1、Standard Method of Test for Potential Alkali Reactivity of Aggregates and Effectiveness of ASR Mitigation Measures (Miniature Concrete Prism Test, MCPT) AASHTO Designation: TP 110-141American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washingto
2、n, D.C. 20001 TS-3c TP 110-1 AASHTO Standard Method of Test for Potential Alkali Reactivity of Aggregates and Effectiveness of ASR Mitigation Measures (Miniature Concrete Prism Test, MCPT) AASHTO Designation: TP 110-1411. SCOPE 1.1. This test method allows detection of the potential for deleterious
3、alkali-silica reaction of aggregate in miniature concrete prisms within 56 days (8 weeks) for most of the aggregates. An additional 28 days (4 weeks) may be necessary in the case of low/slow reacting aggregates to assess their potential reactivity. To assess the effectiveness of mitigation measures
4、of SCMs (supplementary cementitious materials, such as fly ash, slag, silica fume, and others); the test method is conducted for 56 days. 1.2. The values stated in SI units are to be regarded as standard. The values in inch-pound units are shown in parentheses, and are for informational purposes onl
5、y. 1.3. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the
6、 applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 85, Portland Cement M 92, Wire-Cloth Sieves for Testing Purposes M 201, Mixing Rooms, Moist Cabinets, Moist Rooms, and Water Storage Tanks Used in the Testing of Hydraulic Cements and Concretes M
7、210M/M 210, Use of Apparatus for the Determination of Length Change of Hardened Cement Paste, Mortar, and Concrete R 16, Regulatory Information for Chemicals Used in AASHTO Tests T 19M/T 19, Bulk Density (“Unit Weight”) and Voids in Aggregate T 303, Accelerated Detection of Potentially Deleterious E
8、xpansion of Mortar Bars Due to Alkali-Silica Reaction 2.2. ASTM Standards: C 143/C 143M, Standard Test Method for Slump of Hydraulic-Cement Concrete C 157/C 157M, Standard Test Method for Length Change of Hardened Hydraulic-Cement Mortar and Concrete C 192/C 192M, Standard Practice for Making and Cu
9、ring Concrete Test Specimens in the Laboratory C 295, Standard Guide for Petrographic Examination of Aggregates for Concrete 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c TP 110-2 AASHTO C 490, S
10、tandard Practice for Use of Apparatus for the Determination of Length Change of Hardened Cement Paste, Mortar, and Concrete C 511, Standard Specification for Mixing Rooms, Moist Cabinets, Moist Rooms, and Water Storage Tanks Used in the Testing of Hydraulic Cements and Concretes C 702, Standard Prac
11、tice for Reducing Samples of Aggregate to Testing Size C 778, Standard Specification for Standard Sand C 1260, Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method) C 1293, Standard Test Method for Determination of Length Change of Concrete Due to Alkali-Silica React
12、ion D 75 Standard Practice for Sampling Aggregates D 1193, Standard Specification for Reagent Water 3. SIGNIFICANCE AND USE 3.1. Alkali-silica reaction (ASR) is a chemical reaction between certain forms of reactive silica present in aggregates and alkali hydroxides present in the concrete pore solut
13、ion. The alkali ions (Na+and K+) are primarily derived from portland cement, although other sources can potentially elevate their concentration in the pore solution. 3.2. This test method is intended to evaluate the potential of an aggregate (fine and coarse) to expand deleteriously due to any form
14、of alkali-silica reactivity. A companion nonreactive aggregate should be used with a reactive aggregate in question. Also, this test method is intended to assess the effectiveness of various mitigation measures. 3.3. When selecting a sample or deciding on the number of samples for test, it is import
15、ant to recognize the variability in lithology of material from a given source, whether a deposit of sand, gravel, or a rock formation of any origin. For specific advice, see ASTM C 295. 3.4. MCPT was developed as an alternative to the existing standard test methods such as ASTM C 1260 and ASTM C 129
16、3 to evaluate aggregate reactivity. This test method was developed with some modifications to standard test methods T 303 (ASTM C 1260) and ASTM C 1293. When evaluating coarse aggregate reactivity, MCPT has the advantage of not requiring the coarse aggregate to be crushed into smaller (sand-sized) p
17、articles, as typically required in ASTM C 1260 Also, the MCPT method yields test results in 8 weeks to characterize the aggregate reactivity, which is much shorter than the test duration required in ASTM C 1293. 3.5. The total alkali content of the cement used in this test method should have a Na2Oe
18、q. content of 0.90 0.10 percent. 3.6. For the vast majority of the aggregates that are either nonreactive or moderate to highly reactive, this test characterizes the aggregate reactivity in 8 weeks. For some specific aggregates that have a tendency to exhibit low/slow reactivity, an additional 4 wee
