1、Standard Method of Test for Effect of Organic Impurities in Fine Aggregate on Strength of Mortar AASHTO Designation: T 71-08 (2012)1ASTM Designation: C 87/C 87M-10 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-1c
2、 T 71-1 AASHTO Standard Method of Test for Effect of Organic Impurities in Fine Aggregate on Strength of Mortar AASHTO Designation: T 71-08 (2012)1ASTM Designation: C 87/C 87M-10 1. SCOPE 1.1. This test method covers the determination of the effect on mortar strength of the organic impurities in fin
3、e aggregate, whose presence is indicated by tests with T 21. Comparison is made between compressive strengths of mortar made with washed and unwashed fine aggregate. 1.2. The values stated in SI units are to be regarded as the standard. 1.3. This standard may involve hazardous materials, operations,
4、 and equipment. This standard does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
5、 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 6, Fine Aggregate for Hydraulic Cement Concrete M 85, Portland Cement M 152M/M 152, Flow Table for Use in Tests of Hydraulic Cement M 231, Weighing Devices Used in the Testing of Materials R 16, Regulatory Information for Chemicals Used in AASHTO Tes
6、ts T 2, Sampling of Aggregates T 21, Organic Impurities in Fine Aggregates for Concrete T 84, Specific Gravity and Absorption of Fine Aggregate T 106M/T 106, Compressive Strength of Hydraulic Cement Mortar (Using 50-mm or 2-in. Cube Specimens) T 162, Mechanical Mixing of Hydraulic Cement Pastes and
7、Mortars of Plastic Consistency T 248, Reducing Samples of Aggregate to Testing Size 2.2. ASTM Standard: C 670, Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials 2014 by the American Association of State Highway and Transportation Officials.All
8、rights reserved. Duplication is a violation of applicable law.TS-1c T 71-2 AASHTO 3. SIGNIFICANCE AND USE 3.1. This test method is of significance in making a final determination of the acceptability of fine aggregates with respect to the requirements of M 6 concerning organic impurities. 3.2. This
9、test method is only applicable to those samples which, when tested in accordance with T 21, have produced a supernatant liquid with a color darker than that of the reference standard color Plate No. 3 or color solution. 4. BASIS FOR COMPARISON 4.1. The fine aggregate that produced a color darker tha
10、n the standard in T 21 shall be compared in mortar, as described in this test method, with a sample of the same aggregate that has been washed in a solution of sodium hydroxide followed by thorough rinsing in water. The washing shall be repeated a sufficient number of times until the supernatant liq
11、uid obtained in T 21 has a color lighter than standard (Note 1). 4.2. Unless otherwise specified or permitted, strength comparisons shall be made at seven days in accordance with the following conditions: 4.2.1. Mix three batches of mortar with the aggregate washed in sodium hydroxide and three batc
12、hes with the unwashed aggregate on the same day. All batches shall have the same quantity of fine aggregate. Mix the batches for the two conditions alternately. 4.2.2. Mold three 50-mm or 2-in. cubes from each batch. 4.2.3. Test the three cubes from each batch at the age specified. Note 1T 21 descri
13、bes a standard procedure and an alternative procedure for the determination of color value. In the standard procedure, there is a single reference standard color. In the alternative procedure, five glass color standards are used. The reference standard color is equivalent to color Plate No. 3. 5. SA
14、MPLING AND SAMPLE PREPARATION 5.1. Sample portions of fine aggregate for this test shall be obtained from the same sample used for T 21. Needed reduction of samples to obtain test portions shall be in accordance with T 248. 5.2. Secure an additional field sample if needed from the aggregate supply i
15、n accordance with T 2. 5.3. In the event that the fine aggregate being used includes particles so large that the adjustment bracket (as described in T 162) cannot provide adequate clearance, the oversized particles shall be removed by sieving on the 4.75-mm (No. 4) or 2.36-mm (No. 8) sieve. If this
16、procedure is employed, the report shall so state and shall indicate the percentage of material so removed. Note 2Caution: The clearances between the paddle and the bowl specified in T 162 are suitable when using the standard mortar made with graded sand. To permit the mixer to operate freely and to
17、avoid serious damage to the paddle and bowl when coarser aggregates are used, it may be necessary to set the clearance adjustment bracket to provide greater clearances than specified. A clearance of approximately 4.0 mm is required in T 162; a clearance of approximately 5.0 mm has been found to be s
