ACI 211 3R-2002 Guide for Selecting Proportions for No-Slump Concrete《干硬混凝土的比例选择指南[替代 ACI 211 3、ACI 211 3]》.pdf

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1、ACI 21 1.3R-02 (Reapproved 2009) Guide for Selecting Proportions for No-Slump Concrete Reported by ACI Committee 21 1 Michael J. Boyle Chair Terrence E. rnold* William L. Baninger Muhamme mixture proportioning; no-slump concrete; roller- compacted concrete; slump test; water-cementitious materials r

2、atio. 3.4-Selecting water-cementitious materials ratio 3.5-Estimate of coarse aggregate quantity ACI Committee Reports, Guides, Manuals, Standard Practices, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. This document is intended for the us

3、e of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. The American Concrete Institute disclaims any and all responsibility for the stated principles. The I

4、nstitute shall not be liable for any loss or damage arising therefrom. Reference to this document shall not be made in contract documents. If items found in this document are desired by the ArchitectiEngineer to be a part of the contract documents, they shall be restated in mandatory language for in

5、corporation by the ArchitectlEngineer. Chapter roof tiles (Appendix 4); concrete masonry units (CMU) (Appendix 5); and pervious concrete (Appendix 6). Vebe, s 32 to 18 18 to 10 10 to 5 5 to 3 3 to 0 - CHAPTER 2-PRELIMINARY CONSIDERATIONS 2.1-General The general comments contained in ACI 21 1.1 are p

6、ertinent to the procedures discussed in this guide. The description of the constituent materials of concrete, the differences in proportioning the ingredients, and the need for knowledge of the physical properties of the aggregate and cementitious materials apply equally to this guide. The level of

7、overdesign indicated in ACI 301 and ACI 3181318R should be applied to the compressive strength used for proportioning. - 2.2-Methods for measuring consistency Workability is the property of concrete that determines the ease with which it can be mixed, placed, consolidated, and finished. No- single t

8、est is available that will measure this property in quantitative terms. It is usually expedient to use some type of consistency measurement as an index to work- ability. Consistency may be defined as the relative ability of freshly mixed concrete to flow. The slump test is the most familiar test met

9、hod for consistency and is the basis for the measurement of consistency under ACI 2 1 1.1. No-slump concrete will have poor workability if consoli- dated by hand-rodding. If vibration is used, however, such concrete might be considered to have adequate workability. The range of workable mixtures can

10、 therefore be widened by consolidation techniques that impart greater energy into the mass to be consolidated. The Vebe the compacting factor apparatus,3 the modified compaction test, and the Thaulow drop table4 are laboratory devices that can provide a useful measure of consistency for concrete mix

11、tures with less than 25 mm (1 in.) slump. Of the three consistency measurements, the Vebe apparatus is frequently used today in roller-compacted concrete and will be referred to in this guide. The Vebe test is described in Appendix 2. If none of these methods are available, consolidation of the tria

12、l mixture under actual placing conditions in the field or laboratory will, of necessity, serve as a means for determining whether the consistency and workability are adequate. Suitable workability is often based on visual judgement for machine-made precast concrete products. A comparison of Vebe tes

13、t results with the conventional slump test is shown in Table 2.1. Note that the Vebe test can provide a measure of consistency in mixtures termed “extremely dry.“ Vebe time at compaction is influenced by other factors such as moisture condition of aggregates, time interval after mixing, and climatic

14、 conditions. Consistency description Extremely dry Very stiff Stiff Stiff plastic Plastic Very plastic 2.3-Mixing water requirement In ACI 2 1 1.1, approximate relative mixing water require- ments are given for concrete conforming to the consistency descriptions of stiff plastic, plastic, and very p

15、lastic, as shown in Table 2.2 of this guide. Considering the water requirement for the 75 to 100 mm (3 to 4 in.) slump as loo%, the relative water contents for those three consistencies are 92, 100, and 106%, respectively. haulod extended this concept of relative water contents to include stiffer mi

16、xtures, as shown in Table 2.2. Approximate relative water content, % haulo ow 78 83 88 93 100 106 Table 6.3.3, ACI 21 1.1 - - - 92 100 106 GUIDE FOR SELECTING PROPORTIONS FOR NO-SLUMP CONCRETE Maximum sue aggregate in. 419 399 379 r+itks. shW not be decreased ex as indi by labwakq tesb fir 359 -, E