19、ks of testing is required. For the purpose of providing guidance on aggregate reactivity characterization, the following general guidelines are used in classifying the aggregate: 3.6.1. Very highly/highly reactive aggregates are considered as those aggregates which, when present in concrete with typ
20、ical alkali loading (3 to 5 lb/yd3), exhibit incipient signs of ASR distress in the field, typically at an age less than 5 years. 3.6.2. Moderate reactive aggregates are considered as those aggregates which, when present in concrete with typical alkali loading (3 to 5 lb/yd3), exhibit incipient sign
21、s of ASR distress in the field, typically at an age between 5 and 10 years. 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c TP 110-3 AASHTO 3.6.3. Low/slow reactive aggregates are considered as tho
22、se aggregates which, when present in concrete with typical alkali loading (3 to 5 lb/yd3), exhibit incipient signs of ASR distress in the field, typically at an age beyond 10 years. 3.7. Results of tests conducted as described herein should form a part of the basis for a decision as to whether preca
23、utions should be taken against excessive expansion due to alkali-silica reaction. This decision should be made before a particular aggregate is used in concrete construction. 3.8. The basic intent of this test method is to develop information on a particular aggregate at a specific alkali level of 5
24、.25 kg/m3(8.85 lb/yd3). It has been found that this high alkali level is required to detect the effects of certain deleteriously reactive aggregates. 3.9. When the expansions in this test method are greater than the limit (0.040 percent) shown in Table 1, the aggregate is potentially alkali-reactive
25、. An additional 28 days (4 weeks) may be necessary in the case of low/slow reacting aggregates (percent expansion between 0.031 and 0.040 percent) to assess their potential reactivity based on rate of expansion. When the expansions are 0.030 percent, then the aggregate is considered nonreactive. Tab
26、le 1Proposed Criteria for Characterizing the Aggregate Reactivity in the MCPT Protocol Degree of Reactivity Expansion at 56 Days, % (8 Weeks) Average 2-Week Rate of Expansion from 8 to 12 WeeksaNonreactive 0.030 N/AbNonreactive 0.0310.040 0.010% per 2 weeks Low/slow reactive 0.0310.040 0.010% per 2
27、weeks Moderate reactive 0.0410.120 N/AbHighly reactive 0.1210.240 N/AbVery highly reactive 0.240 N/AbaExample calculation for averaged rate of expansion from 8 to 12 weeks: If the average expansions of the three prisms at 8, 10, and 12 weeks are 0.035 percent, 0.046 percent, and 0.059 percent, respe
28、ctively, then the average rate of expansion between 8 to 12 weeks is equal to (0.059 0.037)/2 = 0.012 percent per 2 weeks. bNot applicable. 3.10. The criteria to determine the effectiveness of the SCMs in mitigating ASR expansions are given in Table 2. Table 2Proposed Criteria for Characterizing Eff
29、ectiveness of ASR Mitigation Measures in MCPT Method Efficiency of Mitigation Expansion at 56 Days, % (8 Weeks) Effective 0.025 aRecommend retest with MCPT using a higher dosage of mitigation. 4. APPARATUS 4.1. The apparatus shall conform to M 210, except as follows: 4.1.1. MoldsThe molds, the assoc
30、iated items for molding test specimens, and the length comparator for measuring length change shall conform to the applicable requirements of ASTM C 157/C 157M and ASTM C 490 and shall have square cross sections of 50.0 0.7 mm (2.00 0.03 in.). 2014 by the American Association of State Highway and Tr
31、ansportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c TP 110-4 AASHTO 4.1.2. ContainersThe containers shall be of such a nature that the prisms can be totally immersed in either water or 1N NaOH solution. The containers shall be made of material that can with
32、stand prolonged exposure to 60C (140F) and must be resistant to a 1N NaOH solution. The containers must be so constructed that when used for storing specimens, the loss or gain of moisture is prevented by tight-fitting covers, by sealing, or both. The prisms in the solution must be placed and suppor
33、ted so that the solution has access to the entire surface of the bar; therefore, it should be ensured that the specimens do not touch the sides of the container or each other. Note 1Recommended ContainerThe NaOH solution will corrode glass or metal containers. Polypropylene or high-density plastic h
34、ave been found to be acceptable. Experience has shown that 12-qt airtight storage containers made of plastic (from IRIS USA) appear to be satisfactory for use in this test method. However, any such similar containers may be used, as long as it is ensured that the container and the lid provide an air
35、tight environment and do not let the soak solution evaporate in the course of the test method. The concrete prisms should be placed on top of spacer bars (5- to 10-mm plastic rods) at the bottom of the container to allow the test specimens to have free access to soak solution on all surfaces. 4.1.3.
