1、Standard Method of Test for Pore Index for Carbonate Coarse Aggregate AASHTO Designation: TP 120-161Release: Group 3 (August 2016) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-1c TP 120-1 AASHTO Standard Method
2、of Test for Pore Index for Carbonate Coarse Aggregate AASHTO Designation: TP 120-161Release: Group 3 (August 2016) 1. SCOPE1.1. This test method covers the determination of the pore index values for carbonate (limestone anddolomite) coarse aggregate for Portland Cement (PC) Concrete.1.2. The values
3、stated in SI units are to be regarded as the standard.1.3. This standard does not purport to address all of the safety concerns associated with its use. It isthe responsibility of the user of this procedure to establish appropriate safety and health practicesand to determine the applicability of reg
4、ulatory limitations prior to its use.2. REFERENCED DOCUMENTS2.1. AASHTO Standards: M 231, Weighing Devices Used in the Testing of Materials T 27, Sieve Analysis of Fine and Coarse Aggregates3.3.1. SUMMARY OF TEST METHODThe method uses water pressure at 240 kPa (35 psi) to force water into the aggreg
5、ate pores. A measurement is made of the volume of water that is forced into the aggregate during a period between 1 min and 15 min after application of the pressure.4. SIGNIFICANCE AND USE4.1. The pore index test is used to quickly assess the pore system of carbonate coarse aggregates andidentify po
6、tential freeze-thaw durability issues for use in PC Concrete.4.2. Carbonate aggregates with secondary pore index values of 20 or below have a pore system that isgenerally indicative of an aggregate that will be resistant to freeze-thaw damage in air entrainedPC Concrete. Higher secondary pore index
7、values indicate a larger pore system that is generallyindicative of an aggregate susceptible to freeze- thaw damage in air entrained PC Concrete(Reference 13.1.).5. APPARATUS5.1. Iowa Pore Index UnitA measuring device consisting of a Pressure Chamber, chamber pressurecontrol device, chamber pressure
8、 measurement device, and a chamber volume measurementdevice. See Figure 1. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c TP 120-2 AASHTO 5.2. Pressure ChamberA metal or plastic container of suffi
9、cient volume to hold 1000 g to 4500 g of normal weight carbonate aggregate. The container must be corrosion resistant and capable of withstanding 240 kPa (35 psi) pressure. The top plate shall have a vent such that the air can be forced out of the chamber as it is filled with water. The container sh
10、all have an inlet at or near the base through which water is supplied. Note 1One such instrument that has been used successfully for this testing is shown in Figure 1. Note 2A clear pressure chamber will allow the operator to visually determine when all the entrapped air bubbles have been removed pr
11、ior to pressurizing. 5.3. Chamber Pressure Control DeviceThe chamber pressure control device shall be capable of applying and controlling pressure to within 240 3 kPa (35 0.5 psi). The pressure shall be applied such that 240 3 kPa (35 0.5 psi) is achieved within 6 s for the chamber with water only a
12、nd within 12 s for the chamber and the aggregate under test. The device may consist of a pneumatic pressure regulator, or any other device capable of applying and controlling pressures to the required tolerances. 5.4. Chamber Pressure Measurement DeviceThe chamber pressure measurement device shall b
13、e capable of measuring the pressures to the tolerances given in Section 5.2. It may be a pressure manometer, electronic pressure transducer, or any other device capable of measuring pressures to the stated tolerances. 5.5. Chamber Volume Measurement DeviceThe chamber volume measurement device shall
14、be capable of measuring volume change to a precision of at least 0.1 percent of the sample volume for the primary reading and 0.05 percent of the sample volume for the secondary reading. 5.6. TimerA timing device that can be read or can record elapsed time to the nearest second. 5.7. BalanceThe bala
15、nce shall have a capacity of 5000 g and comply with M 231 class G 2. Figure 1Iowa Pore Index Unit 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c TP 120-3 AASHTO 6. STANDARDIZATION 6.1. The volume
16、change in the chamber when pressurized must be determined and used to correct the test readings. This should be done at least once a day prior to performing a test. 6.2. Fill the chamber with room temperature water. Ensure that all entrapped air is removed from the chamber. 6.3. Apply the 240 kPa (3
17、5 psi) pressure. Record the volume change at 60 s and 15 min. 6.4. The results from the standardization test should not vary by more than 10 percent from the previous standardization results. 7. PREPARATION OF TEST SPECIMEN 7.1. Sieve the sample over the 19.0 mm (3/4in.) sieve and the 12.5 mm (1/2in
18、.) sieve. Obtain a sufficient amount of material retained on the 12.5 mm ( in.) sieve to provide for enough oven dried material for the test. Note 3Smaller sizes of aggregate have been used in the test. The pore index results are generally lower when aggregates smaller than the 12.5 mm (1/2in.) are
19、used (Section 13.2). 7.2. Wash the material and dry it in an oven or a suitable pan or vessel to constant mass at a temperature of 110 5C (230 9F). Allow it to cool to room temperature. 8. PROCEDURE 8.1. Weigh out the desired test sample size and record the mass to the nearest 0.5 g. 8.2. Place the
20、test sample in the pressure chamber and close and seal the lid. 8.3. Start the timer and begin filling the chamber with room temperature water. Make sure that all large entrapped air bubbles are removed by rocking the chamber or tapping the sides of the chamber. Some aggregates will release small ai
21、r bubbles during the filling process. 8.4. Initialize or zero the volume measuring device. 8.5. Apply the pressure at 90 5 s from the time the chamber filling began. 8.6. Check for any water or air leaks. 8.7. Record the water volume change at 60 s and 15 min from the time the pressure was applied.
22、Note 4Recording volume readings at more frequent intervals or for more than 15 min may provide additional useful information about the pore structure. 8.8. After the final reading, release the pressure and allow the sample to drain. 9. CALCULATIONS 9.1. The pore index values are calculated as follow
23、s: 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c TP 120-4 AASHTO ( )1 1019000 Primary Pore Index Value V Vs VW= (1) ( )15 15 1 119000 Secondary Pore Index Value V Vs Vs VW= (2) where: W1 = Initia
24、l sample mass, g; VS1 = Water volume reading at 60 s from the standardization test, mL; VS15 = Water volume reading at 15 min from the standardization test, mL; V0 = Initial water volume reading, mL; V1 = Water volume reading at 60 s, mL; and V15 = Water volume reading at 15 min, mL. 10. REPORT10.1.
25、 Report the mass of the dry test sample to the nearest 0.5 g.10.2. Report the 60-s and 15-min standardization readings.10.3. Report the primary and secondary pore index values to the nearest whole number.11. PRECISION AND BIAS11.1. PrecisionNo precision has been established for this method.11.2. Bia
26、sNo bias has been established for this method.12. KEYWORDS12.1. Aggregate durability; aggregate pores; concrete freeze-thaw; pore index.13. REFERENCES13.1. Myers, J. D., and W. Dubberke. Iowa Pore Index Test. Interim Report ML80-02. Iowa Departmentof Transportation, Ames, IA, 1980.13.2. Davis, C. P.
27、 Influence of Particle Size and Specimen Preparation on the Iowa Pore Index. MastersThesis. Missouri University of Science and Technology, Rolla, MO, 2011.1This provisional standard was first published in 2016. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
