Self-Consolidating Concrete for Cast-in-Place Bridge Components (2016)

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A-1 Proposed Changes to the AASHTO LRFD Bridge Design and Construction Specifications These proposed changes to the Seventh Edition (2014) of the AASHTO LRFD Bridge Design Specifications and Third Edition (2010) of the AASHTO LRFD Bridge Construction Specifica- tions with 2014 Interim Revisions are the recommendations of the NCHRP Project 18-16 staff at the University of Nebraska-Lincoln. These specifications have not been approved by NCHRP or any AASHTO committee nor formally accepted for the AASHTO specifications. A t t A c h m e n t A

A-2 A.1 Bridge Design Specifications 5.4—MATERIAL PROPERTIES 5.4.2—Normal Weight and Structural Lightweight Concrete 5.4.2.1—Compressive Strength For each component, the specified compressive strength, f’ c, or the class of concrete shall be shown in the contract documents. Design concrete strengths above 10.0 ksi for normal weight concrete shall be used only when allowed by specific Articles or when physical tests are made to establish the relationships between the concrete strength and other properties. Specified concrete with strengths below 2.4 ksi should not be used in structural applications. The specified compressive strength for prestressed concrete and decks shall not be less than 4.0 ksi. For lightweight structural concrete, air dry unit weight, strength, and any other properties required for the application shall be specified in the contract documents. C5.4.2.1 The evaluation of the strength of the concrete used in the work should be based on test cylinders produced, tested, and evaluated in accordance with Section 8 of the AASHTO LRFD Bridge Construction Specifications. This Section was originally developed based on an upper limit of 10.0 ksi for the design concrete compressive strength. As research information for concrete compressive strengths greater than 10.0 ksi becomes available, individual Articles are being revised or extended to allow their use with higher strength concretes. Appendix C5 contains a listing of the Articles affected by concrete compressive strength and their current upper limit. It is common practice that the specified strength be attained 28 days after placement. Other maturity ages may be assumed for design and specified for components that will receive loads at times appreciably different than 28 days after placement. It is recommended that the classes of concrete shown in Table C5.4.2.1-1 and their corresponding specified strengths be used whenever appropriate. The classes of concrete indicated in Table C5.4.2.1-1 have been developed for general use and are included in AASHTO LRFD Bridge Construction Specifications, Section 8 “Concrete Structures” from which Table C5.4.2.1-1 was taken. These classes are intended for use as follows: Class A concrete is generally used for all elements of structures, except when another class is more appropriate, and specifically for concrete exposed to saltwater. Class B concrete is used in footings, pedestals, massive pier shafts, and gravity walls. Class C concrete is used in thin sections, such as reinforced railings less than 4.0 in. thick, for filler in steel grid floors, etc. Class P concrete is used when strengths in excess of 4.0 ksi are required. For prestressed concrete, consideration should be given to limiting the nominal aggregate size to 0.75 in. Class S concrete is used for concrete deposited underwater in cofferdams to seal out water. Class SCC is intended for all cast-in-place elements of structures when it is needed/required to eliminate mechanical consolidation. Strengths above 5.0 ksi should be used only when the availability of materials for such concrete in the locale is verified. Lightweight concrete is generally used only under conditions where weight is critical. In the evaluation of existing structures, it may be appropriate to modify the f’c and other attendant structural properties specified for the original construction to

A-3 For concrete Classes A, A(AE), and P used in or over saltwater, the W/C ratio shall be specified not to exceed 0.45. The sum of Portland cement and other cementitious materials shall be specified not to exceed 800 pcy, except for Class P (HPC) concrete where the sum of Portland cement and other cementitious materials shall be specified not to exceed 1000 pcy. Air-entrained concrete, designated “AE” in Table C5.4.2.1-1, shall be specified where the concrete will be subject to alternate freezing and thawing and exposure to deicing salts, saltwater, or other potentially damaging environments. recognize the strength gain or any strength loss due to age or deterioration after 28 days. Such modified f’c should be determined by core samples of sufficient number and size to represent the concrete in the work, tested in accordance with AASHTO T 24M/T 24 (ASTM C42). There is considerable evidence that the durability of reinforced concrete exposed to saltwater, deicing salts, or sulfates is appreciably improved if, as recommended by ACI 318, either or both the cover over the reinforcing steel is increased or the W/C ratio is limited to 0.40. If materials, with reasonable use of admixtures, will produce a workable concrete at W/C ratios lower than those listed in Table C5.4.2.1-1, the contract documents should alter the recommendations in Table C5.4.2.1-1 appropriately. The specified strengths shown in Table C5.4.2.1-1 are generally consistent with the W/C ratios shown. However, it is possible to satisfy one without the other. Both are specified because W/C ratio is a dominant factor contributing to both durability and strength; simply obtaining the strength needed to satisfy the design assumptions may not ensure adequate durability. Table C5.4.2.1-1 Concrete Mix Characteristics by Class Class of Concrete Minimum Cement Content Maximum W/C Ratio Air Content Range Coarse Aggregate Per AASHTO M43 (ASTM D448) 28-Day Compressive Strength pcy lbs Per lbs % Square Size of Opening (in.) ksi A A(AE) 611 611 0.49 0.45 - 6.0 ± 1.5 1.0 to No. 4 1.0 to No. 4 4.0 4.0 B 517 0.58 - 2.0 to No. 3 and No. 3 to No. 4 2.4 B(AE) 517 0.55 5.0 ± 1.5 2.0 to No. 3 and No. 3 to No. 4 2.4 C C(AE) 658 658 0.49 0.45 - 7.0 ± 1.5 0.5 to No. 4 0.5 to No. 4 4.0 4.0 P P(HPC) 564 0.49 As specified elsewhere 1.0 to No. 4 2.0 or 0.75 to No. 4 As specified elsewhere S 658 0.58 1.0 to No. 4 - Lightweight 564 As specified in the contract documents SCC SCC(AE) 658 658 0.44* 0.44* - 6.0 ± 1.5 0.75 to No. 4 0.75 to No. 4 4.0 4.0 *Water-to-powder ratio (W/P) is used when limestone powder is added as a filler in SCC mixtures up to 15%.