36、 Oven or Water BathA thermostatically controlled oven or water bath capable of maintaining a temperature of 60.0 1.7C (140.0 3F). 4.1.4. Moist Room or ClosetThe moist closet or room shall conform to M 201. 5. REAGENTS 5.1. Sodium Hydroxide (NaOH)USP or technical grade may be used, provided the Na+an
37、d OHconcentrations are shown by chemical analysis to lie between 0.99N and 1.01N. 5.2. Purity of WaterUnless otherwise indicated, references to water shall be understood to mean reagent water conforming to Type IV of ASTM D 1193. 5.3. Sodium Hydroxide SolutionEach liter of solution shall contain 40.
38、0 g of NaOH dissolved in 900 mL of water, and shall be diluted with additional distilled or deionized water to obtain 1.0 L of solution. It should include sufficient test solution to ensure complete immersion of the prisms. A soak solution volume of 4.5 L, which is equal to twice the volume of the t
39、hree MCPT specimens, was found to be adequate in submerging the three test specimens in the 12-qt airtight container. Note 2Warning: Before using NaOH, review: (1) the safety precautions for using NaOH; (2) first aid for burns; and (3) the emergency response to spills, as described in the manufactur
40、ers Material Safety Data Sheet or other reliable safety literature. NaOH can cause very severe burns and injury to unprotected skin and eyes. Suitable personal protective equipment should always be used. These should include full-face shields, rubber aprons, and gloves impervious to NaOH. Gloves sho
41、uld be checked periodically for pinholes. 6. CONDITIONING 6.1. Maintain the temperature of the molding room and dry materials at not less than 20C (68F) and not more than 27.5C (81.5F). The temperature of the mixing water, and of the moist room, shall not vary from 23C (73.4F) by more than 1.7 C (3
42、F). 6.2. Maintain the relative humidity of the molding room at not less than 50 percent. The moist closet or room shall conform to ASTM C 511. 6.3. Maintain the storage oven or water bath in which the specimens are stored in the containers at a temperature of 60.0 1.7C (140.0 3F). 2014 by the Americ
43、an Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c TP 110-5 AASHTO 7. MATERIALS 7.1. CementUse a cement meeting the requirements for Type I portland cement as specified in M 85. The cement must have a total alkali cont
44、ent of 0.9 0.1 percent Na2Oeq.(Na2Oeq.is calculated as % Na2O +0.658 % K2O). Determine the total alkali content of the cement either by analysis or by obtaining a mill run certificate from the cement manufacturer. Add NaOH to the concrete mixing water so as to increase the alkali content of the mixt
45、ure, expressed as Na2O equivalent, to 1.25 percent by mass of cement. 7.2. Aggregates: 7.2.1. To evaluate the reactivity of a coarse aggregate, use a nonreactive fine aggregate. A nonreactive fine aggregate is defined as an aggregate that develops an expansion in the MCPT of less than 0.030 percent
46、at 56 days. Use a fine aggregate meeting T 27 with a fineness modulus of 2.6 0.3. Use the coarse aggregate gradation defined in Section 7.2.3. For the purposes of establishing the reactivity of coarse aggregate, unless a suitable local source of nonreactive fine aggregate is identified, graded Ottaw
47、a sand conforming to ASTM C 778 may be used as nonreactive sand. 7.2.2. To evaluate the reactivity of a fine aggregate, use a nonreactive coarse aggregate. A nonreactive coarse aggregate is defined as an aggregate that develops an expansion in the MCPT of less than 0.030 percent at 56 days. Use the
48、coarse aggregate gradation defined in Section 7.2.3. 7.2.3. Sieve all coarse aggregates to which this test method is applied and grade in accordance with the requirements in Table 3. Coarse aggregate fractions larger than 12.5-mm (12-in.) sieve are not to be tested as such. When petrographic examina
49、tion using ASTM C 295 reveals that the material making up the size fraction larger than the 12.5-mm (12-in.) sieve is of such a composition and lithology that no difference should be expected compared with the smaller size material, then no further attention need be paid to the larger sizes. If petrographic examination suggests the larger-size material to be more reactive, the material should be studied for its effect in concrete according to one or the other alternative procedures descr
