1、Standard Method of Test for Determination of Cement Content in Cement-Treated Aggregate by the Method of Titration AASHTO Designation: T 211-90 (2012) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-1c T 211-1 AASH
2、TO Standard Method of Test for Determination of Cement Content in Cement-Treated Aggregate by the Method of Titration AASHTO Designation: T 211-90 (2012) 1. SCOPE 1.1. This method of test covers a procedure for determining cement content based upon the continuous neutralization of an aqueous solutio
3、n from the cement-treated aggregate specimen for a specified time period. This is accomplished by adding sufficient acid to just neutralize the OHion that is continuously being liberated during the hydration of the cement. The amount of acid used is directly proportional to the cement content of the
4、 treated base sample. 1.2. The following applies to all specified limits in this standard: For the purposes of determining conformance with these specifications, an observed value or a calculated value shall be rounded off “to the nearest unit” in the last right-hand place of figures used in express
5、ing the limiting value, in accordance with ASTM E29. 1.3. The values stated in SI units are to be regarded as the standard. 1.4. Refer to R 16 for regulatory information for chemicals. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 231, Weighing Devices Used in the Testing of Materials R 16, Regul
6、atory Information for Chemicals Used in AASHTO Tests 2.2. ASTM Standard: E29, Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications 3. APPARATUS 3.1. titrating buret100-mL; or other device permitting slow, easily controlled addition of acid. 3.2. ot
7、her buret equipmentstand and clamp. 3.3. polyethylene containersfour 1.9-L (2-qt), wide-mouth (white). 3.4. plastic carboystwo 18.9-L (5-gal) plastic carboys equipped with siphons, neoprene or tygon tubing hose clamps, and any other equipment needed to contain acid working solution and water; do not
8、 substitute glass containers for the plastic carboys. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 211-2 AASHTO 3.5. A glass dropping bottle. 3.6. Four stainless steel stirring rods. 3.7. 9.5-
9、mm sieve, 305-mm (12-in.) diameter. 3.8. 37.5-mm sieve, 305-mm (12-in.) diameter. 3.9. A balance or scale conforming to the requirements of M 231, Class G 2, and Class G 5. 4. REAGENTS 4.1. Hydrochloric Acid (HCl) (Approximately 3 Normal)Pour approximately 11.4 L (3 gal) of water into an 18.9-L (5-g
10、al) plastic carboy. Pour the contents of two full standard 2.7-kg (6-lb) bottles of concentrated reagent-grade HCl in the carboy. Stir or mix the solution vigorously for about 1 min. Add tap water as necessary to bring the total volume of water and acid to 18.9 L (5 gal): then stir or mix the soluti
11、on vigorously for another minute. Allow the acid solution to stand overnight; then remix it once again prior to using. Remix the acid solution once a week during use and also before using if the acid solution has been in storage for more than one week. Note 1The operator mixing the acid solution is
12、required, for safety, to wear protective gloves, goggles, and aprons. 4.2. Phenolphthalein Indicator Solution (1-Percent Solution)Dissolve 5 g of phenolphthalein powder USP in 250 mL of ethanol. Dilute with 250 mL of distilled water. 5. DETERMINATION OF A STANDARD CURVE 5.1. Use the particular aggre
13、gate, cement, and water from the project. Normally only one point is needed to establish the standard curve and this point is determined from duplicate tests on specimens containing 5-percent cement. However, if a small sample of untreated aggregate in water shows a red color on adding a few drops o
14、f phenolphthalein solution, indicating the presence of water-soluble alkalis, then duplicate aggregate blank specimens should also be tested. 5.2. Determine a representative field moisture in percent for the cement-treated material from road moisture samples obtained after mixing. 5.3. Refer to Tabl
15、e 1 and select the mass of aggregate corresponding to the appropriate moisture content and 5 percent cement. This figure is the dry mass of untreated aggregate required to make a 5 percent calibration test specimen of 300 g. If the samples of untreated aggregate initially contain moisture, then adju
16、st the mass of aggregate plus water to conform to the tabular values. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 211-3 AASHTO Table 1Quantities of Materials for Calibration Specimens Contain
17、ing 5-Percent Cement Moisture Content, % Dry Mass of Aggregate, g Volume of Water, mL Mass of Cement, g 5 271 15 13.6 6 270 17 13.5 7 267 20 13.3 8 265 22 13.2 9 263 24 13.1 10 260 27 13.0 11 257 30 12.9 12 255 32 12.8 13 252 35 12.6 14 250 37 12.5 15 249 39 12.4 16 247 41 12.3 17 244 44 12.2 18 242
18、 46 12.1 19 240 48 12.0 20 238 50 11.9 5.4. From the project records determine the average percentage of untreated aggregate passing the 9.5-mm sieve. This percentage passing the 9.5-mm sieve along with the portion retained on the 9.5-mm sieve will be the proportion used for the calibration specimen