A-4 5.4.2.3—Shrinkage and Creep 5.4.2.3.1—General Values of shrinkage and creep, specified herein and in Articles 5.9.5.3 and 5.9.5.4, shall be used to determine the effects of shrinkage and creep on the loss of prestressing force in bridges other than segmentally constructed ones. These values in conjunction with the moment of inertia, as specified in Article 5.7.3.6.2, may be used to determine the effects of shrinkage and creep on deflections. These provisions shall be applicable for specified concrete strengths up to 15.0 ksi. In the absence of more accurate data, the shrinkage coefficients may be assumed to be 0.0002 after 28 days and 0.0005 after one year of drying. When mix-specific data are not available, estimates of shrinkage and creep may be made using the provisions of: Articles 5.4.2.3.2 and 5.4.2.3.3, The CEB-FIP model code, or ACI 209. For segmentally constructed bridges, a more precise estimate shall be made, including the effect of: Specific materials, Structural dimensions, Site conditions, and Construction methods, and Concrete age at various stages of erection. 5.4.2.3.2—Creep The creep coefficient may be taken as: (5.4.2.3.2-1) in which: where: H = relative humidity (%). In the absence of better information, H may be taken from Figure 5.4.2.3.3-1. ks = factor for the effect of the volume-to-surface ratio of the component. kf = factor for the effect of concrete strength. khc = humidity factor for creep. ktd = time development factor. t = maturity of concrete (day), defined as age of C5.4.2.3.1 Creep and shrinkage of concrete are variable properties that depend on a number of factors, some of which may not be known at the time of design. Without specific physical tests or prior experience with the materials, the use of the empirical methods referenced in these specifications cannot be expected to yield results with errors less than ±50 percent. C5.4.2.3.2 The methods of determining creep and shrinkage, as specified herein and in Article 5.4.2.3.3, are based on Huo et al. (2001), Al-Omaishi (2001), Tadros (2003), and Collins and Mitchell (1991). These methods are based on the recommendation of ACI Committee 209 as modified by additional recently published data. Other applicable references include Rusch et al. (1983), Bazant and Wittman (1982), and Ghali and Favre (1986). The creep coefficient is applied to the compressive strain caused by permanent loads in order to obtain the strain due to creep. Creep is influenced by the same factors as shrinkage, and also by: Magnitude and duration of the stress, Maturity of the concrete at the time of loading, and Temperature of concrete. Creep shortening of concrete under permanent loads is generally in the range of 0.5 to 4.0 times the initial elastic shortening, depending primarily on concrete maturity at the time of loading. Based on the work by Morcous, et al. (2015), the AASHTO method for determining creep coefficient yields reasonable predictions for normal weight SCC mixtures except those containing 15% limestone powder as a filler. In this case, creep coefficient is expected to be 20% higher than predicted using Eq.

A-5 concrete between time of loading for creep calculations, or end of curing for shrinkage calculations, and time being considered for analysis of creep or shrinkage effects. ti = age of concrete at time of load application (day). V/S = volume-to-surface ratio (in.). f ′ci = specified compressive strength of concrete at time of prestressing for pretensioned members and at time of initial loading for nonprestressed members. If concrete age at time of initial loading is unknown at design time, f ′ci may be taken as 0.80 f ′c (ksi). The surface area used in determining the volume- to-surface ratio should include only the area that is exposed to atmospheric drying. For poorly ventilated enclosed cells, only 50 percent of the interior perimeter should be used in calculating the surface area. For precast members with cast-in-place topping, the total precast surface should be used. For pretensioned stemmed members (I-beams, T-beams, and box beams), with an average web thickness of 6.0 to 8.0 in., the value of kvs may be taken as 1.00. 5.4.2.3.3—Shrinkage For concretes devoid of shrinkage-prone aggregates, the strain due to shrinkage, εsh, at time, t, may be taken as: (5.4.2.3.3-1) In which: khs = (2.00 – 0.014 H) (5.4.2.3.3-2) where: khs = humidity factor for shrinkage. kp = SCC powder composition factor to be determined by physical tests. In the absence of physical tests, kp shall be taken as 1.6 for cement type I/II with 25% Class C fly ash; 1.4 for cement type I/II with 30% GGBFS; and 1.3 for cement type I/II with 25% Class F fly ash or 20% Class F fly ash and 15% limestone powder. For conventionally vibrated concrete, kp shall be taken as 1.0. If the concrete is exposed to drying before 5 days of curing have elapsed, the shrinkage as determined in Eq. 5.4.2.3.3-1 should be increased by 20 percent. 5.4.2.3.2-1. The time development of shrinkage, given by Eq. 5.4.2.3.2-5, is proposed to be used for both precast concrete and cast-in-place concrete components of a bridge member, and for both accelerated curing and moist curing conditions. This simplification is based on a parametric study documented in Tadros (2003), on prestress losses in high strength concrete. It was found that various time development prediction methods have virtually no impact on the final creep and shrinkage coefficients, prestress losses, or member deflections. It was also observed in that study that use of modern concrete mixtures with relatively low water/cement ratios and with high range water reducing admixtures, has caused time development of both creep and shrinkage to have similar patterns. They have a relatively rapid initial development in the first several weeks after concrete placement and a slow further growth thereafter. For calculation of intermediate values of prestress losses and deflections in cast-in-place segmental bridges constructed with the balanced cantilever method, it may be warranted to use actual test results for creep and shrinkage time development using local conditions. Final losses and deflections would be substantially unaffected whether Eq. 5.4.2.3.2-5 or another time-development formula is used. C5.4.2.3.3 Shrinkage of concrete can vary over a wide range from nearly nil if continually immersed in water to in excess of 0.0008 for thin sections made with high shrinkage aggregates and sections that are not properly cured. Shrinkage is affected by: Aggregate characteristics and proportions, Average humidity at the bridge site, W/C ratio, Type of cure, Volume to surface area ratio of member, and Duration of drying period. Based on the work by Morcous, et al. (2015), the AASHTO method for determining shrinkage strains of concrete yields low predictions for normal weight SCC mixtures depending on the powder composition. Therefore, a powder composition factor is proposed with recommended values for the compositions being those used in this study. Large concrete members may undergo substantially less shrinkage than that measured by laboratory testing of small specimens of the same concrete. The constraining effects of reinforcement and composite