18、atisfactory for this method when used with fine aggregate from which the material retained on the 4.75-mm (No. 4) sieve has been removed. 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 71-3 AASH
19、TO 5.4. Split the fine aggregate to be used for these tests into two approximately equal portions, using Test Method T 248. Set one portion aside to be used in the unwashed condition. The second portion is to be washed before use. 5.5. Preparing Washed Fine Aggregate: 5.5.1. Perform the washing and
20、the rinsing of the fine aggregate with care to minimize the loss of fines, so that the aggregate after washing and rinsing has a fineness modulus within 0.10 of that of the unwashed aggregate. 5.5.2. Establishing a Standard for Thoroughness of RinsingPlace a small amount of the water to be used for
21、washing and rinsing in a clean, clear container, and determine the pH of the water by use of pH paper, pH meter, or add a drop of phenolphthalein to the wash water and retain for later comparison. 5.5.3. Washing the AggregatePlace sufficient quantity of fine aggregate for three batches in a suitable
22、 container, flood with the sodium hydroxide solution, and agitate thoroughly with a spoon or trowel. At the end of the washing and after allowing the fines to settle, siphon off as much of the sodium hydroxide as possible, without removing any of the aggregate fines. Aggregates containing particles
23、that float may be elutriated onto a No. 200 sieve to capture any floating particles. 5.5.4. Rinsing the AggregateAdd a large quantity of water to the washed aggregate, agitate, allow to stand for fines to settle, and then siphon off the rinse water. Repeat this operation several times, until the wat
24、er used for rinsing has a pH equal to or lower than the pH of the water prior to contact with the fine aggregate. If phenolphthalein was used as an indicator, the color of the wash water is equal to or lighter in color than the solution prepared in Section 5.5.2. 5.5.5. Verifying Removal of Organic
25、ImpuritiesRepeat the Test Method T 21 procedure to determine if the washing has removed sufficient organic impurities to produce a satisfactory result (color lighter than the standard). If the fine aggregate continues to produce an unsatisfactory result (color darker than the standard), repeat the w
26、ashing and rinsing procedure (described in Sections 5.5.3 and 5.5.4) as many times as necessary until a satisfactory result is obtained by Test Method T 21. 6. REAGENTS AND MATERIALS 6.1. Portland cement shall be Type I or Type II, meeting the requirements of M 85. 6.2. Sodium Hydroxide Solution (3
27、percent)Dissolve three parts by mass of sodium hydroxide (NaOH) in 97 parts water. 6.3. PhenolphthaleinDissolve 1 g of reagent grade phenolphthalein in 1 L of 95 percent reagent grade ethyl alcohol. 7. APPARATUS 7.1. Flow Table, Flow Mold, and Caliper, as described in M 152M/M 152. 7.2. Tamper, Trow
28、el, Cube Molds, and Testing Machine, as described in T 106M/T 106. 7.3. Mixer, Bowl, and Paddle, as described in T 162. 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 71-4 AASHTO 7.4. Balance, c
29、onforming to M 231 for Class G 5. 7.5. pH Paper, 014. 7.6. pH Meter, capable of reading 0.1 pH units or better. 8. TEMPERATURE 8.1. The temperature of the mixing water, moist closet, and storage tank shall be maintained at 23.0 1.7C (73.4 3F). 9. PREPARATION OF MORTAR 9.1. Number of Test BatchesPrep
30、are three batches of mortar using the washed aggregates and three batches of mortar using the unwashed aggregate, on the same day. Mix the batches, alternating between the washed and the unwashed aggregate. 9.2. Use water and cement in quantities that will yield a watercement ratio of 0.6 by mass. I
31、t has been found that 600 g of cement and 360 mL of water will usually be adequate for a six-cube batch. Note 3Use of cement, water, and an appropriate amount of aggregate for a six-cube batch, or larger, is recommended to assure uniform mixing of the mortar. 9.3. Using fine aggregate that has been
32、brought to a saturated surface-dry condition as described in T 84, prepare a quantity of aggregate estimated to provide slightly more than needed to produce a batch of the desired consistency. Note 4If the absorption has been determined in accordance with T 84, the aggregate may be prepared for test
33、 by adding to a known mass of dry aggregate the amount of water it will absorb, mixing thoroughly, and permitting the aggregate to stand in a covered pan for 60 min before use. The washed and unwashed aggregate may be presumed to have the same absorption. Note 5The mass of the prepared aggregate sho
