AASHTO R 72-2016 Standard Practice for Match Curing of Concrete Test Specimens.pdf

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1、Standard Practice for Match Curing of Concrete Test Specimens AASHTO Designation: R 72-161 Release: Group 1 (April 2016) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3c R 72-1 AASHTO Standard Practice for Match

2、Curing of Concrete Test Specimens AASHTO Designation: R 72-161Release: Group 1 (April 2016) 1. SCOPE 1.1. This recommended practice covers procedures for making and curing cylindrical concrete specimens at the same temperature as that measured in a concrete member. 1.2. The concrete sample used to m

3、ake the specimens shall be taken from the concrete being placed in the same member where the temperature is to be measured. 1.3. This procedure can be deployed with confidence for both air chamber and insulated jacket (Surecure) systems and for both molded cylinders with nominal diameter to height d

4、imensions of 100 by 200 mm (4 by 8 in.) or 150 by 300 mm (6 by 12 in.). However, users should be watchful of Type I error for air chamber systems and Type II error with insulated jacket mold systems. A Type I error represents the situation where loss of temperature control occurs over only a portion

5、 of the entire match-cure duration where control is later regained. A Type II error represents the situation where a constant level of temperature control error occurs during the entire match-cure duration. 1.4. The values stated in SI units are to be regarded as the standard. 1.5. This standard doe

6、s not purport to address all of the safety concerns, if any, 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. 2. REFERENCED DOCUMENTS 2.1. AASHTO

7、 Standards: M 205M/M 205, Molds for Forming Concrete Test Cylinders Vertically R 60, Sampling Freshly Mixed Concrete T 23, Making and Curing Concrete Test Specimens in the Field T 119M/T 119, Slump of Hydraulic Cement Concrete T 152, Air Content of Freshly Mixed Concrete by the Pressure Method T 196

8、M/T 196, Air Content of Freshly Mixed Concrete by the Volumetric Method 2.2. ASTM Standards: C125, Standard Terminology Relating to Concrete and Concrete Aggregates C1064/C1064M, Standard Test Method for Temperature of Freshly Mixed Hydraulic-Cement Concrete 2016 by the American Association of State

9、 Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c R 72-2 AASHTO 3. TERMINOLOGY 3.1. For definitions of terms used in this practice, refer to ASTM C125. 4. SIGNIFICANCE AND USE 4.1. This method provides a procedure for curing concrete cylind

10、ers at the same temperature as that monitored at a specific location in a concrete member. Consequently, the compressive strength of the cylinder more accurately represents the in-place concrete strength of the member. The method is particularly useful for determining the concrete compressive streng

11、th at early ages in the fabrication of precast concrete members or for determining the compressive strength of concrete at a critical location in a structural member. 5. APPARATUS 5.1. The apparatus shall consist of a monitoring and heating system capable of maintaining concrete cylinders at a tempe

12、rature within 2C (4F) of the temperature of the concrete at a specific location in the member. A satisfactory system may include a temperature sensor in the member, a controller, special insulated cylinder molds with built-in heating systems, and a temperature sensor in the molds. 5.2. Temperature S

13、ensor in the MemberTemperature sensors shall be placed at the most critical locations for strength development. The purchaser shall determine the critical locations for temperature sensors in each type of member and show the locations on the project drawings or the contractor shall submit drawings s

14、howing proposed locations to the purchaser for approval. 5.2.1. Temperature sensor wire shall be durable enough to withstand the wear associated with construction operations and shall have a size of 20 awg or larger in diameter (Note 1). Note 1In locations where electrical interference may affect th

15、e measured data, shielded wire should be used. 5.3. ControllerThe controller shall be capable of monitoring the temperatures of the member and cylinders and controlling the heating system to maintain the cylinder temperature within +2C (+4F) of the temperature measured in the member. Proper operatio

16、n of the system shall be verified on a regular basis in accordance with the manufacturers recommendations. 5.4. Cylinder Molds: 5.4.1. Cylinder molds shall conform to the requirements of M 205M/M 205 for reusable molds and shall be fitted with watertight lids to prevent moisture loss. 5.4.2. Cylinde