A-6 actions with other elements of the bridge tend to reduce the dimensional changes in some components. 5.4.2.4—Modulus of Elasticity In the absence of measured data, the modulus of elasticity, Ec, for concretes with unit weights between 0.090 and 0.155 kcf and specified compressive strengths up to 15.0 ksi may be taken as: (5.4.2.4-1) where: K1 = correction factor for source of aggregate to be taken as 1.0 unless determined by physical test, and as approved by the authority of jurisdiction. K2 = correction factor for concrete class to be taken as 0.96 for SCC and 1.0 for other classes of concrete unless determined by physical tests. wc = unit weight of concrete (kcf); refer to Table 3.5.1- 1 or Article C5.4.2.4. f ′c specified compressive strength of concrete (ksi). 5.4.2.6—Modulus of Rupture Unless determined by physical tests, the modulus of rupture, fr in ksi, for specified concrete strengths up to 15.0 ksi, may be taken as: For normal weight concrete: o Except as specified below ................. 0.24√f’c o When used to calculate the cracking moment of a member in Article 5.8.3.4.3 ................0.20√f’c For lightweight concrete: o For sand-lightweight concrete …....... 0.20√f’c o For all-lightweight concrete .............. 0.17√f’c When physical tests are used to determine modulus of rupture, the tests shall be performed in accordance with AASHTO T 97 and shall be performed on concrete using the same proportions and materials as specified for the structure. C5.4.2.4 See commentary for specified strength in Article 5.4.2.1. For normal weight concrete with wc = 0.145 kcf, Ec may be taken as: (C5.4.2.4-1) Test data show that the modulus of elasticity of concrete is influenced by the stiffness of the aggregate. The factor K1 is included to allow the calculated modulus to be adjusted for different types of aggregate and local materials. Unless a value has been determined by physical tests, K1 should be taken as 1.0. Use of a measured K1 factor permits a more accurate prediction of modulus of elasticity and other values that utilize it. The concrete class correction factor K2 is introduced based on the work by Morcous et al. (2015) to account for the effect of high paste-to-coarse aggregate volume in normal weight SCC mixtures. The research findings also indicate that the correction factor for source of aggregate K1 is 1.0 and 0.95 for the crushed limestone and natural gravel used in the study, respectively. C5.4.2.6 Most modulus of rupture test data on normal weight concrete are between 0.24√f’c and 0.37√f’c (ACI 1992; Walker and Bloem 1960; Khan, Cook, and Mitchell 1996). A value of 0.37√f’c has been recommended for the prediction of the tensile strength of high-strength concrete (ACI, 1992). However, the modulus of rupture is sensitive to curing method and nearly all of the test units in the dataset mentioned previously were moist cured until testing. Carrasquillio et al. (1981) noted a 26 percent reduction in the 28-day modulus of rupture if high-strength units were allowed to dry after 7 days of moist curing over units that were moist cured until testing. The flexure cracking stress of concrete members has been shown to significantly reduce with increasing member depth. Shioya et al. (1989) observed that the flexure cracking strength is proportional to H-0.25 where H is the overall depth of the flexural member in inches. Based on this observation, a 36.0 in. deep girder should achieve a flexural cracking stress that is 26 percent lower than that of a 6 in. deep modulus of rupture test. Since modulus of rupture units were either 4.0 or 6.0 in. deep and moist cured up to the time of testing, the modulus of rupture should be significantly greater than that of an average size bridge member composed of the same concrete. Therefore, 0.24√f’c is appropriate for checking minimum reinforcement in Article 5.7.3.3.2. =

A-7 5.4.2.7—Tensile Strength Direct tensile strength may be determined by either using ASTM C900, or the split tensile strength method in accordance with AASHTO T 198 (ASTM C496). The properties of higher strength concretes are particularly sensitive to the constitutive materials. If test results are to be used in design, it is imperative that tests be made using concrete with not only the same mix proportions, but also the same materials as the concrete used in the structure. The given values may be un-conservative for tensile cracking caused by restrained shrinkage, anchor zone splitting, and other such tensile forces caused by effects other than flexure. The direct tensile strength stress should be used for these cases. Based on the work by Morcous et al. (2015), the modulus of rupture test data of normal weight SCC are between 0.24√f’c and 0.37√f’c, similar to other classes of concrete. C5.4.2.7 For normal weight concrete with specified compressive strengths up to 10 ksi, the direct tensile strength may be estimated as fr = 0.23√f’c. Based on the work by Morcous et al. (2015), the splitting tensile strength of normal weight SCC may be estimated as fr = 0.18√f’c. 5.8—SHEAR AND TORSION 5.8.3—Sectional Design Model 5.8.3.3—Nominal Shear Resistance The nominal shear resistance, Vn, shall be determined as the lesser of: Where transverse reinforcement consists of a single longitudinal bar or a single group of parallel longitudinal bars bent up at the same distance from the support, the shear resistance Vs provided by these bars shall be determined as: where: C5.8.3.3 The shear resistance of a concrete member may be separated into a component, Vc, that relies on tensile stresses in the concrete, a component, Vs, that relies on tensile stresses in the transverse reinforcement, and a component, Vp, that is the vertical component of the prestressing force. The expressions for Vc and Vs apply to both prestressed and nonprestressed sections, with the terms β and θ depending on the applied loading and the properties of the section. Based on the work by Morcous, et al. (2015), the AASHTO method for determining the shear resistance component Vc of normal weight concrete members yields reasonable predictions for normal weight SCC members. The upper limit of Vn, given by Eq. 5.8.3.3-2, is intended to ensure that the concrete in the web of the beam will not crush prior to yield of the transverse reinforcement. As noted in Article 5.8.2.4 for members subjected to flexural shear without torsion, transverse reinforcement with specified minimum yield strengths

A-8 bv = effective web width taken as the minimum web width within the depth dv as determined in Article 5.8.2.9 (in.). dv = effective shear depth as determined in Article 5.8.2.9 (in.). s = spacing of transverse reinforcement measured in a direction parallel to the longitudinal reinforcement (in.). β = factor indicating ability of diagonally cracked concrete to transmit tension and shear as specified in Article 5.8.3.4. θ = angle of inclination of diagonal compressive stresses as determined in Article 5.8.3.4 (degrees); if the procedures of Article 5.8.3.4.3 are used, cot θ is defined therein . α = angle of inclination of transverse reinforcement to longitudinal axis (degrees). Av = area of shear reinforcement within a distance s (in.2). Vp = component in the direction of the applied shear of the effective prestressing force; positive if resisting the applied shear; Vp = 0 when Article 5.8.3.4.3 is applied (kip). Where bent longitudinal reinforcement is used, only the center three-fourths of the inclined portion of the bent bar shall be considered effective for transverse reinforcement. Where more than one type of transverse reinforcement is used to provide shear resistance in the same portion of a member, the shear resistance Vs shall be determined as the sum of Vs values computed from each type. Where shear resistance is provided by bent longitudinal reinforcement or a combination of bent longitudinal reinforcement and stirrups, the nominal shear resistance shall be determined using the simplified procedure in accordance with Article 5.8.3.4.1. 5.8.4—Interface Shear Transfer—Shear Friction 5.8.4.3—Cohesion and Friction Factors The following values shall be taken for cohesion, c, and friction factor, µ : For a cast-in-place concrete slab on clean concrete girder surfaces, free of laitance with surface roughened to an amplitude of 0.25 in.: c = 0.28 ksi µ = 1.0 K1 = 0.3 K2 = 1.8 ksi for normal weight concrete = 1.3 ksi for lightweight concrete For normal weight concrete placed monolithically: c = 0.40 ksi up to 100 ksi is permitted for elements and connections specified in Article 5.4.3.3. The angle θ is, therefore, also taken as the angle between a strut and the longitudinal axis of a member. Vp is part of Vcw by the method in Article 5.8.3.4.3 and thus Vp needs be taken as zero in Eq. 5.8.3.3-1. Requirements for bent bars were added to make the provisions consistent with those in AASHTO (2002). C5.8.4.3 The values presented provide a lower bound of the substantial body of experimental data available in the literature (Loov and Patnaik, 1994; Patnaik, 1999; Mattock, 2001; Slapkus and Kahn, 2004). Furthermore, the inherent redundancy of girder/slab bridges distinguishes this system from other structural interfaces. The values presented apply strictly to monolithic concrete. These values are not applicable for situations where a crack may be anticipated to occur at a Service

