1、Standard Method of Test for Coefficient of Thermal Expansion of Hydraulic Cement Concrete AASHTO Designation: T 336-151American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3c T 336-1 AASHTO Standard Method of Test for C
2、oefficient of Thermal Expansion of Hydraulic Cement Concrete AASHTO Designation: T 336-1511. SCOPE 1.1. This test method covers determination of the coefficient of thermal expansion (CTE) of hydraulic cement concrete cores and cylinders. Because it is known that the degree of saturation of concrete
3、influences its measured coefficient of thermal expansion, the specimens must be in a saturated condition for this procedure. 1.2. The values stated in SI units shall be regarded as the standard. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: R 39, Making and Curing Concrete Test Specimens in the Lab
4、oratory T 22, Compressive Strength of Cylindrical Concrete Specimens T 23, Making and Curing Concrete Test Specimens in the Field T 24M/T 24, Obtaining and Testing Drilled Cores and Sawed Beams of Concrete 2.2. ASTM Standards: C670, Standard Practice for Preparing Precision and Bias Statements for T
5、est Methods for Construction Materials E228, Standard Test Method for Linear Thermal Expansion of Solid Materials with a Push-Rod Dilatometer E289, Standard Test Method for Linear Thermal Expansion of Rigid Solids with Interferometry 3. SUMMARY OF TEST METHOD 3.1. This method determines the CTE of a
6、 cylindrical concrete specimen, maintained in a saturated condition, by measuring the length change of the specimen due to a specified temperature change. The measured length change is corrected for any change in length of the measuring apparatus (previously determined), and the CTE is then calculat
7、ed by dividing the corrected length change by the temperature change and then the specimen length, as described in the section on calculations. 4. SIGNIFICANCE AND USE 4.1. Measurement of the CTE permits assessment of the potential for length/volume change of concrete due to a uniform temperature ch
8、ange and of the potential deformation of a concrete structure due to a temperature gradient through the concrete. As an example, for pavement slabs 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T
9、 336-2 AASHTO on grade, uniform temperature change will affect the openings at joints and a temperature gradient through the thickness of these same slabs will produce curling of the slabs. The results of this test can be used to better estimate slab movement and stress development due to temperatur
10、e change. 5. APPARATUS 5.1. Concrete SawCapable of sawing the ends of a cylindrical specimen perpendicular to the axis and parallel to each other. 5.2. BalanceA scale or balance having a capacity of 20 kg (44 lb) and an accurateness of 0.1 percent over its range. 5.3. CaliperComparator or other suit
11、able device to measure the specimen length to the nearest 0.1 mm (0.004 in.). 5.4. Calibration SpecimenA calibration specimen with a known coefficient of thermal expansion shall be used to determine the correction factor of the equipment. The specimen shall be composed of a material that is essentia
12、lly linearly elastic, noncorroding, nonoxidizing, nonporous, and nonmagnetic, and it shall have a known thermal coefficient of expansion not to exceed 20 micro strain/C determined over the temperature range of 10 to 50C (50 to 122F) (see Note 1). Option 1: An ISO 9001 or equivalent laboratory should
13、 determine the CTE of the calibration specimen according to ASTM E228 or ASTM E289 within the temperature range of 10 to 50C (50 to 122F) and provide a certificate of the CTE value (see Note 2). Option 2: Manufacturer determines the CTE of the calibration specimen determined from a properly calibrat
14、ed CTE device meeting T 336 requirements . The CTE device used to determine the CTE of calibration specimens must be calibrated and verified using specimens that have previously been determined following Option 1.The CTE value and date tested shall be marked on the calibration specimen. The diameter
15、 of the calibration specimen should be large enough to firmly rest on the semispherical support buttons of the frame described in Section 5.7 and the length should be 177.8 2.5 mm (7.0 0.1 in.) (see Note 3). Note 1Grade 304 stainless steel, titanium and nickel are suitable materials. Note 2Testing o
16、f a full-height specimen is preferred. If coupons are used to determine the CTE of the calibration specimen, care must be taken to ensure that the longitudinal direction of the coupon is in the same direction as the calibration specimen it represents. The coupons shall be obtained adjacent to the lo
17、cation where the full-height specimen was obtained. Note 3Different-length concrete specimens can be tested provided the frame is recalibrated and verified with specimens with lengths that are 2.54 mm (0.1 in.) of the concrete specimen to be tested. 5.5. Length Change Measurement DeviceThe sample le