17、0 339 g I m 319 g E 299 f $ 0 279 259 239 219 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 Maximum size aggregate mm Fig. 2.1-Approximate mixing water requirements for diferent consistencies and maximum-size aggregate for nonair-entrained concrete. M

18、aximum size aggregate mm Fig. 2.2-Approximate mixing water requirements for difSerent consistencies and maximum-size aggregate for air-entrained concrete. Figures 2.1 and 2.2 have been prepared based on the results from a series of laboratory tests in which the average air contents were as indicated

19、 in Fig. 2.3. These tests show that the factors in Table 2.2 need to be applied to the quantities given in ACI 21 1.1 to obtain the approximate water content for the six consistency designations. Approximate relative mixing water requirements are given in kg/m3 (1blyd3) using the relative water cont

20、ents shown by haulo ow for the stiff, very stiff, and extremely dry consistencies. For a given combination of materials, a number of factors will affect the actual mixing water requirement and can result in a considerable difference from the values shown in Fig. 2.1 and 2.2. These factors include pa

21、rticle shape and grading of the aggregate, air content and temperature of the concrete, the effectiveness of mixing, chemical admixtures, and the method of consolidation. With respect to mixing, for example, spiral-blade and pan-type mixers are more effec- tive for no-slump concretes than are rotati

22、ng-drum mixers. Maximum size of aggregate In. 318“ 112 518 314“ 1 .O“ 1 114“ 1 112“ 9 10 11 12 13 14 15 16 I7 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 Maximum size of aggregate mm Fw consistencies below 25mm (1 in.) slump, the volumes of air entrained by either an air-ent

23、raining cement or the usual amount of airentraining admixture used for more plastic rnixturw may be significantly lower then those shown. Fig. 2.3-Air content of concrete mixtures for different maximum size aggregate. CHAPTER 3-SELECTING PROPORTIONS 3.1-General Cementitious materials include the com

24、bined mass of cement, natd pozzolans, fly ash, ground granulated-blast-furnace slag (GGBFS), and silica fume that are used in the mixture. As recommended in ACI 2 1 1.1, concrete should be placed using the minimum quantity of mixing water consistent with mixing, placing, consolidating, and finishing

25、 requirements because this will have a favorable influence on strength, durability, and other physical properties. The major consid- erations in selecting proportions apply equally well to no-slump concretes as to the more plastic mixtures. These considerations are: Adequate durability in accordance

26、 with ACI 201.2R to satisfactorily withstand the weather and other destructive agents to which it may be exposed; Strength required to withstand the design loads with the required margin of safety; The largest maximum-size aggregate consistent with economic availability, satisfactory placement, and

27、concrete strength; The stiffest consistency that can be eficiently consoli- dated; and Member geometry. 3.2-Slump and maximum-size aggregate ACI 21 1.1 contains recommendations for consistencies in the range of stiff plastic to very plastic. These, as well as stiffer consistencies, are included in F

28、ig. 2.1 and 2.2. Consistencies in the very-stiff range and drier are often used in the fabrication of various precast elements such as, pipe, prestressed members, CMU, and roof tiles. Also, roller-compacted and pervious concretes fall into the no-slump categories as discussed in Appendix 3 through 6

29、. There is no apparent justification for setting limits for maximum and minimum consistency in the manufacture of these materials because the optimum consistency is highly dependent on the equipment, production methods, and materials used. It is further recommended that, wherever possible, the consi

30、stencies used should be in the range of very stiff or drier, because the use of these drier consistencies that are adequately consolidated will result in improved quality and a more economical product. The nominal maximum size of the aggregate to be selected for a particular type of construction is

31、dictated primarily by consid- eration of both the minimum dimension of a section and the minimum clear spacing between reinforcing bars, prestressing tendons, ducts for post-tensioning tendons, or other embedded items. The largest permissible maximum-size aggregate should be used; however, this does

32、 not preclude the use of smaller sizes if they are available and their use would result in equal or greater strength with no detriment to other concrete properties. For reinforced, precast concrete products such as pipe, the maximum coarse aggregate size is generally 19 mm (314 in.) or less. 3.3-Est

33、imating water and aggregate-grading requirements The quantity of water per unit volume of concrete required to produce a mixture of the desired consistency is influenced by the maximum size, particle shape, grading of the aggregate, and the amount of entrained air. It is relatively unaffected by the

34、 quantity of cementitious material below about 360 to 390 kg/m3 (610 to 660 lblyd3). In mixtures richer than these, mixing water requirements can increase significantly as cementitious materials contents are increased. Acceptable aggregate gradings are presented in ASTM C 33 and AASHTO M 6 and M 80.

