust on subsequent reheating may be avoided by use of a metal rod that contacts the bottom of the pot and projects above the surface of the fluid sulfur mix as it cools. The rod should be of sufficient size to conduct enough heat to the top on rehea

18、ting to melt a ring around the rod first and thus avoid the development of pressure. A large metal ladle can be substituted for the rod. Sulfur melting pots should be used under a hood to exhaust the fumes to outdoors. Heating over an open flame is dangerous because the flash point of sulfur is appr

19、oximately 227C (440F) and the mixture can ignite due to overheating. Should the mixture start to burn, covering will snuff out the flame. The pot should be recharged with fresh material after the flame has been extinguished. 5. CAPPING MATERIALS 5.1. The strength of the capping material and the thic

20、kness of the caps shall conform to the requirements of Table 1. 2013 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 231-3 AASHTO Table 1Compressive Strength and Maximum Thickness of Capping Materials

21、 Cylinder Compressive Strength, MPa (psi) Minimum Strength of Capping Material Maximum Average Thickness of Cap Maximum Thickness Any Part of Cap 3.5 to 50 MPa (500 to 7000 psi) 35 MPa (5000 psi) or cylinder strength, whichever is greater 6 mm (0.25 in.) 8 mm (0.31 in.) greater than 50 MPa (7000 psi

22、) Compressive strength not less than cylinder strength, except as provided in Section 5.1.1. 3 mm (0.125 in.) 5 mm (0.20 in.) 5.1.1. If sulfur mortar, high strength gypsum plaster, and other materials except neat cement paste are to be used to test concrete with a strength greater than 50 MPa (7000

23、psi), the manufacturer or the user of the material must provide documentation: that the average strength of 15 cylinders capped with the materials is not less than 98 percent of the average strength of 15 companion cylinders capped with neat cement paste or 15 cylinders ground plane to within 0.05 m

24、m (0.002 in.); that the standard deviation of the strengths of the capped cylinders is not greater than 1.57 times that of the standard deviation of the reference cylinders; that the cap thickness requirements were met in the qualification tests; and of the hardening time of the caps used in the qua

25、lification tests. 5.1.2. Additionally, the qualification test report must include the compressive strength of 50-mm (2-in.) cubes of the material qualified and of neat cement paste cubes, if used. Capping materials conforming to these requirements are permitted to be used for cylinders with strength

26、s up to 20 percent greater than the concrete tested in these qualification tests. The manufacturer must requalify lots of material manufactured on an annual basis or whenever there is a change in the formulation of the raw materials. The user of the material must retain a copy of the qualification r

27、esults, and the dates of manufacture of material qualified and of the material currently being used. (See Table 2.) 2013 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 231-4 AASHTO Table 2Sample Repo

28、rt of Qualifications of a Capping Material Note-Manufacturer: Testing Supplies Co. Capping Material: Super Strong AAA-Sulfur mortar Lot: 12a45 Date Tested: 11/3/98 Signed by:_(Testing Agency and Responsible Official) Item Capping Material Control Cylinders Ratio Criteria Pass/Fail Concrete cylinder

29、test data Type of capping material Sulfur Ground Average concrete strength, MPa (psi) 76.2 (11,061) 75.9 (11,008) 1.005 0.98 Xc Pass Standard deviation MPa (psi) 2.59 (376) 1.72 (250) 1.504 1.57 C Pass Number of cylinders tested 15 15 Cap age when cylinders tested 7 days n/a Capping material test da

30、ta Average cap thickness mm (in.) 2.8 (0.11) n/a Compressive strength of 50-mm (2-in.) cubes, MPa (psi) 91 (12,195) Cube age when tested 7 days Maximum concrete strength qualified, MPa (psi) 1.2 av. str = 91.5 (13,273)aa Nominally a specified strength of 75 MPa (11 000 psi) and perhaps somewhat high

31、er. 5.1.3. The compressive strength of capping materials shall be determined by testing 50-mm (2-in.) cubes following the procedure described in T 106M/T 106. Except for sulfur mortars, molding procedures shall be as in T 106M/T 106 unless other procedures are required to eliminate large entrapped a

32、ir voids. See test methods for alternative compaction procedures. Cure cubes in the same environment for the same length of time as the materials used to cap specimens. 5.1.4. The strength of the capping material shall be determined on receipt of a new lot and at intervals not exceeding 3 months. If

33、 a given lot of the capping material fails to conform to the strength requirements, it shall not be used, and strength tests of the replacement material shall be made weekly until four consecutive determinations conform to specification requirements. 5.2. Neat Hydraulic Cement Paste: 5.2.1. Make the

