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13 shrinkage, and thermal contraction have to be considered in · Factors affecting mechanical properties and structural the mix design process and in the structural detailing of the performance, prestressed element. · Factors affecting visco-elastic properties, and Studies have shown that the scatter between measured and · Durability characteristics. predicted drying shrinkage values is greater in the case of SCC than that for normal concrete. Experimental shrinkage strains Experimental Work Plan for SCC were found to be larger than those estimated by var- ious prediction models [Byun et al., 1998]. Also, comparison The experimental program was conducted in three phases. of experimental creep data to those obtained from major Phase I addressed test methods and acceptance criteria; Phase creep-prediction models indicated differences. Work is re- II addressed mixture proportioning and material character- quired to compare creep and shrinkage data of SCC mixtures istics; and Phase III addressed structural performance of full- made with representative mix designs and the material con- scale girders. Details of this work are discussed below. stituents available in the United States with those obtained from prediction models. Phase 1: Test Methods and Acceptance Criteria The stability of SCC is a key property in ensuring uniform for SCC mechanical properties and adequate performance of precast, This work included: prestressed concrete bridge girders. Properly designed SCC mixtures can exhibit uniform distribution of in-situ compres- · A parametric study of various concrete mixture parameters sive strength. Bond strength and its uniformity along the height and constituent materials to help develop recommendations of the girders can be influenced by flow properties of the SCC, for mix design of SCC for precast, prestressed applications; grading of the aggregate, and content of fines. Some studies · Evaluations of the effect of MSA, aggregate and binder have found that bond strength of reinforcement to SCC can types, and w/cm on workability and compressive strength be lower than that to normal concrete [Koning et al., 2001; development of SCC mixtures suitable for precast structural Hegger et al., 2003]. Other studies, however, have shown that applications; for a given compressive strength, reinforced concrete members · Comparison of workability test methods that can be used made with SCC can develop higher bond strength than in the for mix design and quality control of SCC, and suggestion case of normal concrete [Dehn et al., 2000; Chan et al., 2003]. of performance specifications; and Bond strength that can be developed between SCC and pre- · Correlation of key workability responses to basic rheological stressed strands and its uniformity along the height of cast wall parameters (in particular, plastic viscosity). elements were investigated in this project. The parametric study of 24 nonair-entrained SCC mixtures The structural design concerns related to the use of SCC (No. 1 through 24 in Table 4) was conducted to evaluate the for constructing prestressed girders include the likely lower influence of binder type, w/cm, and coarse aggregate type and modulus and greater shrinkage of SCC and the possible larger nominal size on workability and compressive strength devel- prestress losses and the reduced shear resistances resulting opment of SCC mixtures designated for the construction of from the use of a smaller maximum aggregate size or a smaller precast, prestressed AASHTO girders. These mixtures were volume of coarse aggregate. prepared using either crushed aggregate or gravel of three dif- ferent MSA [3/4, 1/2, and 3/8 in. (12, 19.5, and 9.5 mm)], w/cm of 2.2 Research Approach 0.33 and 0.38, and three binder compositions (Type III cement with 30% slag replacement, Type I/II cement, and Type III Literature Review cement with 20% Class F fly ash). Three air-entrained SCC As a part of the project, an extensive literature review of mixtures (No. 25 through 27 in Table 4) were prepared with factors affecting performance of SCC in structural applications low w/cm to obtain an initial air volume of 4% to 7%. was carried out (details of the literature review are summarized Three SCC mixtures (No. 28 through 30) similar to mix- in Attachment D). The literature review pertained to precast, tures No. 1 through 3, having relatively low filling ability prestressed SCC, including: (deformability) with slump flow values of 23.5 to 25.0 in. (600 to 640 mm), and three other mixtures (No. 31 through 33) · Test methods and acceptance criteria of fresh characteristics similar to mixtures No. 4 through 6, presenting relatively of SCC, high slump flow of 28.0 to 30.0 in. (710 to 760 mm), were · Requirements for constituent materials and mix design prepared to evaluate the effect of fluidity level on filling abil- considerations, ity, passing ability, filling capacity, stability, and compressive · Production and placement issues, strength development.