34、uld be determined so that the amount actually used in a batch may be calculated as described in Section 10.1.3. Experience indicates that the quantity of fine aggregate used in a six-cube batch will range from approximately 1200 g for fine-graded material to approximately 2200 g for coarse-graded ma
35、terial. 9.3.1. The mortar shall be proportioned to produce a consistency of 110 5 in 25 drops of the flow table, as determined by the flow test described in T 106M/T 106. 9.4. Prepare the mortar in a mechanical mixer in accordance with the procedure for mixing mortars described in T 162, as modified
36、 below. Note 6Unwashed aggregate should be used in the initial batch, so that washed aggregate is not wasted in case the batch must be discarded. 9.4.1. During the period from 30 to 60 s from the start of mixing, and while still mixing at slow speed, slowly add a measured quantity of aggregate estim
37、ated to provide the proper consistency. 9.4.2. During the final 1 min of mixing at medium speed, if the flow appears to be too high, additional aggregate may be added after the first 30 s of this mixing period. To do so, stop the mixer briefly, add the aggregate, and then complete the additional 30
38、s of mixing. 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 71-5 AASHTO 10. PROCEDURE 10.1. Make a determination of the flow as described in T 106M/T 106. 10.1.1. Should the flow be too great, r
39、eturn the mortar to the mixing bowl, add additional aggregate, mix for 30 s at medium speed, and make another determination of the flow. If more than two trials must be made to obtain a flow of 110 5, consider the mortar as a trial mortar, and prepare test specimens from a new batch. 10.1.2. If the
40、mortar is too dry, discard the batch. 10.1.3. Determine the quantity of aggregate used by subtracting the mass of the portion remaining after mixing from the mass of the initial sample. Use this quantity of aggregate in all subsequent batches for the aggregate under test. 10.2. Molding Test Specimen
41、sImmediately following completion of a flow test indicating acceptable consistency, return the mortar from the flow table to the mixing bowl, scrape down the bowl, and then remix the entire batch 15 s at medium speed. Upon completion of mixing, shake the excess mortar from the paddle into the bowl.
42、Place the mortar in cube molds in two layers in accordance with the procedures described in T 106M/T 106. 10.3. For subsequent batches, use washed and unwashed aggregate alternately and the quantity of aggregate determined in Section 10.1.3. Follow the procedure for mixing mortars described in T 162
43、. Following the final 1-min mixing in T 162, do not perform a flow test but instead allow the mortar to stand in the mixing bowl 90 s without covering. During the last 15 s of this interval, quickly scrape down into the batch any mortar that may have collected on the side of the bowl. Then remix for
44、 15 s at medium speed. Upon completion of mixing, shake the excess mortar from the paddle into the mixing bowl. Place the mortar in the cube molds in two layers in accordance with the procedures described in T 106M/T 106. 10.4. Store the test specimens and determine compressive strength in accordanc
45、e with T 106M/T 106. 11. CALCULATION AND REPORT 11.1. Calculate the compressive strength of each specimen by dividing the maximum load it carried during the test by the cross-sectional area. Average the strengths of the three specimens from each batch. Calculate three strength ratios by dividing the
46、 average strength for a batch containing unwashed aggregate by the average strength for the corresponding (in respective order of mixing) batch containing washed aggregate. 11.2. Report the average of the three ratios, expressed as a percentage, as the relative strength for the aggregate under test.
47、 11.3. If the fine aggregate was sieved to remove particles coarser than the 4.75-mm (No. 4) sieve (as described in Section 5.3), so state in the report and indicate the quantity of material removed as a percentage of the original sample mass. 2014 by the American Association of State Highway and Tr
48、ansportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 71-6 AASHTO 12. PRECISION AND BIAS 12.1. The following precision statement is applicable when a test result is the average ratio, as defined by this test method, of three pairs of mortar batch strength t
49、ests with all the batches mixed on the same day and tested at the same age. 12.2. The single laboratory coefficient of variation has been determined to be 5.4 percent (Note 7). Therefore, results of two properly conducted tests in the same laboratory should not differ from each other by more than 15.3 percent (Note 7) of their average. The maximum range (difference between highest and lowest) of the three individual ratios used in calculating the average should not exceed 17 percent (Note 8). Note 7These numbers represent, respective
