1、Standard Method of Test for Visual Stability Index (VSI) of Self-Consolidating Concrete (SCC) AASHTO Designation: T 351-141American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3b T 351-1 AASHTO Standard Method of Test f
2、or Visual Stability Index (VSI) of Self-Consolidating Concrete (SCC) AASHTO Designation: T 351-1411. SCOPE 1.1. This test method covers determination of the visual stability index of self-consolidating concrete (SCC), both in the laboratory and in the field. SCC is defined as a highly workable concr
3、ete that can flow through densely reinforced or complex structural elements under its own weight without vibration and adequately fill voids without experiencing segregation or excessive bleeding. 1.2. The values stated in either SI units or inch-pound units are to be regarded separately as standard
4、. Within the text, the inch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard. 1.3. This standard does no
5、t purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: R
6、 60, Sampling Freshly Mixed Concrete T 119M/T 119, Slump of Hydraulic Cement Concrete T 347, Slump Flow of Self-Consolidating Concrete (SCC) 3. SUMMARY OF TEST METHOD 3.1. The Visual Stability Index (VSI) is a visual rating of the resistance to segregation of an SCC mixture and may be determined whe
7、n performing the Slump Flow Method of Test in T 347. A sample of freshly mixed self-consolidating concrete is placed in a mold shaped as the inverted frustum of a cone. The mold is raised, allowing the SCC to spread radially. The stability of the mixture is then rated visually and assigned a Visual
8、Stability Index based on the criteria in this document. 4. SIGNIFICANCE AND USE 4.1. This test method is applicable to SCC, defined in Section 1.1. 4.2. This test method is intended to provide the user with a procedure to assess the stability of SCC. The stability (or segregation resistance) of an S
9、CC mixture is the ability of the mixture to remain homogeneous in composition during transport, during placement, and subsequent to placement. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 351-
10、2 AASHTO The VSI does not quantify a property of the concrete mixture but is useful for quality control/consistency testing. 4.3. This test method is applicable to SCC having coarse aggregate up to 25 mm 1 in. 5. APPARATUS 5.1. MoldThe SCC shall be placed in an inverted slump cone mold conforming to
11、 the applicable requirements of T 119M/T 119. 5.2. Base PlateThe base plate shall be made of a stiff nonabsorbing material, at least 820 mm 32 in. square, marked with a circle indicating the central location for the slump cone, and a concentric circle with a diameter of 500 mm 20 in. 5.3. ScoopA sco
12、op of a size large enough so each amount of concrete obtained from the sampling receptacle is representative and small enough so it is not spilled during placement in the mold. 5.4. Strike-Off BarA flat straight bar of steel or other suitable metal at least 3 mm 1/8in. thick and 20 mm 3/4in. wide by
13、 300 mm 12 in. long. 5.5. Tape measure containing increments of 5 mm 0.25 in. or less. 6. SAMPLE 6.1. Approximately 6 L 0.2 ft3 of SCC is needed to perform the slump flow and VSI tests, sampled normally. 6.2. The sample of concrete shall be obtained in accordance with R 60. 7. PROCEDURE 7.1. Moisten
14、 the base plate and inside of the slump cone. 7.2. Place the base plate on a level stable surface and the inverted slump cone centrally on the base plate and hold down firmly (Figure 1). Figure 1Mold and Base Plate for Slump Flow Test (Inverted Cone Orientation) Minimum 820 mm 32 in.Base PlateInvert
15、ed Slump Cone 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 351-3 AASHTO 7.3. From the sample of concrete obtained in accordance with Section 6, fill the entire mold continuously. The mold shal
16、l be held firmly in place during filling. 7.4. Do not rod or tamp the SCC. Do not tap the sides of the cone or vibrate. 7.5. Use the strike-off bar to strike off the SCC level with the top of the cone. 7.6. Remove any spilled or struck-off SCC from around the base of the cone to preclude interferenc
17、e with movement of the flowing SCC. 7.7. Immediately raise the cone vertically 230 75 mm 9 3 in. above the base plate with no lateral or torsional motion within a time period of 3 1 s, and allow the SCC to flow out freely from within. Complete the steps described in Sections 7.3 through 7.7 within 2
18、1/2min. 7.8. If the Slump Flow Test of T 347 is being performed, diameters of the patty may be measured at this point. 7.9. Using the guidelines in Section 8, rate the stability of the mixture in 1.0 increments by visual examination of the SCC on the base plate and in the wheelbarrow or mixer. 8. IN
19、TERPRETATION OF RESULTS 8.1. In the case of severe segregation, most of the coarse aggregate may remain in the center of the slump flow patty of SCC. A border of mortar without coarse aggregate or a bleed water “halo” may occur at the edge of the slump flow patty of SCC. 8.2. Refer to Table 1 and Fi
20、gures 2 through 8 for assignment of Visual Stability Index. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 351-4 AASHTO Table 1Criteria for Visual Stability Index (VSI) of SCC Rating Criteria 0
21、No evidence of segregation in slump flow patty or in mixer drum or wheelbarrow. 1 No border of mortar without coarse aggregate in the slump flow patty, but some slight bleed or air popping on the surface of the concrete in the mixer drum or wheelbarrow. 2 A slight border of mortar without coarse agg
22、regate (10 mm 3/8in.) and/or large aggregate pile in the center of the slump flow patty and a thick layer of paste on the surface of the resting concrete in the mixer drum or wheelbarrow. Figure 2Visual Stability Index = 0 Figure 3Visual Stability Index = 1 2015 by the American Association of State
23、Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 351-5 AASHTO Figure 4Visual Stability Index = 1 Figure 5Visual Stability Index = 2 Figure 6Visual Stability Index = 2 2015 by the American Association of State Highway and Transportation Of
24、ficials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 351-6 AASHTO Figure 7Visual Stability Index = 3 Figure 8Visual Stability Index = 3 9. REPORT 9.1. Record the Visual Stability Index of the mixture. 10. PRECISION AND BIAS 10.1. No precision and bias statements are avai
25、lable at this time. 11. KEYWORDS 11.1. Halo; SCC; segregation; self-consolidating concrete; slump flow; stability; Visual Stability Index; VSI; workability. 1Formerly AASHTO Provisional Standard TP 80. First published as a full standard in 2014. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