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14 Table 4. Parametric experimental program. Mixture No. Aggregate type and MSA Type and content of binder w/cm Crushed Crushed Crushed Gravel Type I/II Type III + Type III + Type 3 809 pcy 30% Slag 20% fly ash ¾ in. 8 in. ½ in. ½ in. 0.33 0.38 (19 mm) (9.5 mm) (12.5 mm) (12.5 mm) (480 775 pcy 775 pcy kg/m ) (460 kg/m3) (460 kg/m3) 3 1 x x x 2 x x x 3 x x x 4 x x x 5 x x x 6 x x x Nonair-entrained (AE) concrete 7 x x x 8 x x x 9 x x x 10 x x x 11 x x x 12 x x x 13 x x x 14 x x x 15 x x x 16 x x x 17 x x x 18 x x x 19 x x x 20 x x x 21 x x x 22 x x x 23 x x x 24 x x x concrete Air entrainment of 4%7% and slump flow of 26.027.5 in. (660700 mm) 25- AE 27 w/cm of 0.33, Type III + 20% Class F fly ash, crushed aggregate with MSA of ½ in. (12.5 mm) 28- Low filling ability, slump flow of 23.525.0 in. (600635 mm) Non-AE concrete 30 w/cm of 0.33, Type III + 30% slag, crushed aggregate with MSA of ¾ in. (19 mm) 31- High filling ability, slump flow of 28.030.0 in. (710760 mm) 33 w/cm of 0.38, Type III + 30% slag, crushed aggregate with MSA of ¾ in. (19 mm) Two levels of slump flow consistency for evaluation of repeatability: 25.0 and 27.5 in. 34- 43 (635 and 700 mm) w/cm of 0.38, Type I/II, crushed aggregate with MSA of ½ in. (12.5 mm) Notes Sandtototal aggregate ratio (S/A) is fixed at 0.50, by volume. PC-based HRWRA (AASHTO M 194, Type F) and air-entraining admixture (AASHTO M 154) are added. Limestone crushed coarse aggregate. In addition, 10 SCC mixtures (No. 34 through 43) with ulus of elasticity. For the determination of strength develop- proportions similar to those of mixture No. 16 were used to ment beyond 18 hours, the samples were air cured in the evaluate the repeatability of workability tests. Each concrete molds under wet burlap at 73 ± 4°F (23 ± 2°C) for 1 day be- mixture was tested for several workability characteristics, com- fore demolding and storing in a moist-curing chamber. pressive strength, and modulus of elasticity as indicated in Table 5. The test methods that were used to evaluate the work- Mixture Proportioning Guidelines. Based on the results ability of SCC are described in Attachment D. of the parametric study, and consideration of the effects of Several 4 × 8 in. (100 × 200 mm) concrete cylinders were w/cm, binder type, and nominal size and type of coarse aggre- cast within 10 minutes to evaluate the compressive strength gate on workability characteristics and development of com- and modulus of elasticity at 18 hours of age. The cylinders pressive strength, guidelines for the proportioning of SCC for were cast in one lift without any mechanical consolidation. use in precast, prestressed applications were proposed. The specimens were demolded at 16 hours of age and tested at 18 hours. Some of the specimens were cured in the labora- Comparison of Responses of Various Test Methods. tory at 73 ± 4°F (23 ± 2°C) under wet burlap, while others Correlations among the various test results were used to iden- were steam cured to determine early-age strength and mod- tify advantages and limitations of these methods. Linear and
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15 Table 5. Experimental program of parametric investigation. Number of SCC Test Test Property samples per Comments behavior Method age mixture Modified Yield stress and 10 & 40 Rheology Tattersall MK Not applicable plastic viscosity minutes III rheometer Slump flow and T-50 AASHTO 10 & 40 Filling ability Not applicable (upright cone position) T 119 minutes J-Ring, L-box, Passing ability, ASTM C 1621 10 & 40 V-funnel flow, and Not applicable filling capacity (for J-Ring) minutes caisson filling capacity Over the Surface settlement first 24 1 hours 10 Column segregation ASTM C 1610 1 Stability minutes Visual stability index ASTM C 1611 Not applicable AASHTO Over 40 Stability of air* Not applicable T 152 minutes 3 air cured 18 hours 3 steam cured Air curing at 50 ± 4% RH and 73 ± 4°F AASHTO (23 ± 2°C) Compressive strength 28 days 3 moist cured T 22 Mechanical Moist curing at properties 100% RH and 73 ± 56 days 3 moist cured 4°F (23 ± 2°C) Steam curing only for 16 hours Modulus of elasticity ASTM C 469 18 hours 2 steam cured * Agitation of concrete between 10 and 40 minutes at 6 rpm multiple regression analysis were used to relate the responses using different batches. Each test was performed by different of various tests. operators. The data were used to develop precision statements. Appropriate test methods that can be used to assess the workability of SCC in the laboratory and at the precast plant Phase 2: Effect of Mixture Proportioning and for quality control were proposed. Ranges of acceptance val- Material Characteristics on Key Parameters ues for these test methods were established. Non-standard Affecting Fresh and Hardened Properties test methods recommended for adoption as standard test methods are provided in Attachment C. Limited information is available on the properties of hard- ened SCC mixtures typically used in precast, prestressed Relationship Between Workability Measurements and structural applications. Such properties can vary with the Rheological Properties. The various test responses were characteristics of constituent materials, including aggregate related to plastic viscosity of the concrete using a concrete properties, type and composition of binder, and admixture rheometer. "Workability boxes" identifying combinations of combinations. Mixture composition and curing conditions rheological parameters necessary to secure adequate stability necessary to secure the targeted strength for release of the pre- of SCC were established for the SCC mixtures evaluated. stressing also have a marked effect on engineering properties and durability of the SCC. Repeatability of Test Results. One mixture that exhib- The experimental work included nonair-entrained and air- ited good fluidity retention was used at two different slump entrained SCC mixtures. The targeted compressive strength at flow levels (low and high) to establish the repeatability of the release of the prestressing strands for structural AASHTO-type workability test methods. Each test was conducted five times, girders was set at 5,000 psi (34.5 MPa) after 18 hours of casting.