17、r molds shall have inside nominal diameter by height dimensions of 100 by 200 mm (4 by 8 in.) or 150 by 300 mm (6 by 12 in.). 5.4.3. When heated cylinder molds are used, they shall have built-in thermocouples that sense the temperature of the concrete specimens. Each cylinder mold shall have a heati

18、ng element that surrounds the core of the mold, provides uniform heat to the concrete specimen, and is capable of maintaining a cylinder temperature that matches the temperature of the concrete member within the stated tolerance (Note 2). Note 2Because the match-curing system only provides heat to t

19、he cylinder and cannot cool it, the temperature of the cylinder may exceed that of the member if the temperature of the member decreases at a greater rate than that of the cylinder. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a v

20、iolation of applicable law.TS-3c R 72-3 AASHTO 6. TEST SPECIMENS 6.1. Test specimens shall be cylinders of concrete cast and hardened in an upright position, with a length equal to twice the diameter. When the nominal maximum size of coarse aggregate does not exceed 50 mm (2 in.), the cylinder may b

21、e 150 by 300 mm (6 by 12 in.). When the nominal maximum size of coarse aggregate does not exceed 25 mm (1 in.), the cylinder may be 100 by 200 mm (4 by 8 in.). 6.2. A minimum of two 150-by-300-mm (6-by-12-in.) or three 100-by-200-mm (4-by-8-in.) cylinders shall be made for each strength test when th

22、e specified strength does not exceed 34 MPa (5000 psi). A minimum of three cylinders shall be made for each strength test when the specified strength exceeds 34 MPa (5000 psi). 7. PROCEDURE 7.1. System InstallationPrior to concrete placement, the temperature sensors in the member shall be securely f

23、ixed at the specified locations. The sensor tips shall be installed such that they do not have direct contact with steel reinforcement. Prior to concrete placement, proper operation of the match-curing system shall be verified in accordance with the manufacturers recommendations. 7.2. Sampling Concr

24、eteThe samples used to fabricate test specimens under this standard shall be obtained in accordance with R 60 unless an alternative procedure has been approved. The concrete sample shall be taken from concrete placed as close as practical to the temperature sensor in the member. 7.3. Slump, Air Cont

25、ent, and Temperature: 7.3.1. SlumpMeasure and record the slump of each batch of concrete from which specimens are made, immediately after remixing in the receptacle as required by T 119M/T 119. 7.3.2. Air ContentDetermine and record the air content in accordance with either T 152 or T 196M/T 196. Th

26、e concrete used in performing the air content test shall not be used in fabricating test specimens. 7.3.3. TemperatureDetermine and record the concrete temperature in accordance with ASTM C1064/C1064M. 7.4. Molding SpecimensTest specimens shall be molded using the procedures of T 23. 7.5. Match Curi

27、ng: 7.5.1. Covering after FinishingImmediately after finishing, precautions shall be taken to prevent evaporation and loss of water from the specimens. Cover specimens with a nonabsorbent, nonreactive plate or a sheet of impervious plastic. 7.5.2. Specimen StorageDuring match curing, molds and speci

28、mens shall be shielded from direct rays of the sun, other heating devices, rain, and wind. All molds controlled by the same controller shall be stored together (Note 3). Note 3Because the match-curing system only provides heat to the cylinders, better temperature control is obtained when the cylinde

29、rs are stored in an environment that is cooler than the temperature of the concrete in the member. 7.5.3. Connect the molds to the controller and match cure for the specified length of time. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplicati

30、on is a violation of applicable law.TS-3c R 72-4 AASHTO 7.5.4. Following the match-curing period, the cylinders shall be removed from the molds and subsequently stored in a similar temperature and moisture environment as the member unless stated otherwise in the project specifications. 7.5.5. When m

31、atch-cured cylinders are used to determine concrete release strengths, it is recommended that match curing be continued for as long as possible and until the cylinders are stripped for testing. 1Formerly AASHTO Provisional Standard PP 54. First published as a full standard in 2016. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.