18、ngth change shall be measured using any suitable apparatus that has sufficient resolution and gives reproducible results. In this standard, the use of a linear variable differential transducer (LVDT) is described. The LVDT with excitation source and digital readout shall have a minimum resolution of
19、 0.000125 mm (0.000005 in.) and a range suitable for the test. The semi-spherical contact tip (at the point of contact between the measuring device and the specimen) must be firmly attached to the length change measuring device to prevent loosening during a test (see Note 4). Note 4Submersible and n
20、onsubmersible LVDTs are suitable. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 336-3 AASHTO 5.6. Support FrameA rigid support frame for the specimen to be used during length change measurement
21、 (Note 5). The frame shall be designed to have minimal influence on the length change measurements obtained during the test and should support the specimen such that the specimen is allowed to freely adjust to any change in temperature. Any specimen measuring frame should be constructed with the fol
22、lowing features: 5.6.1. The frame should be made of a noncorroding material or be protected against corrosion, as necessary (see Note 5). Note 5Frames may be designed to accommodate different-length concrete specimens. Frames shall be calibrated and verified with specimens 2.54 mm (0.1 in) of the te
23、st specimen length. Figure X1.1 shows a schematic of a suitable measuring frame. 5.7. Temperature Measuring DeviceSubmersible temperature measuring device(s) with a resolution of 0.1C (0.2F) and an accuracy of 0.2C (0.4F), verified with a NIST traceable thermometer. 5.8. Verification SpecimenA speci
24、men, other than the calibration specimen with a known CTE used to verify that the equipment is operating properly. The specimen should be composed of a material that is essentially linearly elastic, noncorroding, nonoxidizing, nonporous, and nonmagnetic, and it should have a known thermal coefficien
25、t at least 3 106/C different from the calibration specimen. Option 1: An ISO 9001 or equivalent accredited laboratory should determine the CTE of the calibration specimen according to ASTM E228 or ASTM E289 within the temperature range of 10 to 50C and provide a certificate of the CTE value (see Not
26、e 1). Option 2: Manufacturer determines the CTE of the verification specimen determined on a properly calibrated CTE device. The CTE device used to determine the CTE of verification specimens must be calibrated and verified using specimens that have previously been determined following the procedure
27、s in Option 1.The diameter of the verification specimen shall be large enough to firmly rest on the semispherical support buttons of the frame described in Section 5.7, and the length should be 177.8 2.54 mm (7.0 0.1 in.) 5.9. Water BathA controlled-temperature water bath with a temperature range of
28、 10 to 50C (50 to 122F) and a resolution of 0.1C (0.2F). 5.10. Water Curing Tank A tank made of noncorroding materials with automatic control of water temperature at 23.0 2.0C (73 4F). 6. TEST SPECIMENS 6.1. Test specimens shall consist of drilled cores with a 100-mm (4-in.) nominal diameter sampled
29、 from the concrete structure being evaluated or cast cylinders with 100-mm (4-in.) nominal diameter. Cores shall be obtained in accordance with T 24M/T 24. Cylinders shall be cast in accordance with T 23 or R 39. Both ends of the specimens shall be sawn perpendicular to the axis to achieve a length
30、of 177.8 2.54 mm (7.0 0.1 in.). The sawn ends shall be flat and parallel, according to T 22. Two specimens shall be tested per mixture. 6.2. Specimen ConditioningThe specimens shall be conditioned by submersion in limewater in a water storage tank at 23 2C (73 4F) until two successive weighings of t
31、he surface-dried sample at intervals of 24 h show an increase in weight of less than 0.5 percent. A surface-dried sample is obtained by removing the surface moisture with a towel. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a vio
32、lation of applicable law.TS-3c T 336-4 AASHTO 7. PROCEDURE 7.1. Calibration and Verification Procedure: 7.1.1. LVDT CalibrationThe LVDT and associated data acquisition system shall be calibrated according to the manufacturers instructions a minimum of every 6 months or in circumstances where the CTE
33、 results are inconsistent. The correction factor shall be determined after the LVDT has been calibrated using the procedure outlined in Section 7.1.2. 7.1.2. Determination of the Correction FactorThe test procedure described in Section 7.2 is used to determine a correction factor to account for expa
34、nsion of the measuring apparatus during the test. A calibration specimen with a known coefficient of thermal expansion shall be used. The calibration specimen shall be large enough to firmly rest on the semispherical support buttons of the frame described in Section 5.7 and the length should be 177.