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16 The targeted 56-day compressive strength of the SCC mix- included binder content, binder type, w/cm, S/A, and dosage tures that were investigated in this study was 8,000 to 10,000 of VMA. In total, 16 SCC mixtures were selected to form a psi (55.2 to 69 MPa) determined on 4 × 8 in. (100 × 200 mm) factorial design with the following five main factors: cylinders moist cured at 100% relative humidity (RH) and · Binder content: 742 and 843 lb/yd3 (440 and 500 kg/m3) 73 ± 4°F (23 ± 2°C). The specification of 56-day compressive · w/cm: 0.34 and 0.40 strength is important when fly ash or ground granulated · Dosage of thickening-type VMA: 0 and moderate dosage blast-furnace slag is incorporated in the SCC mixture because · Binder type: Type I/II and Type III cement with 20% Class of the pozzolanic reaction. F fly ash · S/A: 0.46 and 0.54, by volume NonAir-Entrained Concrete Mixtures. The experimen- tal factorial design presented in Table 6 was selected to eval- The magnitude of these variables was selected to cover a uate the influence of mixture proportioning and constituent wide range of mixture ingredients and designs used in the material characteristics on the properties that are critical to United States. The w/cm and binder type were selected based the performance of precast, prestressed concrete girders. The on the results of the parametric study. A low w/cm was in- effect of primary ingredients and mix design parameters on key cluded for better mechanical performance and the higher workability and engineering properties of SCC was evaluated. w/cm was included for better workability. Type III binder with Based on the literature review and findings of the parametric 20% of Class F fly ash replacement was chosen over Type III study, four mixture proportioning items and one ingredient binder with 30% slag because of its better overall performance type were considered in the experimental design. The factors in terms of workability and compressive strength development. Table 6. Factorial experimental program. Coded values Absolute values Binder type Binder type Mix Type (kg/m3) Binder Binder VMAa lb/yd3 VMA w/cm w/cm No. S/Ab S/A 1 -1 -1 -1 -1 1 742 (440) 0.34 0 I/II 0.54 2 -1 -1 -1 1 -1 742 (440) 0.34 0 IIIc 0.46 3 -1 -1 1 -1 -1 742 (440) 0.34 moderate I/II 0.46 SCC (2627.6 in. [660700 mm] slump flow) 4 -1 -1 1 1 1 742 (440) 0.34 moderate III 0.54 Fractional factorial points 5 -1 1 -1 -1 -1 742 (440) 0.40 0 I/II 0.46 6 -1 1 -1 1 1 742 (440) 0.40 0 III 0.54 7 -1 1 1 -1 1 742 (440) 0.40 moderate I/II 0.54 8 -1 1 1 1 -1 742 (440) 0.40 moderate III 0.46 9 1 -1 -1 -1 -1 843 (500) 0.34 0 I/II 0.46 10 1 -1 -1 1 1 843 (500) 0.34 0 III 0.54 Non-AE concrete 11 1 -1 1 -1 1 843 (500) 0.34 moderate I/II 0.54 12 1 -1 1 1 -1 843 (500) 0.34 moderate III 0.46 13 1 1 -1 -1 1 843 (500) 0.40 0 I/II 0.54 14 1 1 -1 1 -1 843 (500) 0.40 0 III 0.46 15 1 1 1 -1 -1 843 (500) 0.40 moderate I/II 0.46 16 1 1 1 1 1 843 (500) 0.40 moderate III 0.54 0 0 0 0 0 792 (470) 0.37 moderate I/II-III 0.50 Central points 0 0 0 0 0 792 (470) 0.37 moderate I/II-III 0.50 0 0 0 0 0 792 (470) 0.37 moderate I/II-III 0.50 w/cm = 0.34, Type I/II cement, ½ in. (12.5 mm) crushed aggregate 17 Normal consistency mixtures with 6 in. (150 mm) slump HPC w/cm = 0.38, Type III + 20% Class F fly ash, ½ in. (12.5 mm) crushed 18 aggregate Normal consistency mixtures with 6 in. (150 mm) slump concrete SCC 19 Air-entrainment of 4% to7% and slump flow of 2627.6 in. (660700 mm) AE 22 Mixtures selected based on performance of nonair-entrained concrete a Thickening-type VMA b Crushed aggregate with MSA of ½ in. (12.5 mm) and natural sand c Type III cement + 20% Class F fly ash
