Baixe C87-Effect of Organic Impurities in Fine Aggregate on Strength e outras Notas de estudo em PDF para Química Industrial, somente na Docsity! Designation: C 87 – 83 (Reapproved 1995)e1 Standard Test Method for Effect of Organic Impurities in Fine Aggregate on Strength of Mortar1 This standard is issued under the fixed designation C 87; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. e1 NOTE—Section 13, Keywords, was added in November 1995. 1. Scope 1.1 This test method covers the determination of the effect on mortar strength of the organic impurities in fine aggregate, whose presence is indicated by tests with Test Method C 40. Comparison is made between compressive strengths of mortar made with washed and unwashed fine aggregate. 1.2 The SI values shown in parentheses are provided for information purposes only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety and health practices and determine the applica- bility of regulatory limitations prior to use. 2. Referenced Documents 2.1 ASTM Standards: C 33 Specification for Concrete Aggregates2 C 40 Test Method for Organic Impurities in Fine Aggre- gates for Concrete2 C 109/C 109M Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or 50-mm Cube Specimens)3 C 128 Test Method for Specific Gravity and Absorption of Fine Aggregate2 C 150 Specification for Portland Cement3 C 230 Specification for Flow Table for Use in Tests of Hydraulic Cement3 C 305 Practice for Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic Consistency3 C 670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials2 C 702 Practice for Reducing Samples of Aggregate to Testing Size2 D 75 Practice for Sampling Aggregates4 D 3665 Practice for Random Sampling of Construction Materials4 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 Specification C 33 concerning organic impurities. 3.2 This test method is only applicable to those samples which, when tested in accordance with Test Method C 40, have produced a supernatant liquid with a color darker than that of the reference standard color solution. 4. Basis for Comparison 4.1 The fine aggregate shall be compared in mortar, as described in this test method, with a sample of the same aggregate that has been washed in a 3 % solution of sodium hydroxide followed by thorough rinsing in water. The washing shall be repeated a sufficient number of times until the supernatant liquid obtained in Test Method C 40 has a color lighter than standard. (Note 1) The washing shall be performed in such a way as to minimize the loss of fines and so that the washed aggregate has a fineness modulus within 0.10 of that of the unwashed aggregate. The washed and rinsed aggregate shall be checked with a suitable indicator such as phenolphtha- lein or litmus to assure that sodium hydroxide has been removed effectively prior to preparation of the mortar. 4.2 Unless otherwise specified or permitted, strength com- parisons shall be made at 7 days in accordance with the following conditions: 4.2.1 Mix three batches of mortar with the aggregate washed in sodium hydroxide and three batches with the unwashed aggregate on the same day. Mix the batches for the two conditions alternately. 4.2.2 Mold three 2-in. or 50-mm cubes from each batch. 4.2.3 Test the three cubes from each batch at the age specified. NOTE 1—Test Method C 40 describes a standard procedure and an 1 This test method is under the jurisdiction of ASTM Committee C-9 on Concretes and Concrete Aggregatesand is the direct responsibility of Subcommittee C09.20on Normal Weight Aggregates. Current edition approved Oct. 28, 1983. Published December 1983. Originally published as C 87–31. Last Previous edition C 87–69 (1975). 2 Annual Book of ASTM Standards, Vol 04.02. 3 Annual Book of ASTM Standards, Vol 04.01. 4 Annual Book of ASTM Standards, Vol 04.03. 1 Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States. alternative procedure for the determination of color value. In the standard procedure there is a single reference standard color. In the alternative procedure five colored glass standards are used. The reference standard color is equivalent to color Plate No. 3. 5. Apparatus 5.1 Flow Table, Flow Mold, and Caliper, as described in Specification C 230. 5.2 Tamper, Trowel, Cube Molds, and Testing Machine, as described in Test Method C 109/C 109M. 5.3 Mixer, Bowl, and Paddle, as described in Practice C 305. 6. Reagents and Materials 6.1 Portland cement shall be Type I or Type II, meeting the requirements of Specification C 150. 6.2 Sodium Hydroxide Solution (3 %)—Dissolve 3 parts by weight of sodium hydroxide (NaOH) in 97 parts water. 