1、Standard Method of Test for Quantifying Calcium Oxychloride Amounts in Cement Pastes Exposed to Deicing Salts AASHTO Designation: T 365-17 Technical Section: 3c, Hardened Concrete Release: Group 1 (April 2017) American Association of State Highway and Transportation Officials 444 North Capitol Stree
2、t N.W., Suite 249 Washington, D.C. 20001 TS-3c T 365-1 AASHTO Standard Method of Test for Quantifying Calcium Oxychloride Amounts in Cement Pastes Exposed to Deicing Salts AASHTO Designation: T 365-17 Technical Section: 3c, Hardened Concrete Release: Group 1 (April 2017) 1. SCOPE 1.1. This test meth
3、od covers the procedure for quantitative determination of calcium oxychloride amounts formed in cement pastes exposed to deicing salts. 1.2. The values stated in SI units are to be regarded as the standard. 1.3. This standard does not purport to address all of the safety problems, if any, associated
4、 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 Standard M 231, Weighing Devices Used in the Testing of Materials 2.2.
5、 ASTM Standards: C305, Standard Practice for Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic Consistency D1193, Standard Specification for Reagent Water E11-09, Standard Specification Wire-Cloth Sieves for Testing Purposes E1269, Standard Test Method for Determining Specific Heat
6、 Capacity by Differential Scanning Calorimetry 2.3. Other Standard: Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference Materials, Committee on Analytical Reagents of the American Chemical Society 3. SUMMARY OF TEST METHOD 3.1. This test method covers the proce
7、dure for quantitative determination of calcium oxychloride amounts formed in cement pastes exposed to deicing salts. 3.2. Hydrated cement paste is ground to a fineness sufficient to pass through a No. 200 (75-m) sieve. The ground powder is exposed to a 20 percent (by mass) calcium chloride salt solu
8、tion, thoroughly mixed using a powder solution ratio of 1:1, and then placed and tested in a Low- 2017 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 365-2 AASHTO Temperature Differential Scanning Ca
9、lorimetry (DSC) machine. The heat required to change the sample temperature is recorded as a function of temperature throughout the duration of the test. As the temperature increases, the formed calcium oxychloride undergoes a phase change around 30C; the amount of calcium oxychloride can be quantif
10、ied by comparing the heat released with the heat released from the phase change of pure calcium oxychloride. 3.3. This specific standard is written for the reaction between a ground hydrated cement paste and a 20 percent by mass calcium chloride solution; however, the same general principle is appli
11、cable for blends of calcium chloride and sodium chloride salt solutions and solutions of different strengths by mass. These details are discussed in the reference listed in Section 12.1. 4. SIGNIFICANCE AND USE 4.1. This test method is used for determining the amount of calcium oxychloride formed in
12、 a cementitious paste exposed to a deicing salt or deicing salt mixture. This test method is suitable for evaluating the effects of changes in cement composition, type and dosage of supplementary cementitious materials, water-to-cement ratio, curing time, salt solution composition, and solution stre
13、ngth on the amount of calcium oxychloride formed the paste. 4.2. The actual amount of calcium oxychloride that forms in concretes in the field and the subsequent damage that results depends on several other variables including environment, construction practices, air content, etc. This test method d
14、oes not predict the effect of these factors; however, it predicts the maximum amount of calcium oxychloride that can form in different paste or concrete compositions and therefore is useful from a performance specification point of view to design mixes that will be free from calcium oxychloride rela
15、ted damage. 4.3. Although this test method accurately predicts the amount of calcium oxychloride that can form and potential mitigation strategies that can be used to reduce this amount, implementation of the mitigation strategies must be done with caution. As an example, replacing more than 60 perc
16、ent of the cement with supplementary cementitious materials reduces the amount of calcium oxychloride to almost zero; however, such mixtures may potentially have lower early strengths and could have poor corrosion resistance. 4.4. The amount of calcium hydroxide in the pastes as determined by thermo
17、gravimetric analysis is a good indicator of the amount of calcium oxychloride that can form in these pastes. The relation between calcium hydroxide and calcium oxychloride amounts is discussed in detail in the references listed in Sections 12.1 and 12.2. 5. APPARATUS 5.1. Cylindrical MoldsPlastic cy
