Self-Consolidating Concrete for Precast, Prestressed Concrete Bridge Elements (2009) / Chapter Skim
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Pages 12-21
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From page 12... ...
Limited published data are available on relationships between flexural strength and compressive strength of SCC, and applicability of the various code models to SCC need to be validated. Typically, SCC mixtures are proportioned with higher binder content, lower coarse aggregate volume, and smaller MSA, which increase thermal, autogenous, and drying shrinkage, and creep leading to high loss of prestress and excessive deflections and elastic shortening.
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From page 13... ...
Details of this work are discussed below. Phase 1: Test Methods and Acceptance Criteria for SCC This work included: • A parametric study of various concrete mixture parameters and constituent materials to help develop recommendations for mix design of SCC for precast, prestressed applications; • Evaluations of the effect of MSA, aggregate and binder types, and w/cm on workability and compressive strength development of SCC mixtures suitable for precast structural applications; • Comparison of workability test methods that can be used for mix design and quality control of SCC, and suggestion of performance specifications; and • Correlation of key workability responses to basic rheological parameters (in particular, plastic viscosity)
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From page 14... ...
Mixture Proportioning Guidelines. Based on the results of the parametric study, and consideration of the effects of w/cm, binder type, and nominal size and type of coarse aggregate on workability characteristics and development of compressive strength, guidelines for the proportioning of SCC for use in precast, prestressed applications were proposed.
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From page 15... ...
Experimental program of parametric investigation. SCC behavior Property Test Method Test age Number of samples per mixture Comments Rheology Yield stress and plastic viscosity Modified Tattersall MK III rheometer 10 & 40 minutes Not applicable Filling ability Slump flow and T-50(upright cone position)
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From page 16... ...
A low w/cm was included for better mechanical performance and the higher w/cm was included for better workability. Type III binder with 20% of Class F fly ash replacement was chosen over Type III binder with 30% slag because of its better overall performance in terms of workability and compressive strength development.
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From page 17... ...
Test results were compared with the provisions for elasticity modulus, compressive strength, creep, drying shrinkage, and bond stipulated in several codes (AASHTO LRFD Specifications [2004 and 2007] ; Precast/Prestressed Concrete Institute (PCI)
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From page 18... ...
SCC behavior Property Test method Test age Number of samples per mixture Comments Rheology Yield stress and plastic viscosity and thixotropy Modified Tattersall MK III rheometer 10 & 40 minutes Not applicable Filling ability Slump flow, T-50 (upright cone position) ASTM C 1611 10 & 40 minutes Not applicable J-Ring ASTM C 1621 Passing ability & filling capacity L-box, caisson filling capacity 10 & 40 minutes Not applicable Surface settlement Over the first 24 hours 1 Column segregation ASTM C 1610 1 Visual stability index ASTM C 1611 Not applicable Stability Stability of air*
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From page 19... ...
Phase 3: Structural Performance of Full-Scale AASHTO-Type II Girders The structural performance of full-scale AASHTO precast, prestressed bridge girders constructed with selected SCC mixtures was investigated to evaluate the applicability of current design provisions (AASHTO and PCI) and to recommend appropriate modifications to the AASHTO LRFD Specifications.
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From page 20... ...
(12.5 mm) crushed aggregate for all mixtures SCC behavior Property Test method Test age Number of samples per mixture Size/volume of specimen Comments Rheology Yield stress, plastic viscosity Modified Tattersall MK III rheometer At arrival & after casting Not Not Not applicable applicable applicable Not applicable Not applicable 0.89 ft3 (25 l)
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From page 21... ...
. SCC behavior Property Test method Test age Number of samples per mixture Size/volume of specimen At release 3 steam cured 3 air cured 7 days 3 moist cured d 3 air curede 28 days 3 moist cured d 3 air curede 56 days 3 moist cured d 3 air curede Compressive strength AASHTO T 22 At shear testing 3 moist curedd 3 air curede 4 8 in.
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