Self-Consolidating Concrete for Cast-in-Place Bridge Components (2016) / Chapter Skim
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Pages 63-84
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From page 63... ...
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)
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From page 64... ...
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.
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From page 65... ...
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.
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From page 66... ...
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.
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From page 67... ...
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)
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From page 68... ...
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)
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From page 69... ...
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)
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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.)
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From page 71... ...
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.
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From page 72... ...
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.
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From page 73... ...
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 .....................................................................
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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.
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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.
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From page 76... ...
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.
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From page 77... ...
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.
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A-16 8.4.1.2 -- Trial Batch Tests For classes A, A(AE)
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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.
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A-18 properties of the freshly mixed and hardened concrete shall comply with specified values. For classes SCC and SCC(AE)
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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.
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From page 82... ...
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.
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From page 83... ...
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.
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From page 84... ...
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.
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