34、 qualification test of the neat hydraulic cement paste prior to use for capping to establish the effects of water/cement ratio and age on compressive strength of 50-mm (2-in.) cubes (Note 2). Note 2The cements used generally conform to M 85 Types I, II, or III; however, M 240M/M 240 blended cements,

35、 calcium aluminate, or other hydraulic cements producing acceptable strength may be used. 5.2.2. Mix the neat cement paste to the desired consistency at a water/cement ratio equal to or less than that required to produce the required strength, generally 2 to 4 h before the paste is to be used (Note

36、3). Remix as necessary to maintain acceptable consistency (Note 4). Some retempering of the paste is acceptable if the required water/cement ratio is not exceeded. Optimum consistency is generally produced at water/cement ratios of 0.32 to 0.36 by mass for Type I and Type II cements and 0.35 to 0.39

37、 by mass for Type III cements. Note 3Freshly mixed pastes tend to bleed, shrink, and make unacceptable caps. The 2- to 4-h period is generally appropriate for portland cements. 2013 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violat

38、ion of applicable law.TS-3c T 231-5 AASHTO Note 4The required consistency of the paste is determined by the appearance of the cap when it is stripped. Fluid paste results in streaks in the cap. Stiff paste results in thick caps. 5.3. High-Strength Gypsum Cement Paste: 5.3.1. No fillers or extenders

39、may be added to neat high-strength gypsum cement paste subsequent to the manufacture of the cement (Note 5). Qualification tests shall be made to determine the effects of water/cement ratio and age on the compressive strength 50-mm (2-in.) cubes. Retarders may be used to extend working time, but the

40、ir effects on required water/cement ratio and strength must be determined (Note 6.) Note 5Low-strength molding plaster, plaster of paris, or mixtures of plaster of paris and portland cement are unsuitable for capping. Note 6The water/gypsum cement ratio should be between 0.26 and 0.30. Use of low wa

41、ter/cement ratios and vigorous mixing will usually permit development of 35 MPa (5000 psi) at ages of 1 to 2 h. Higher water/gypsum cement ratios extend working time, but reduce strength. 5.3.2. Mix the neat gypsum cement paste at the desired water/cement ratio and use it promptly because it sets ra

42、pidly. 5.4. Sulfur Mortar: 5.4.1. Proprietary or laboratory prepared sulfur mortars are permitted if allowed to harden a minimum of 2 h before testing concrete with strength less than 35 MPa (5000 psi). For concrete strengths of 35 MPa (5000 psi) or greater, sulfur mortar caps must be allowed to har

43、den at least 16 h before testing, unless a shorter time has been shown to be suitable as specified in Section 5.1.1. 5.4.2. Determination of Compressive StrengthPrepare test specimens using a cube mold and base plate conforming to the requirements of T 106M/T106 and a metal cover plate conforming in

44、 principle to the design shown in Figure 1 (Note 7). Bring the various parts of the apparatus to a temperature of 20 to 30C (68 to 86F), lightly coat the surfaces that will be in contact with the sulfur mortar with mineral oil and assemble near the melting pot. Bring the temperature of the molten su

45、lfur mortar in the pot within a range of 129 to 143C (265 to 290F), stir thoroughly, and begin casting cubes. Using a ladle or other suitable pouring device, quickly fill each of the three compartments until the molten material reaches the top of the filling hole. Allow sufficient time for maximum s

46、hrinkage, due to cooling, and solidification to occur (approximately 15 min) and refill each hole with molten material (Note 8). After solidification is complete, remove the cubes from the mold without breaking off the knob formed by the filling hole in the cover plate. Remove oil, sharp edges, and

47、fins from the cubes and check the planeness of the bearing surfaces in the manner described in T 106M/T 106. After storage at room temperature to the desired age, but not less than 2 h, test cubes in compression following the procedure described in T 106M/T 106 and calculate the compressive strength

48、 in MPa (psi). 2013 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 231-6 AASHTO Dimensional Equivalents mm 6.4 12.7 22.2 44.5 100 250 in. 1/41/27/813/44 10Notes: All dimensions shown in millimeters u

49、nless otherwise noted. Figure 1Sketch of Cover for 50-mm (2-in.) Cube Mold Note 7If desired, a plain phenol formaldehyde (bakelite) plate of 3-mm (0.125-in.) thickness, provided with three appropriately spaced filling holes, may be inserted between the cover plate and the mold to slow the rate of cooling of test specimens. Note 8The second filling helps to prevent the formation of a large void or shrinkage pipe in the body of a cube. However, such defects may occur no matter how much care