A-9 µ = 1.4 K1 = 0.25 K2 = 1.5 ksi For lightweight concrete placed monolithically, or nonmonolithically, against a clean concrete surface, free of laitance with surface intentionally roughened to an amplitude of 0.25 in.: c = 0.24 ksi µ = 1.0 K1 = 0.25 K2 = 1.0 ksi For normal weight concrete placed against a clean concrete surface, free of laitance, with surface intentionally roughened to an amplitude of 0.25 in.: c = 0.24 ksi µ = 1.0 K1 = 0.25 K2 = 1.5 ksi For concrete anchored to as-rolled structural steel by headed studs or by reinforcing bars where all steel in contact with concrete is clean and free of paint: c = 0.025 ksi µ = 0.7 K1 = 0.2 K2 = 0.8 ksi For brackets, corbels, and ledges, the cohesion factor, c, shall be taken as 0.0. For normal weight SCC with specified compressive strength less than 6 ksi placed monolithically, the cohesion factor, c, shall be taken as 0.0 unless determined by physical tests. Limit State. The factors presented provide a lower bound of the experimental data available in the literature (Hofbeck, Ibrahim, and Mattock, 1969; Mattock, Li, and Wang, 1976; Mitchell and Kahn, 2001). Available experimental data demonstrates that only one modification factor is necessary, when coupled with the resistance factors of Article 5.5.4.2, to accommodate both all-lightweight and sand- lightweight concrete. Note this deviates from earlier specifications that distinguished between all- lightweight and sand-lightweight concrete. Due to the absence of existing data, the prescribed cohesion and friction factors for nonmonolithic lightweight concrete are accepted as conservative for application to monolithic lightweight concrete. Tighter constraints have been adopted for roughened interfaces, other than cast-in-place slabs on roughened girders, even though available test data do not indicate more severe restrictions are necessary. This is to account for variability in the geometry, loading, and lack of redundancy at other interfaces. Since the effectiveness of cohesion and aggregate interlock along a vertical crack interface is unreliable, the cohesion component in Eq. 5.8.4.1-3 is set to 0.0 for brackets, corbels, and ledges. Based on the work by Morcous et al. (2015), the AASHTO method for determining interface shear resistance of normal weight concrete placed monolithically overestimates the interface shear resistance of normal weight SCC with compressive strength less than 6 ksi. Therefore, the cohesion factor, c, shall be taken as 0.0 in this case. 5.11—DEVELOPMENT AND SPLICES OF REINFORCEMENT 5.11.2—Development of Reinforcement 5.11.2.1—Deformed Bars and Deformed Wire in Tension The provisions herein may be used for No. 11 bars and smaller in normal weight concrete with specified concrete compressive strengths between 10.0 and 15.0 ksi for design (f’c). Transverse reinforcement consisting of at least No. 3 bars at 12 in. center shall be provided along the required development length where the C5.11.2.1 The extension of this article to concrete strengths between 10.0 and 15.0 ksi is limited to No. 11 bars and smaller based on the work presented in NCHRP Report 602 (Ramirez and Russel, 2008). The requirement of minimum transverse reinforcement along the development length is based on research by

A-10 specified concrete compressive strength is greater than 10 ksi. For straight bars having a specified minimum yield strength greater than 75 ksi, transverse reinforcement satisfying the requirements of Article 5.8.2.5 for beams and Article 5.10.6.4 for columns shall be provided over the required development length. 5.11.2.1.1—Tension Development Length The tension development length, d, shall not be less than the product of the basic tension development length, db, specified herein and the modification factor or factors specified in Articles 5.11.2.1.2 and 11.2.1.3. The tension development length shall not be less than 12.0 in., except for lap splices specified in Article 5.11.5.3.1 and development of shear reinforcement specified in Article 5.11.2.6. The basic tension development length, db, in in. shall be taken as: where: Ab = area of bar or wire (in.2). fy = specified yield strength of reinforcing bars (ksi). f ′c = specified compressive strength of concrete at 28 days, unless another age is specified (ksi). db = diameter of bar or wire (in.). 5.11.2.1.2—Modification Factors which Increase d The basic development length, db, shall be multiplied by the following factor or factors, as applicable: For top horizontal or nearly horizontal reinforcement, so placed that more than 12.0 in. of fresh concrete is cast below the reinforcement .................................................... 1.4 For lightweight aggregate concrete where fct (ksi) is specified .................................... For all-lightweight concrete where fct is not specified ............................................................ 1.3 For sand-lightweight concrete where fct is not specified ............................................................ 1.2 Linear interpolation may be used between all- Azizinamini et al. (1999). Transverse reinforcement used to satisfy the shear requirements may simultaneously satisfy this provision. Confining requirement is not required in bridge slabs or decks. Based on the work by Morcous et al. (2015), pull- out test data of No. 6 horizontal bars placed in normal weight SCC walls shows similar bond strength to that of bars placed in conventionally vibrated concrete walls. Also, top-bar effect on bond strength of high- slump flow SCC is lower than that of low-slump flow SCC and conventionally vibrated concrete. 0.1 22.0 ' ≥ ct c f f

A-11 lightweight and sand-lightweight provisions when partial sand replacement is used. For vertical or nearly vertical reinforcement placed in fresh SCC ………………………………… 1.3 For epoxy-coated bars with cover less than 3db or with clear spacing between bars less than 6db ..................................................................... 1.5 For epoxy-coated bars not covered above ........ 1.2 The product obtained when combining the factor for top reinforcement with the applicable factor for epoxy-coated bars need not be taken to be greater than 1.7. Based on the work by Morcous et al. (2015), pull- out test data of No. 6 vertical bars placed in SCC blocks shows lower bond strength than that of bars placed in conventionally vibrated concrete blocks. Therefore, a modification factor of 1.3 is proposed unless determined by physical tests.