35、8 2.54 mm (7.0 0.1 in.) so that no adjustment of the frame is necessary between calibration and testing (see Note 3). 7.1.2.1. Calculation of the Correction Factor: 7.1.2.1.1. Assuming that the length change of the apparatus varies linearly with temperature, the correction factor Cf is defined as: f
36、 f csC LL T= (1) where: Lf= length change of the measuring apparatus during temperature change, mm (see Equation 2); Lcs= measured length of calibration specimen at room temperature, mm; and T = measured temperature change, C (increase = positive, decrease = negative). f amL LL = (2) where: La= actu
37、al length change of calibration specimen during temperature change, mm (see Equation 3); and Lm= measured length change of calibration specimen during temperature change, mm (increase = positive, decrease = negative). a cs cLL T = (3) where: c= CTE of calibration specimen, C (known). 7.1.3. Equipmen
38、t VerificationThe CTE set-up shall be verified at least once a month by testing a verification specimen of known CTE other than the calibration specimen, according to the procedure in Section 7.2. If the results of the verification test differ by more than 0.3 106/C of the certified value, the sourc
39、e of error must be corrected and the correction factor shall be determined again using the procedure outlined in Section 7.1.2. 7.1.4. Water Bath VerificationThe water temperature should be verified every six months with an accuracy of 0.2C (0.4F), using a NISTtraceable thermometer or in circumstanc
40、es where the equipment verification CTE results are inconsistent. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 336-5 AASHTO 7.2. Testing Procedure: 7.2.1. Remove the specimen from the water cu
41、ring tank and measure its length at room temperature to the nearest 0.1 mm (0.004 in.). After measuring the length, place the specimen in the support frame, making sure that the lower end of the specimen is firmly seated against the support buttons and that the LVDT tip is seated against the upper e
42、nd of the specimen (see Note 7). With the specimen in the frame at room temperature, adjust the body of the LVDT so that the core of the LVDT is located at its midpoint or electrical zero reading. Note 6The LVDT travel during the test should remain well within the calibrated range to ensure accurate
43、 results. 7.2.2. Place the support frame and specimen, with the LVDT attached, in the water bath which is filled with tap water. The height of the water shall remain constant throughout the test and be set to the same level as that used to calibrate the frame. Set the temperature of the water bath t
44、o 10 1C (50 2F) (see Note 7).When the bath reaches this temperature, allow the bath to remain at this temperature until thermal equilibrium of the specimen has been reached, as indicated by consistent readings of the LVDT taken every 10 min over a 1/2-h period. The difference between the maximum and
45、 minimum readings shall be less than or equal to 0.00025 mm (0.00001 in.). If this criterion is not met, additional 10-min readings shall be obtained until four consecutive 10-min readings are within the range of 0.00025 mm (0.00001 in.). Note 7The test can start at either 10 C or 50 C (50 F or 122
46、F) without affecting the test results. However, it was found that starting at 50 C (122 F) may reduce the number of segments to complete the test. 7.2.3. Record the temperature readings from the sensor(s) to the nearest 0.1C (0.2F). Record the LVDT reading to the nearest 0.000125 mm (0.000005 in.).
47、7.2.4. Set the temperature of the water bath to 50 1C (122 2F). Once the bath has reached 50 1C (122 2F), allow the bath to remain at this temperature until thermal equilibrium of the specimen has been reached, as indicated by consistent readings of the LVDT within the range of 0.00025 mm (0.00001 i
48、n.) taken every 10 min over a 1/2-h period for a total of four readings. The difference between the maximum and minimum readings shall be less than or equal to 0.00025 mm (0.00001 in.). If this criterion is not met, additional 10-min readings shall be obtained until four consecutive 10-min readings
49、are within the range of 0.00025 mm (0.00001 in.). 7.2.5. Record the temperature readings from the sensor(s) to the nearest 0.1C (0.2F). Record the LVDT reading to the nearest 0.000125 mm (0.000005 in.). 7.2.6. Set the temperature of the water bath to 10 1C (50 2F). When the bath reaches this temperature, allow the bath to remain at this temperature until thermal equilibrium of the specimen has been reached, as indicated by consistent read