7. Sampling 7.1 Sample portions of fine aggregate for this test shall be obtained from the same sample used for Test Method C 40. Needed reduction of samples to obtain test portions shall be in accordance with Practice C 702. 7.2 Secure an additional field sample if needed from the aggregate supply in accordance with Practice D 75 and Prac- tice D 3665. 8. Temperature 8.1 The temperature of the mixing water, moist closet, and storage tank shall be maintained at 73.4 63°F (23 61.7°C). 9. Preparation of Mortar 9.1 Prepare the mortar in a mechanical mixer in accordance with the procedure for mixing mortars described in Practice C 305, as modified below. 9.1.1 The mortar shall be proportioned to produce a consis- tency of 100 65 as determined by the flow test. 9.1.2 In the event that the fine aggregate being used includes particles so large that the adjustment bracket (as described in Practice C 305) cannot provide adequate clearance, the over- sized particles shall be removed by sieving on the 4.75-mm (No. 4) or 2.36-mm (No. 8) sieve. If this procedure is employed, the report shall so state and shall indicate the quantity of material so removed. NOTE 2—Caution: The clearances between the paddle and the bowl specified in Practice C 305 are suitable when using the standard mortar made with Ottawa Sand. To permit the mixer to operate freely and to 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 Practice C 305; a clearance of approximately 5.0 mm has been found to be satisfactory for this method when used with fine aggregate from which the material retained on the 4.75-mm sieve has been removed. 9.2 Use water and cement in quantities that will yield a water-cement ratio of 0.6 by mass. It has been found that 600 g of cement and 360 mL of water will usually be adequate for a 6-cube batch. 9.3 Using fine aggregate that has been brought to a saturated surface dry condition as described in Test Method C 128, prepare a quantity of aggregate estimated to provide slightly more than needed to produce a batch of the desired consis- tency. NOTE 3—If the absorption has been determined in accordance with Test Method C 128, the aggregate may be prepared for test 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 30 min before use. 9.4 After placing all the mixing water in the bowl, add the cement to the water. Start the mixer and mix at the slow speed (140 65 rpm) for 30 s. 9.5 While still mixing at slow speed over a 30-s period, add a measured quantity of aggregate estimated to provide the proper consistency. NOTE 4—The quantity of aggregate used may be determined by subtracting from a known quantity of prepared aggregate the mass of the portion remaining after mixing. 9.6 Stop the mixer, change to medium speed (285 610 rpm), and mix for 30 s. 9.7 Stop the mixer and let the mortar stand for 11⁄2 min. During the first 15 s of this interval, quickly scrape down into the batch any mortar that may have collected on the side of the bowl, then for the remainder of this interval, cover the bowl with the lid. 9.8 Finish by mixing for 1 min at medium speed. If the flow appears to be too high additional sand may be added after the first 30 s of this mixing period. If so, stop the mixer briefly, add the sand, and then complete the additional 30 s of mixing. 9.9 In any case requiring a remixing interval, any mortar adhering to the side of the bowl shall be quickly scraped down into the batch with the scraper prior to remixing. 9.10 Make a determination of the flow. 10. Procedure 10.1 Flow Test: 10.1.1 Carefully wipe the flow table top clean and dry and place the flow mold at the center. Immediately after completing the mixing operation, place a layer of mortar about 1 in. (25 mm) in thickness in the mold and tamp 20 times with the tamper. The tamping pressure shall be just sufficient to ensure uniform filling of the mold. Fill the mold with mortar and tamp as specified for the first layer. Cut off the mortar to a plane surface, flush with the top of the mold, by drawing the straight edge of the trowel (held nearly perpendicular to the mold) with a sawing motion across the top of the mold. Wipe the table top clean and dry, being especially careful to remove any water from around the edge of the flow mold. Lift the mold away from the mortar 1 min after completing the mixing operation. Immediately drop the table through a height of 1⁄2 in. (12.7 mm) ten times in 6 s. The flow is the resulting increase in average diameter of the mortar mass, measured on at least four diameters at approximately equal angles, expressed as a percentage of the original diameter. 10.1.2 Should the flow be too great, return the mortar to the mixing vessel, add additional sand, 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 100 65, C 87 2