A-12 A.2 Bridge Construction Specifications Section 3: Temporary Works 3.2 – FALSEWORK AND FORMS 3.2.3 – Formwork Design and Construction 3.2.3.2 – Design The structural design of formwork shall conform to the ACI Standard, Recommended Practice for Concrete Formwork (ACI 347), or some other generally accepted and permitted standard. In selecting the hydrostatic pressure to be used in the design of forms, consideration shall be given to the maximum rate of concrete placement to be used, the effects of vibration, the temperature of the concrete, and any expected use of set-retarding admixtures or pozzolanic materials in the concrete mix. When SCC is used, full hydrostatic pressure should be considered in designing the forms unless a mockup form is built and actual formwork pressure is measured in accordance to AASHTO T 352 using the same mixture, placement rate, and temperature. Section 8: Concrete Structures 8.2 – CLASSES OF CONCRETE 8.2.2 – Normal Weight (-Density) Concrete Twelve classes of normal weight (-density) concrete are provided for in these specifications as listed in Table 8.2.2-1, except that for concrete on or over saltwater or exposed to deicing chemicals, the maximum water/cement ratio shall be 0.45. Coarse aggregate for Class B and Class B(AE) shall be furnished into separate sizes as shown in Table 8.2.2-1. C3.2.3.2 Formwork design refers to ACI 347-78, Recommended Practice for Concrete Formwork. Based on the work by Morcous et al. (2015), the formwork pressure of SCC could be less than full hydrostatic pressure depending on the placement rate, temperature, and rheological properties of SCC. C8.2.2 With high performance concrete, it is desirable that the specifications be performance-based. Class P(HPC) is intended for use in prestressed concrete members with a specified concrete compressive strength greater than 6.0 ksi and should always be used for specified concrete strengths greater than 10.0 ksi. Class A(HPC) is intended for use in cast-in-place construction where performance criteria in addition to concrete compressive strengths are specified. Other criteria might include shrinkage, chloride permeability, freeze- thaw resistance, deicer scaling resistance, abrasion resistance, or heat of hydration. For both classes of concrete, a minimum cement content is not included since this should be selected by the producer based on the specified performance criteria. Maximum water-cementitious materials ratios have been included. The value of 0.40 for Class P(HPC) is less than the value of 0.49 for Class P, whereas the value of 0.45 for Class A(HPC) is the same as that for Class A(AE). For Class P(HPC) concrete, a maximum size of coarse aggregate is specified since it is difficult to achieve the higher concrete compressive strengths with aggregates larger than 0.75 in. For Class A(HPC) concrete, the maximum aggregate size should be selected by the producer based on the specified performance criteria. Air content for Class A(HPC) and P(HPC) should be

A-13 set with trial tests but a minimum of two percent is recommended. The 28-day specified compression strength may not be appropriate for strengths greater than 6.0 ksi. Classes SCC and SCC(AE) are intended for all cast-in-place elements of structures where mechanical consolidation is required to be eliminated or is impractical. In addition to strength, other performance criteria, such as filling ability, passing ability, and stability need to be specified. Table 8.2.2-1 Classification of Normal Weight Concrete Class of Concrete Minimum Cement Content Maximum Water/Cementitious Material Ratio Air Content Range Size of Coarse Aggregate Per AASHTO M43 (ASTM D448) Size Numbera Specified Compressive Strength lb/yd3 lb per lb % Square Size of Opening (in.) ksi at days A 611 0.49 - 1.0 to No. 4 57 4.0 at 28 A(AE) 611 0.45 6.0 ± 1.5 1.0 to No. 4 57 4.0 at 28 B 517 0.58 - 2.0 in. to 1.0 in. and 1.0 in. to No. 4 3 57 2.4 at 28 B(AE) 517 0.55 5.0 ± 1.5 2.0 in. to 1.0 in. and 1.0 in. to No. 4 3 57 2.4 at 28 C 658 0.49 - 0.5 to No. 4 7 4.0 at 28 C(AE) 658 0.45 7.0 ± 1.5 0.5 to No. 4 7 4.0 at 28 P 564 0.49 -b 1.0 in. to No. 4 or 0.75 to No. 4 7 67 ≤ 6.0 at b S 658 0.58 - 1.0 to No. 4 7 - P(HPC) -c 0.40 -b ≤ 0.75 in. 67 ≤ 6.0 at b A(HPC) -c 0.45 -b -c -c ≤ 6.0 at b SCC 658 0.44* - 0.75 to No. 4 67 4.0 at 28 SCC(AE) 658 0.44* 6.0 ± 1.5 0.75 to No. 4 67 4.0 at 28 Notes: a As noted in AASHTO M 43 (ASTM D448), Table 1–Standard Sizes of Processed Aggregate. b As specified in the contract documents. c Minimum cementitious materials content and coarse aggregate size to be selected to meet other performance criteria specified in the contract. *Water-to-powder ratio (W/P) is used when limestone powder is added as a filler in SCC mixtures for up to 15%. 8.3—MATERIALS 8.3.7—Air-Entraining and Chemical Admixtures Air-entraining admixtures shall conform to the requirements of AASHTO M 154 (ASTM C260). Chemical admixtures shall conform to the requirements of AASHTO M 194 (ASTM C494/C494M). Unless otherwise specified in the contract documents, only Type A, Type B, Type D, Type F, or Type G shall be used. C8.3.7 The types of chemical admixtures are as follows: Type A—Water-reducing Type B—Retarding Type D—Water-reducing and retarding Type F—Water-reducing and high-range Type G—Water-reducing, high-range, and retarding Based on the work by Morcous et al. (2015), the use of polycarboxylate-based high range water-reducing Admixtures containing chloride ion (CL) in excess of one percent by weight (mass) of the admixture shall not be used in reinforced concrete. Admixtures in excess of 0.1 percent shall not be used in prestressed concrete.

