1、Standard Method of Test for Capping Cylindrical Concrete Specimens AASHTO Designation: T 231-17 Technical Section: 3c, Hardened Concrete Release: Group 1 (April 2017) ASTM Designation: C617-15 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249
2、 Washington, D.C. 20001 TS-3c T 231-1 AASHTO Standard Method of Test for Capping Cylindrical Concrete Specimens AASHTO Designation: T 231-17 Technical Section: 3c, Hardened Concrete Release: Group 1 (April 2017) ASTM Designation: C617-15 1. SCOPE 1.1. This method covers apparatus, materials, and pro
3、cedures for capping freshly molded concrete cylinders with neat cement and hardened cylinders and drilled concrete cores with high-strength gypsum plaster or sulfur mortar. 1.2. The values stated in SI units or inch-pound units are to be regarded separately as standard. The values stated in each sys
4、tem may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard. 1.3. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to ad
5、dress all of the safety concerns associated 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.
6、1. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 85, Portland Cement M 240M/M 240, Blended Hydraulic Cement T 106M/T 106, Compressive Strength of Hydraulic Cement Mortar (Using 50-mm or 2-in. Cube Specimens) 2.2. ASTM Standards: C287, Standard Specification for Chemical-Resistant Sulfur Mortar C1
7、231/C123M, Standard Practice for Use of Unbonded Caps in Determination of Compressive Strength of Hardened Concrete Cylinders 2.3. ANSI Standard: B 46.1, Standard for Surface Texture, Surface Roughness, Waviness and Lay 2017 by the American Association of State Highway and Transportation Officials.A
8、ll rights reserved. Duplication is a violation of applicable law.TS-3c T 231-2 AASHTO 3. SIGNIFICANCE AND USE 3.1. This practice describes procedures for providing plane surfaces on the end surfaces of freshly molded concrete cylinders, hardened cylinders, or drilled concrete cores when the end surf
9、aces do not conform with the planeness and perpendicularity requirements of applicable standards. ASTM C1231/C123M describes alternative procedures using unbonded caps or pad caps. 4. CAPPING EQUIPMENT 4.1. Capping PlatesNeat cement caps and high-strength gypsum plaster caps shall be formed against
10、a glass plate at least 6 mm (0.25 in.) thick or 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
11、mm (1 in.) greater in diameter than the test specimen 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 Surfa
12、ce Texture (ANSI B 46.1) or 0.003 mm (125 in.) for 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 gre
13、ater than 0.25 mm (0.010 in.) deep or greater than 32 mm2(0.05 in.2) in surface area. Note 1A 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 ca
14、p will depart from the perpendicularity of the cylindrical specimen by more than 0.5 degrees (see Note 2). The same requirement is applicable to the relationship between the axis of the alignment device and the surface of a capping plate when guide bars are used. In addition, the location of each ba
15、r 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.). Note 2A deviation from perpendicularity of 0.5 degrees is equal to a slope of approximately 1 mm in 100 mm (1/4in. in 12 in.). 4.3. Melting Pots for Sulfur MortarsPots used fo
16、r melting sulfur mortars shall be equipped with automatic temperature controls 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 tha
17、t have a crusted-over surface. When using melting pots not so equipped, 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
18、should be of sufficient size to conduct enough heat to the top on reheating 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 ov
19、er an open flame is dangerous because the flash point of sulfur is approximately 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. C
20、APPING MATERIALS 5.1. The strength of the capping material and the thickness of the caps shall conform to the requirements of Table 1. 2017 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
21、 Table 1Compressive Strength and Maximum Thickness of Capping Materials 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 i
22、s greater 6 mm (0.25 in.) 8 mm (0.31 in.) Greater than 50 MPa (7000 psi) 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
23、 to be used to test concrete with a strength greater than 50 MPa (7000 psi), the manufacturer or the user of the material must provide documentation: 5.1.1.1. That the average strength of 15 cylinders capped with the materials is not less than 98 percent of the average strength of 15 companion cylin
24、ders capped with neat cement paste or 15 cylinders ground plane to within 0.05 mm (0.002 in.); 5.1.1.2. 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; 5.1.1.3. That the cap thickness requi
25、rements were met in the qualification tests; and 5.1.1.4. Of the hardening time of the caps used in the qualification 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 us