18、lindrical molds with a diameter of 1.5 in. and a height of 2.0 in. in which cement paste samples can be cast. 5.2. Grinding MachineA grinding machine or lathe that can be used to grind the paste sample to a fine powder. 5.3. SieveA No. 200 sieve, conforming to the requirements of ASTM E11-09 to siev
19、e out coarse paste particles. 5.4. BalanceAnalytical balance, Class A, conforming to the requirements of M 231 to weigh the powder and the solution. The balance must have a precision of 0.1 mg. 5.5. MicropipetTo add the liquid to the powder. The micropipet must have a precision of 0.1 L. 2017 by the
20、 American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 365-3 AASHTO 5.6. ContainersSuch as high-volume stainless steel pans, rubber O-rings, and lids which are inert to the sample materials and whose shape and str
21、uctural integrity can withstand temperatures within the DSC machine. 5.7. Encapsulation DeviceTo seal the high-volume stainless steel pans to prevent spillage during the DSC test. 5.8. DSC Test ChamberIn accordance with ASTM E1269. 6. SAMPLE PREPARATION 6.1. ReagentsReagent grade chemicals shall be
22、used in all tests. Unless otherwise indicated, all reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society. For this standard, reagent grade calcium chloride (CaCl2) is used to prepare salt solutions representative of salt solutions used
23、in the field. 6.2. WaterUnless otherwise indicated, water used shall be Type II reagent water in accordance with ASTM D1193. 6.3. Salt Solution PreparationDissolve 1 g of salt solution in 4 g water. Mix in small plastic cylinders (example size: diameter of 1.5 in. and a height of 2.0 in.). Seal cont
24、ainer and store at a temperature of 23C. Solution should be used for a maximum of 7 days after preparation. If any precipitates are noted in the solution at any time it must be discarded and fresh solution must be prepared. Note 1The dissolution of CaCl2in water is highly exothermic, so precautions
25、must be taken if large amounts of solution are to be prepared (over 30 g). Table 1Solution Masses Solution CaCl2(g) Water (g) Solution (g) 20 percent solution 1 4 5 6.4. Cement Paste PreparationPrepare a hydrated cement paste sample in accordance with ASTM C305. Cast sample in a small plastic cylind
26、er with a diameter of 1.5 in. and a height of 2.0 in. Seal containers and cure for 3 days at a temperature of 23C followed by 25 days at a temperature of 50C. Example mix proportions for a sample with water-to-cement ratio (w/c) 0.36 are presented in Table 2. At the end of the curing period, cut ope
27、n the plastic mold and the remove the sample from the mold. Note 2The curing procedure is used to ensure a high degree of hydration; however, the test method does not depend on the curing procedure. Table 2Mixture Proportions Paste w/c Cement (g) Water (g) Paste 1 0.36 658 237 6.5. Sample GrindingCr
28、ush 100 g of the material (hydrated cement paste) using either a grinding machine or mortar and pestle. Pass the ground material through a No. 200 sieve. Crush or grind the portion retained on the sieve, by means that will not contaminate the sample, until substantially all of the material passes th
29、rough the sieve. Combine all portions of the original 100 g material. 2017 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 365-4 AASHTO 7. TESTING PROCEDURE 7.1. Weigh 10 0.5 mg of ground powder in a
30、DSC high-volume stainless steel pan. 7.2. Add 10 0.5 mg of salt solution with micropipet to the powder in the pan. It is important to ensure that the liquid and solid masses are exactly the same to ensure a 1:1 liquid to solid ratio. The total mass of the contents inside the pan should be 20 1 mg. 7
31、.3. Mix contents well so that all powder is thoroughly wetted. 7.4. Hermetically seal lid containing rubber O-ring to pan using encapsulation device. 7.5. Place pan containing ground powder-salt solution mixture in DSC cell. 7.6. Expose pan to the following temperature cycle: 7.6.1. Equilibrate pan
32、at 25C for at least 50 min but not more than 60 min. 7.6.2. Cool sample to 90C at a rate of 3C/min. 7.6.3. Expose sample to low temperature loop, cycling from 90C to 70C to 90C at a rate of 3C/min. 7.6.4. Heat sample to 50C at a rate of 0.25C/min. 8. CALCULATION AND INTERPRETATION OF RESULTS 8.1. Us
33、e the software provided alongside DSC instrument to evaluate the heat flow data recorded by the DSC machine. Integrate the heat flow versus temperature curve associated with the calcium oxychloride melting phase transition. Calculate the magnitude of the drop in the cumulative heat curve. The amount