A-14 A Certificate of Compliance signed by the Manufacturer of the admixture shall be furnished to the Engineer for each shipment of admixture used in the work. Said Certificate shall be based upon laboratory test results from an approved testing facility and shall certify that the admixture meets the above specifications. If more than one admixture is used, documentation demonstrating the compatibility of each admixture with all other proposed admixtures, and the sequence of application to obtain the desired effects, shall be submitted by the Contractor. Air-entraining and chemical admixtures shall be incorporated into the concrete mix in a water solution. The water so included shall be considered to be a portion of the allowed mixing water. 8.3.8—Mineral Admixtures Mineral admixtures in concrete shall conform to the following requirements: Fly ash pozzolans and calcined natural pozzolans—AASHTO M 295 (ASTM C618) Ground granulated blast-furnace slag— AASHTO M 302 (ASTM C989) Silica fume—AASHTO M 307 (ASTM C1240) Limestone powder—AASHTO M240 (ASTM C595) Fly ash as produced by plants that utilize the limestone injection process or use compounds of sodium, ammonium, or sulfur, such as soda ash, to control stack emissions shall not be used in concrete. A Certificate of Compliance, based on test results and signed by the producer of the mineral admixture certifying that the material conforms to the above specifications, shall be furnished for each shipment used in the work. Where special materials other than those identified above are included in a concrete mix design, the properties of those materials shall be determined by methods specified in the contract documents. Ground limestone, sometimes referred to as limestone powder, can be used in Classes SCC and SCC(AE) with up to 15% replacement of the total powder content. Ground limestone shall comply with all the physical and chemical requirements specified in the contract documents. The fineness of ground limestone has a significant impact on both fresh and hardened concrete properties. C8.3.8 Pozzolans (fly ash, silica fume) and slag are used in the production of Class P(HPC) and Class A(HPC) concretes to extend the service life. Fly ash, GGBFS and limestone powder are commonly used in the production of Classes SCC and SCC(AE) to enhance the performance of the fresh and hardened concrete. Occasionally, it may be appropriate to use other materials; for example, when concretes are modified to obtain very high strengths through the introduction of special materials, such as: Silica fume, Cements other than portland or blended hydraulic cements, Proprietary high early strength cements, Ground granulated blast-furnace slag, and Other types of cementitious and/or pozzolanic materials. admixtures (HRWRA) Type F or G conforming to the requirements of ASTM C494 or ASTM C1017 is recommended for Classes SCC and SCC(AE) to achieve the required slump flow of fresh concrete. Also, the use of viscosity modifying admixtures (VMA) may be needed to achieve the required stability of fresh concrete. The dosage of these chemical admixtures varies depending on the powder constituents and content, w/p ratio, aggregate type and gradation, temperature, and mixing conditions.

A-15 8.4—PROPORTIONING OF CONCRETE 8.4.1—Mix Design 8.4.1.1—Responsibility and Criteria The Contractor shall design and be responsible for the performance of all concrete mixes used in structures. The mix proportions selected shall produce concrete that is sufficiently workable and finishable for all uses intended and shall conform to the requirements in Table 8.2.2-1 and all other requirements of this Section. For normal weight (-density) concrete, the absolute volume method, such as described in American Concrete Institute Publication 211.1, shall be used in selecting mix proportions. For Class P(HPC) with fly ash, the method given in American Concrete Institute Publication 211.4 shall be permitted. For lightweight (low-density) concrete, the mix proportions shall be selected on the basis of trial mixes, with the cement factor rather than the water/cement ratio being determined by the specified strength, using methods such as those described in American Concrete Institute Publication 211.2. For classes SCC and SCC(AE), the methods given in the American Concrete Institute Publication 237R- 07 and International Center for Aggregates Research (ICAR) Report 108-1 may be used for proportioning SCC mixtures. The mix design shall be based on the specified properties. When strength is specified, select an average concrete strength sufficiently above the specified strength so that, considering the expected variability of the concrete and test procedures, no more than one in ten strength tests will be expected to fall below the specified strength. For classes SCC and SCC(AE), the specified properties shall include workability properties such as filling ability, passing ability, and stability. Mix designs shall be modified during the course of the work when necessary to ensure compliance with the specified fresh and hardened concrete properties. For Class P(HPC) and Class A(HPC), such modifications shall only be permitted after trial batches to demonstrate that the modified mix design will result in concrete that complies with the specified concrete properties. C 8.4.1.1 Normal weight (-density) mix design refers to the American Concrete Institute (ACI), Publication 211.1, 1991. Lightweight (low-density) mix design refers to the ACI Publication 211.2, 1998. For Class P(HPC) with fly ash, the method given in ACI Publication 211.4, 1993, is permitted. In Class P(HPC) and Class A(HPC) concretes, properties other than compressive strength are also important, and the mix design should be based on specified properties rather than only compressive strength. In classes SCC and SCC(AE), properties other than compressive strength, such as filling ability, passing ability, and stability, shall be specified based on the geometric characteristics of the component as well as production and placement methods. Refer to Morcous et al. (2015) for proposed workability targets for examples of cast-in-place bridge components.

A-16 8.4.1.2—Trial Batch Tests For classes A, A(AE), P, P(HPC), SCC, SCC(AE) and A(HPC) concrete; for lightweight (low-density) concrete; and for other classes of concrete when specified in the contract documents or ordered by the mix design shall be verified by laboratory tests on trial batches. The results of such tests shall be furnished to the Engineer by the Contractor or the Manufacturer of precast elements at the time the proposed mix design is submitted. If materials and a mix design identical to those proposed for use have been used on other work within the previous year, certified copies of concrete test results from this work that indicate full compliance with these specifications may be substituted for such laboratory tests. The average values obtained from trial batches for the specified properties, such as strength, shall exceed design values by a certain amount based on variability. For compressive strength, the required average strength used as a basis for selection of concrete proportions shall be determined in accordance with AASHTO M 241 (ASTM C685/C685M). For classes SCC and SCC(AE), workability properties shall be verified by laboratory tests on trial batches. 8.4.2—Water Content For calculating the water/cement ratio of the mix, the weight (mass) of the water shall be that of the total free water in the mix, which includes the mixing water, the water in any admixture solutions, and any water in the aggregates in excess of that needed to reach a saturated-surface-dry condition. The amount of water used shall not exceed the limits listed in Table 8.2.2-1 and shall be further reduced as necessary to produce concrete of the consistencies listed in Table 8.4.2-1 at the time of placement. When Type F or G high-range, water-reducing admixtures are used, Table 8.4.2-1 slump limits may be exceeded as permitted by the Engineer. When the consistency of the concrete is found to exceed the nominal slump, the mixture of subsequent batches shall be adjusted to reduce the slump to a value within the nominal range. Batches of concrete with a slump exceeding the maximum specified shall not be used in the work. If concrete of adequate workability cannot be obtained by the use of the minimum cement content allowed, the cement and water content shall be increased without exceeding the specified water/cement ratio, or an approved admixture shall be used. For classes SCC and SCC(AE), the amount of water used shall not exceed the limits listed in Table C8.4.1.2 In Class P(HPC) and Class A(HPC) concretes, properties other than compressive strength are also important. However, if only compressive strength is specified, AASHTO M 241 (ASTM C685/C685M) provides the method to determine the required average strength. Engineer; satisfactory performance of the proposed