35、 Aggregate grading is an important parameter in selecting proportions for concrete in machine-made precast products such as pipes, CMU, roof tile, manholes, and prestressed products. Forms for these products are removed immediately after the concrete is placed and consolidated, or the concrete GUlDE

36、 FOR SELECTING PROPOR1 rIONS FOR NO-SLUMP CONCRETE 211.3R-5 is placed by an extrusion process. In either case, the concrete has no external support immediately after placement and consolidation; therefore, the fresh .concrete mixture should be cohesive enough to retain its shape after consolidation.

37、 Cohesiveness is achieved by providing sufficient fines in the mixtures. Some of these fines can be obtained by careful selection of the fine aggregate gradings. Pozzolans, such as fly ash, have also been used to increase cohesiveness. In some cases, the desired cohesiveness can be improved by incre

38、asing the cementitious materials content. This approach is not recommended, however, because of negative effects of excessive cementitious materials such as greater heat of hydration and drying shrinkage. The quantities of water shown in Fig. 2.1 and 2.2 of this guide are sufficiently accurate for p

39、reliminary estimates of proportions. Actual water requirements need to be estab- lished in laboratory trials and verified by field tests. This should result in water-cementitious materials ratios (wlcm) in the range of 0.25 to 0.40 or higher. Examples of such adjustments are given further in this gu

40、ide. For machine-made, precast concrete products such as pipes and CMU, the general rule is to use as much water as the product will tolerate without slumping or cracking when the forms are stripped. 3.4-Selecting water-cementitious materials ratio The selection of wlcm depends on the required stren

41、gth. Figure 3.1 provides initial information for wlcm. The compressive strengths are for 150 x 300 mm (6 x 12 in.) cylinders, prepared in accordance with ASTM C 192, subjected to standard moist curing, and tested at 28 days in accordance with ASTM C 39 for the various ratios. The required wlcm to ac

42、hieve a desired strength depends on whether the concrete is air-entrained. Using the maximum permissible wlcm from Fig. 3.1 and the approximate mixing water requirement from Fig. 2.1 and 2.2, the cementitious material content can be calculated by dividing the mass of water needed for mixing by the w

43、lcm. If the specifications for the job contain a minimum cementitious material content requirement, the corresponding wlcm for estimating strength can be computed by dividing the mass of water by the mass of the cementitious material. The lowest of the three wlcm-those for durability, strength, or c

44、ementitious material content-should be selected for calculating concrete proportions. Air-entraining admixtures or air-entraining cements can be beneficial in ensuring durable concrete in addition to providing other advantages, such as reduction in the mixture harshness with no increase in water. Ai

45、r-entrained concrete should be used when the concrete products are expected to be exposed to frequent cycles of freezing and thawing in a moist, critically saturated condition. ASTM C 666 testing before construction is recommended to assess resistance to freezing- and-thawing characteristics.of the

46、no-slump concrete. If these no-slump concrete mixtures may be exposed to deicer salts, they should also be tested in accordance with ASTM C 666. Figure 3.1 is based on the air contents shown in Fig. 2.3. In Fig. 3.1 at equal wlcm, the strengths for the air-entrained 0 30 040 0.50 0.60 0.70 0.80 0.90

47、 water-cementitious materials ratio, by mass Values are estimated average strengths for concrete containing not more than the percentage of air shown in Fig. 2.3. For a constant water-cementitious materials ratlo. the strength of concrete is reduced as the air content is increased. Strength is based

48、 on 150 x 300 mm (6 x 12 in.) cylinders prepared in accordance with ASTM C 31131M and moist-cured 26 days at 23 r 1.7 C (73.4 * 3 OF). Reiatonsntp assumes maxlmum slze aggregale abot 19 to 25 mm (314 to 1 m ) for a alven some, strenarn proauced for a glven water-cementlo. marerta s ratlo WI I increa

49、se as maximum size of aggregatebecreases. Fig. 3. I-Relationships between water-cementitious materials ratio and compressive strength of concrete. concrete are approximately 20% lower than for the nonair-entrained concrete. These differences may not be as great in the no-slump mixtures because the volume of entrained air in these mixtures using an air-entraining cement, or the usual amount of air-entraining admixture per unit of cementitious material, will be reduced significantly with practically no loss in resistance to freezing and thawing and density. In addition, when cement