34、 calcium oxychloride (normalized per 100 g of cementitious paste) is calculated using Equation 1: 100oxyoxyHML= (1) where: Moxy= mass in g of calcium oxychloride per 100 g of cementitious paste, g/100 g H = latent heat absorbed during calcium oxychloride phase transformation in the tested cement pas
35、te, J/g Loxy= specific latent heat associated with pure calcium oxychloride phase transformation, 186 J/g 8.2. Example CalculationThe heat absorbed because of calcium oxychloride formation is evaluated by integrating the heat flow versus time curve as shown in Figure 1. The cumulative heat is estima
36、ted by calculating the magnitude of the shift in cumulative heat slopes before and after the phase transformation (between points A and C) with respect to the midpoint of the phase change (point B). Points A, B, and C all lie on the same vertical line. 2017 by the American Association of State Highw
37、ay and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 365-5 AASHTO Figure 1Illustration of Heat Absorbed because of Calcium Oxychloride Formation 8.3. Calculation 1 in Figure 2 is performed by choosing a midpoint along the cumulative heat curve (pi
38、nk line labeled as Integral) as described above. This midpoint is an estimation of the temperature corresponding to a cumulative heat value close to 50 percent of the total enthalpy value of the phase change. This percentage can be calculated by dividing the drop between points X and Y by the drop b
39、etween points X and Z (Points X, Y, and Z in the figure below correspond to Points A, B, and C, respectively, in the figure above). A temperature of 24.99C corresponds to 48.1 percent completion for this particular heat accumulation curve. The latent heat absorbed during calcium oxychloride phase tr
40、ansformation in this case (H) is 55.9 J/g. Therefore, the mass of calcium oxychloride per 100 g of cementitious paste (Moxy) = 30.05 using Equation 1. Figure 2Calculation of Heat Absorbed because of Calcium Oxychloride Formation ABCHeat absorbedbecause ofcalciumoxychlorideformation20 30 40 501201401
41、60180Temperature (C)Cumulative Heat (J/gcm)Calculation 1XYZ20.32C544.9 J/g20.39C189.0 J/g24.99C515.9 J/g60 40 20 0 20 40 60 800.120.100.080.060.040.02200400Integral(J/g)HeatFlow(W/g)Exo Up Temperature (C) Universal V4 5A TA 2017 by the American Association of State Highway and Transportation Officia
42、ls.All rights reserved. Duplication is a violation of applicable law.TS-3c T 365-6 AASHTO 9. REPORT 9.1. Report the following, if known: 9.1.1. Cement Paste PropertiesCement and supplementary materials source and chemical composition, mixture proportions (water-to-cement ratio and supplementary ceme
43、ntitious materials replacement level), and sample curing procedure; 9.1.2. The kind of salt solution used and the strength of the salt solution; this only needs to be reported if other salt solutions apart from the standard 20 percent CaCl2salt solution are used; 9.1.3. The amount of calcium oxychlo
44、ride formed to the nearest 0.01 g (per 100 g cement paste). 10. PRECISION AND BIAS 10.1. Precision: 10.1.1. Single-Operator PrecisionThe single-operator coefficient of variation of a single test result has been found to be 5.64 percent. Therefore, the results of two properly conducted tests by the s
45、ame operator on the same cement paste at the same age are not expected to differ by more than 5.64 percent of their average. 10.1.2. Multilaboratory PrecisionNo data is currently available on experimental variation between multiple laboratories. 11. KEYWORDS 11.1. Calcium chloride; calcium oxychlori
46、de; deicing salt; differential scanning calorimeter. 12. REFERENCES 12.1. Suraneni, P., J. Monical, E. Unal, Y. Farnam, and W. J. Weiss. Calcium oxychloride formation potential in cementitious pastes exposed to blends of deicing salt. In ACI Materials Journal, DOI 10.14359/51689607. American Concret
47、e Institute, Farmington Hills, MI, May/June, 2017. 12.2. Suraneni, P., V. J. Azad, O. B. Isgor, and W. J. Weiss. Calcium oxychloride formation in pastes containing supplementary cementitious materials: thoughts on the role of cement and supplementary cementitious materials reactivity. In RILEM Techn
48、ical Letters, Vol. 1. ScienceDirect, Elsevier, Amsterdam, The Netherlands, 2016. Available online at https:/ 12.3. Farnam, Y., C. Villani, T. Washington, M. Spence, J. Jain, and W. J. Weiss. Performance of carbonated calcium silicate based cement pastes and mortars exposed to NaCl and MgCl2deicing s
49、alt. In Construction and Building Materials, Vol. 111. ScienceDirect, Elsevier, Amsterdam, The Netherlands, May 2016, pp. 6371. 12.4. Monical, J., E. Unal, T. Barrett, Y. Farnam, and W. J. Weiss. Reducing joint damage in concrete pavements: quantifying calcium oxychloride formation for concrete made using portland cement, portland limestone cement