A-17 8.2.2-1 and shall be further reduced as necessary to achieve the specified workability targets at the time of placement as well as durability and strength requirements. Table 8.4.2.1 – Normal-Weight Concrete Slump Test Limits Type of Work Nominal Slump, in. Maximum Slump, in. Formed Elements: Sections over 12.0 in. Thick Sections 12.0 in. Thick or Less 1-3 1-4 5 5 Cast-in-Place Piles and Drilled Shafts Not Vibrated 5-8 9 Concrete Placed under Water 5-8 9 Filling for Riprap 3-7 8 8.4.4—Mineral Admixtures Mineral admixtures shall be used in the amounts specified in the contract documents. For all classes of concrete except Classes P(HPC) and A(HPC), when Types I, II, IV, or V AASHTO M 85 (ASTM C150) cements are used and mineral admixtures are neither specified in the contract documents nor prohibited, the Contractor will be permitted to replace: up to 25 percent of the required portland cement with fly ash or other pozzolan conforming to AASHTO M 295 (ASTM C618), up to 50 percent of the required portland cement with slag conforming to AASHTO M 302 (ASTM C989), or up to ten percent of the required Portland cement with silica fume conforming to AASHTO M 307 (ASTM C1240). When any combination of fly ash, slag, and silica fume are used, the Contractor will be permitted to replace up to 50 percent of the required portland cement. However, no more than 25 percent shall be fly ash and no more than ten percent shall be silica fume. The weight (mass) of the mineral admixture used shall be equal to or greater than the weight (mass) of the portland cement replaced. In calculating the water-cementitious materials ratio of the mix, the weight (mass) of the cementitious materials shall be considered to be the sum of the weight (mass) of the portland cement and the mineral admixtures. For Class P(HPC) and Class A(HPC) concrete, mineral admixtures (pozzolans or slag) shall be permitted to be used as cementitious materials with portland cement in blended cements or as a separate addition at the mixer. The amount of mineral admixture shall be determined by trial batches. The water-cementitious materials ratio shall be the ratio of the weight (mass) of water to the total cementitious materials, including the mineral admixtures. The C8.4.4 Mineral admixtures are widely used in concrete in the percentages given. For Class P(HPC) and Class A(HPC) concretes, different percentages may be used if trial batches substantiate that such amounts provide the specified properties. A 25-percent maximum of portland cement replacement is permitted for all classes, except for Classes P(HPC) and A(HPC), which have a 50-percent maximum portland cement replacement.

A-18 properties of the freshly mixed and hardened concrete shall comply with specified values. For classes SCC and SCC(AE), mineral admixtures shall be permitted to be used in blended cements or as a separate addition at the mixer. The amount of mineral admixture shall be determined by trial batches. The water-cementitious materials ratio shall be the ratio of the weight (mass) of water to the total powder materials, including the mineral admixtures. The properties of the freshly mixed and hardened concrete shall comply with specified values. Limestone powder used in classes SCC and SCC(AE) for up to 15% should be considered in the total powder content. Several studies have indicated that there is a synergistic effect of ground limestone that is reacting with the C3A in the system to enhance the reactivity of the remaining constituents, such as cement and fly ash (Cost et al., 2012; Beeralingegowda and Gundakalle, 2013; and Bucher, 2009). 8.5—MANUFACTURE OF CONCRETE The production of ready-mixed concrete and concrete produced by stationary mixers shall conform to the requirements of AASHTO M 157 and the requirements of this Article. 8.5.4—Batching and Mixing Concrete 8.5.4.1—Batching The size of the batch shall not exceed the capacity of the mixer as guaranteed by the Manufacturer or as determined by the Standard Requirements of the Associated General Contractors of America. For classes SCC and SCC(AE), the maximum size of the batch shall not exceed 80% of the mixer capacity due to the relatively high fluidity of the concrete. The measured materials shall be batched and charged into the mixer by means that will prevent loss of any materials due to effects of wind or other causes. 8.5.4.2—Mixing The concrete shall be mixed only in the quantity required for immediate use. Mixing shall be sufficient to thoroughly intermingle all mix ingredients into a uniform mixture. Concrete that has developed an initial set shall not be used. Retempering concrete shall not be permitted. For other than transit-mixed concrete, the first batch of concrete materials placed in the mixer shall contain a sufficient excess of cement, sand, and water to coat the inside of the drum without reducing the required mortar content of the mix. When mixer performance tests as described in AASHTO M 157 are not made, the required mixing time for stationary mixers shall be not less than 90 s nor more than 5 min. The minimum drum revolutions for transit mixers at the mixing speed recommended by the Manufacturer shall not be less than 70 and not less than that recommended by the Manufacturer. The timing device on stationary mixers shall be equipped with a bell or another suitable warning device adjusted to give a clearly audible signal each time the lock is released. In case of failure of the timing device, C8.5.4.2 For classes SCC and SCC(AE), adjustments to the mixing time and/or energy may be necessary to ensure sufficiency and uniformity of the mixtures. Trial batches might be needed to determine these adjustments.

A-19 the Contractor shall be permitted to operate the mixer while the timing device is being repaired, provided he furnishes an approved timepiece equipped with minute and second hands. If the timing device is not placed in good working order within 24 h, further use of the mixer shall be prohibited until repairs are made. For small quantities of concrete needed in emergencies or for small noncritical elements of the work, concrete may be hand-mixed using methods approved by the Engineer. Between uses, any mortar coating inside of mixing equipment which sets or dries shall be cleaned from the mixer before use is resumed. 8.7—HANDLING AND PLACING CONCRETE 8.7.1—General Concrete shall be handled, placed, and consolidated by methods that will not cause segregation of the mix and will result in a dense homogeneous concrete that is free of voids and rock pockets. The methods used shall not cause displacement of reinforcing steel or other materials to be embedded in the concrete. Concrete shall be placed and consolidated prior to initial set and in no case more than 1.5 h after the cement was added to the mix. Concrete shall not be retempered. For Class SCC and Class SCC(AE), concrete shall not be consolidated by any mechanical means. Concrete shall not be placed until the forms, all materials to be embedded, and, for spread footings, the adequacy of the foundation material, have been inspected and approved by the Engineer. All mortar from previous placements, debris, and foreign material shall be removed from the forms and steel prior to commencing placement. The forms and subgrade shall be thoroughly moistened with water immediately before concrete is placed against them. Temporary form spreader devices may be left in place until concrete placement precludes their need, after which they shall be removed. Placement of concrete for each section of the structure shall be done continuously without interruption between planned construction or expansion joints. The delivery rate, placing sequence, and methods shall be such that fresh concrete is always placed and consolidated against previously placed concrete before initial set has occurred in the previously placed concrete. During and after placement of concrete, care shall be taken not to injure the concrete or break the bond with reinforcing steel. Workers shall not walk in fresh concrete. Platforms for workers and equipment shall not be supported directly on any reinforcing steel. Once the concrete is set, forces shall not be applied to the forms or to reinforcing bars which project from the C8.7.1 For classes SCC and SCC(AE), limited mechanical consolidated (e.g., vibration) may be applied to the surface of a placed batch immediately before placing the next batch when concrete placement is interrupted for an extended period of time (e.g., 20 minutes) to avoid formation of joints or pour lines (lift lines) within monolithic pours.