26、ed. Capping materials conforming to these requirements are permitted to be used for cylinders with strengths 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
27、in the formulation of the raw materials. The user of the material must retain a copy of the qualification results, and the dates of manufacture of material qualified and of the material currently being used (see Table 2). 2017 by the American Association of State Highway and Transportation Officials
28、.All rights reserved. Duplication is a violation of applicable law.TS-3c T 231-4 AASHTO Table 2Sample Report 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
29、 Responsible Official) Item Capping Material Control Cylinders Ratio Criteria Pass/Fail Concrete cylinder 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
30、 C Pass Number of cylinders tested 15 15 Cap age when cylinders tested 7 days n/a Capping material test data 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
31、 av. str = 91.5 (13,273)aa Nominally a specified strength of 75 MPa (11,000 psi) and perhaps somewhat higher. 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
32、procedures shall be as in T 106M/T 106 unless other procedures are required to eliminate large entrapped air 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 th
33、e capping material shall be determined on receipt of a new lot and at intervals not exceeding 3 months. If 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 consecuti
34、ve determinations conform to specification requirements. 5.2. Neat Hydraulic Cement Paste: 5.2.1. Make the 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 3). No
35、te 3The cements used generally conform to M 85 Types I, II, or III; however, M 240M/M 240 blended cements, 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 tha
36、n that required to produce the required strength, generally 2 to 4 h before the paste is to be used (Note 4). Remix as necessary to maintain acceptable consistency (Note 5). Some retempering of the paste is acceptable if the required water/cement ratio is not exceeded. Optimum consistency is general
37、ly 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 by mass for Type III cements. Note 4Freshly mixed pastes tend to bleed, shrink, and make unacceptable caps. The 2- to 4-h period is generally appropriate for portland cements. Note 5The require
38、d 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. 2017 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of a
39、pplicable law.TS-3c T 231-5 AASHTO 5.3. High-Strength Gypsum Cement Paste: 5.3.1. No fillers or extenders may be added to neat high-strength gypsum cement paste subsequent to the manufacture of the cement (Note 6). Qualification tests shall be made to determine the effects of water/cement ratio and
40、age on the compressive strength 50-mm (2-in.) cubes. Retarders may be used to extend working time, but their effects on required water/cement ratio and strength must be determined (Note 7). Note 6Low-strength molding plaster, plaster of paris, or mixtures of plaster of paris and portland cement are
41、unsuitable for capping. Note 7The water/gypsum cement ratio should be between 0.26 and 0.30. Use of low water/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.
42、Mix the neat gypsum cement paste at the desired water/cement ratio and use it promptly because it sets rapidly. 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 (500
43、0 psi). For concrete strengths of 35 MPa (5000 psi) or greater, sulfur mortar caps must be allowed to harden 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 cub
44、e mold and base plate conforming to the requirements of T 106M/T106 and a metal cover plate conforming in principle to the design shown in Figure 1 (Note 8). 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
45、 sulfur mortar with mineral oil and assemble near the melting pot. Bring the temperature of the molten sulfur 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 compar
46、tments until the molten material reaches the top of the filling hole. Allow sufficient time for maximum shrinkage, due to cooling, and solidification to occur (approximately 15 min) and refill each hole with molten material (Note 9). After solidification is complete, remove the cubes from the mold w
47、ithout breaking off the knob formed by the filling hole in the cover plate. Remove oil, sharp edges, and 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 cube
48、s in compression following the procedure described in T 106M/T 106 and calculate the compressive strength in MPa (psi). 2017 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 Notes: All dim
49、ensions shown in millimeters unless otherwise noted. Dimensional Equivalents mm 6.4 12.7 22.2 44.5 100 250 in. 1/41/27/813/44 10 Figure 1Sketch of Cover for 50-mm (2-in.) Cube Mold Note 8If 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 9The second filling helps to prevent the formation of a large void