19、s. 5.5. Remove and waste any aggregate in the sample of untreated material retained on the 37.5-mm sieve and then separate the sample on the 9.5-mm sieve. Recombine for duplicate calibration test specimens with the aggregate mass found in Section 5.3, and with the 9.5-mm sieve proportions found in S
20、ection 5.4. 5.6. Pour the weighed aggregate and cement (cement weighed to 0.1 g) into the 1.9-L (2-qt) plastic container and dry-mix together thoroughly with a stainless steel stirring rod. 5.7. Add the amount of water specified in Table 1 and again mix thoroughly. 5.8. In order to correlate with th
21、e field testing operations, allow the mixture to stand in the covered plastic container for a period of time that corresponds to the time required to obtain a field-treated sample, transport it to the testing location, and prepare the 300 g test specimens. 5.9. Add 250 mL of tap water to each specim
22、en and start timer. 5.10. Add two droppers full (approximately 40 drops) of phenolphthalein solution to each container. The water solution will normally turn red due to the presence of cement. 5.11. Determine the mass of each plastic container, including its contents, to the nearest 0.5 g. 5.12. Ten
23、 min after the addition of water, start adding the 3 Normal hydrochloric acid with a titrating buret while stirring continuously. 5.12.1. The initial amount of acid to be added is based upon the planned cement content of the mix and is determined from Figure 1. 2015 by the American Association of St
24、ate Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 211-4 AASHTO Figure 1Constant Neutralization ProcedureHydrochloric Acid Starting Quantities 5.12.1.1. Example: Suppose the planned cement content for a given project is 3.5 percent. Ent
25、er the abscissa of the chart in Figure 1 at 3.5 percent and find the intersection with the upper diagonal line. Reading from the ordinate to the nearest milliliter, it is noted that 15 mL of HCl is required. Use the titrating buret to measure and add the 15 mL of acid to the specimen in the plastic
26、container. When the proper amount of acid is used, the red color in the solution will disappear. 5.12.2. When the red color starts to reappear after the initial introduction of acid, use the buret to make a second addition of acid in the amount (mL) indicated by the lower diagonal line (at the plann
27、ed cement content) of the chart in Figure 1. 5.13. After the first two additions of acid, make subsequent additions at random as soon as the red color reappears, using only the minimum amounts necessary to cause the color to just disappear and maintain a neutral solution. This requires constant atte
28、ntion by the operator. 5.14. Besides the stirring accomplished during each introduction of acid, additional light stirring (for about 3 s) should be performed every minute, with every fifth minute being devoted to deep stirring (for about 6 s), whether or not color is present. 5.15. Continue this pr
29、ocedure of adding acid and stirring until 1 h after the initial addition of water to the specimen. Then reweigh the plastic container and contents to the nearest 0.5 g. 5.16. From the difference between the initial and final gross test specimen masses, calculate and record the total mass of hydrochl
30、oric acid used to neutralize the solution. 242220181614121086420InitialAddition ofAcidPercent Cement0 1.0 2.0 3.0 4.0 5.0 6.03NHydrochloricAcid,mL2ndAddition ofAcid 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of appli
31、cable law.TS-1c T 211-5 AASHTO 5.17. Plot the grams of acid used against percent cement for both duplicate 5-percent cement specimens (also aggregate blank specimens if tested). Draw a straight line from the origin of the chart (or the average of the duplicate blanks) to the average of the tests on
32、the 5-percent specimens. This is the standard curve for determining the cement content of field mixed cement-treated specimens. 6. TEST PROCEDURE FOR FIELD SAMPLES 6.1. Secure one to four 3-kg field samples of the cement-treated aggregate. Remove and waste any aggregate retained on the 37.5-mm sieve
33、. Separate sample on the 9.5-mm sieve and determine the proportion passing the 9.5-mm sieve on the basis of total sample mass including retained 37.5-mm material. 6.2. Recombine the retained and passing 9.5-mm portions for the 300-g test specimens in their “As received” proportions, place each speci
34、men in a separate 1.9-L (2-qt) plastic container, and line the containers up along the front of the work bench. Follow steps in Sections 5.9 through 5.16. 6.3. Using the resulting mass of hydrochloric acid, determine the percentage of cement in the specimens from the standard curve established in Se
35、ction 5.17. 6.4. Report the cement content to the nearest 0.1 percent. 7. PRECAUTIONS 7.1. This test should not be performed by persons subject to color blindness. 7.2. It is very important that the operator vigilantly maintain a neutral solution by repeatedly adding acid as soon as the pink color r
36、eappears. 7.3. After the first two additions of acid, use only the amount necessary to just eliminate the red color. Excess acid may attack the aggregates, particularly in the later phases when the amount of hydration products from the cement remaining in the mixture may be low. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