A-20 concrete until the concrete is of sufficient strength to resist damage. 8.7.2—Sequence of Placement 8.7.2.2—Superstructures Unless otherwise permitted, no concrete shall be placed in the superstructure until substructure forms have been stripped sufficiently to determine the character of the supporting substructure concrete. Concrete for T-beam or deck girder spans whose depth is less than 4.0 ft may be placed in one continuous operation or may be placed in two separate operations; first, to the top of the girder stems, and second, to completion. For T-beam or deck girder spans whose depth is 4.0 ft or more, and unless the falsework is non-yielding, such concrete shall be placed in two operations, and at least five days shall elapse after placement of stems before the top deck slab is placed. Concrete for box girders may be placed in two or three separate operations consisting of bottom slab, girder stems, and top slab. In either case, the bottom slab shall be placed first and, unless otherwise permitted by the Engineer, the top slab shall not be placed until the girder stems have been in place for at least five days C8.7.2.2 For classes SCC and SCC(AE) used in tub or box girders, concrete may be placed in one continuous operation by placing it from one location and allowing it to flow and fill the bottom slab and stems of the girder. 8.7.3—Placing Methods 8.7.3.1—General Concrete shall be placed as nearly as possible in its final position, and the use of vibrators for extensive shifting of the weight (mass) of fresh concrete will not be permitted. Concrete shall be placed in horizontal layers of a thickness not exceeding the capacity of the vibrator to consolidate the concrete and merge it with the previous lift. In no case shall the depth of a lift exceed 2.0 ft. This requirement does not apply to self-consolidating concrete (SCC). The rate of concrete placement shall not exceed that assumed for the design of the forms as corrected for the actual temperature of the concrete being placed. When placing operations would involve dropping the concrete more than 5.0 ft, the concrete shall be dropped through a tube fitted with a hopper head or through other approved devices, as necessary to prevent segregation of the mix and spattering of mortar on steel and forms above the elevation of the lift being placed. This requirement shall not apply to cast-in- place piling when concrete placement is completed before initial set occurs in the first placed concrete. C8.7.3.1 Based on the work by Morcous et al. (2015), the free-flow distance of SCC shall not exceed 33 ft in simple sections (i.e., thick elements with one directional flow) and 20 ft in complex sections (i.e., intricate shape or thin elements). Based on the work by Morcous, et al. (2015), the free-fall height of SCC proportioned with high segregation resistance shall not exceed 15 ft, otherwise, the free-fall height shall not exceed 5 ft.

A-21 8.7.3.2—Equipment All equipment used to place concrete shall be of adequate capacity and designed and operated so as to prevent segregation of the mix or loss of mortar. Such equipment shall not cause vibrations that might damage the freshly placed concrete. No equipment shall have aluminum parts which come in contact with the concrete. Between uses, the mortar coating inside of placing equipment which sets or dries out shall be cleaned from the equipment before use is resumed. Chutes shall be lined with smooth watertight material and, when steep slopes are involved, shall be equipped with baffles or reverses. Concrete pumps shall be operated such that a continuous stream of concrete without air pockets is produced. When pumping is completed, the concrete remaining in the pipeline, if it is to be used, shall be ejected in such a manner that there will be no contamination of the concrete or separation of the ingredients. Conveyor belt systems shall not exceed a total length of 550.0 linear ft, measured from end to end of the total assembly. The belt assembly shall be so arranged that each section discharges into a vertical hopper arrangement to the next section. To keep segregation to a minimum, scrapers shall be situated over the hopper of each section so as to remove mortar adhering to the belt and to deposit it into the hopper. The discharge end of the conveyor belt system shall be equipped with a hopper and a chute or suitable deflectors to cause the concrete to drop vertically to the deposit area. 8.7.4—Consolidation All concrete, except concrete placed under water, SCC, and concrete otherwise exempt, shall be consolidated by mechanical vibration immediately after placement. Except as noted herein, vibration shall be internal. External form vibrators may be used for thin sections when the forms have been designed for external vibration. Vibrators shall be of approved type and design and of a size appropriate for the work. They shall be capable of transmitting vibration to the concrete at frequencies of not less than 75 Hz. The Contractor shall provide a sufficient number of vibrators to properly compact each batch of concrete immediately after it is placed in the forms. The Contractor shall also have at least one spare vibrator immediately available in case of breakdown. Vibrators shall be manipulated so as to thoroughly work the concrete around the reinforcement and embedded fixtures and into the corners and angles of the forms. Vibration shall be applied at the point of deposit and in the area of freshly deposited concrete. The vibrators shall be inserted and withdrawn out of C8.7.3.2 Despite its high fluidity, SCC flow is fundamentally different from that of conventionally vibrated concrete (sheared layers versus large plug flow), which may require adjustments to minimize the risk of blockage in the pump line. SCC may require the use of a larger pump line diameter (depending on its viscosity) than that required for high slump conventionally vibrated concrete containing the same aggregate type and size. C8.7.4 Limited mechanical consolidated (e.g., vibration) may be applied to the surface of a placed batch immediately before placing the next batch when concrete placement is interrupted for an extended period of time (e.g., 20 minutes) to avoid formation of joints or pour lines (lift lines) within monolithic pours.

A-22 the concrete slowly. The vibration shall be of sufficient duration and intensity to thoroughly consolidate the concrete but shall not be continued so as to cause segregation. Vibration shall not be continued at any one point to the extent that localized areas of grout are formed. Application of vibrators shall be at points uniformly spaced and not farther apart than 1.5 times the radius over which the vibration is visibly effective. Vibration shall not be applied either directly to, or through the reinforcement to, sections or layers of concrete which have hardened to the degree that the concrete ceases to be plastic under vibration. Vibrators shall not be used to transport concrete in the forms. Where immersion-type vibrators are used to consolidate concrete around epoxy-coated reinforcing steel, the vibrators shall be equipped with rubber or other nonmetallic coating. Vibration shall be supplemented by such spading as is necessary to ensure smooth surfaces and dense concrete along form surfaces and in corners and locations impossible to reach with the vibrators. When approved by the Engineer, concrete for small noncritical elements may be consolidated by the use of suitable rods and spades.