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17 The crushed coarse aggregate with a MSA of 1/2 in. (12.5 mm) using a mechanical calibration instrument prior to use. Drop was used because it offers better performance in terms of in lateral pressure was monitored until pressure cancellation workability and strength development than gravel of similar (results are presented in Attachment D). MSA or crushed aggregate with 3/8 or 3/4 in. (9.5 or 19 mm). Three replicate central points were prepared to estimate the Temperature Rise. Temperature rise was measured in a degree of experimental error for the modeled responses. In 6 × 12 in. (150 × 300 mm) concrete cylinder that was inserted addition to the 16 SCC mixtures, two HPC mixtures of nor- at the center of a styrofoam box measuring 3.3 × 3.3 × 3.3 ft mal consistency were evaluated. (1 × 1 × 1 m). Three thermo-couples were installed inside the It should be noted that other mixture proportioning and concrete cylinders--one in the center of the cylinder, one in material parameters (e.g., coarse aggregate shape and MSA, the middle height of the inner side of the cylinder, and one in combined aggregate gradation, and sand type and fineness the top of the inner side of the cylinder--to determine the modulus) can also influence the performance of SCC. How- temperature rise under semi-adiabatic conditions. ever, only the most relevant factors were considered in the Autogenous Shrinkage. Autogenous shrinkage was meas- experimental program, as indicated in Table 7. ured on 3 × 3 × 11.8 in. (75 × 75 × 285 mm) prisms. The prisms Air-Entrained Concrete Mixtures. Four SCC mixtures were sealed immediately after removal from the molds at were prepared to evaluate the effect of air-entrainment (4% 18 hours of age and kept at 73 ± 4°F (23 ± 2°C) until the end of to 7%) on fresh properties, fluidity retention, strength devel- testing. Autogenous shrinkage was monitored using embedded opment, flexural strength, elastic modulus, air-void spacing fac- vibrating wire strain gages until stabilization, which occurred tor, and frost durability. These mixtures were selected based on after approximately 3 weeks of age. The autogenous shrink- results of the nonair-entrained concrete mixtures and were age was obtained by subtracting the total shrinkage from prepared with a selected combination of thickening-type VMA, thermal deformation. A linear thermal expansion coefficient polycarboxylate-based HRWRA, and a fixed S/A. Two concrete of 6.4 µin./in./°F (11.5 µm/m/°C) was assumed for adjusting mixtures were prepared using two different binder types. vibrating wire gage readings. The thermal expansion coefficient of the concrete was determined from the slope of the total The initial slump flow of the 16 fractional factorial and three deformation versus temperature curve of concrete prisms central SCC mixtures was 26.0 to 27.5 in. (660 to 700 mm). subjected to controlled temperature changes. Two prisms were The targeted release compressive strength after 18 hours of initially immersed in water at the approximate temperature steam curing and 56-day compressive strength were 5,000 psi of 122°F (50°C). Once the temperature of the specimens was (34.5 MPa) and 8,000 to 10,000 psi (55 to 69 MPa), respec- stabilized, the water was allowed to cool down to approxi- tively. The compressive strength was determined on 4 × 8 in. mately 68°F (20°C). The resulting deformations were used to (100 × 200 mm) cylinders. For 56-day compressive strength, estimate the coefficient of thermal expansion/contraction of the specimens were stored at 100% RH and 73 ± 4°F (23 ± 2°C) the concrete. until the time of testing. The change in temperature in the chamber and in 4 × 8 in. (100 × 200 mm) reference cylinders Drying Shrinkage and Creep. Six 6 × 12 in. (150 × 300 mm) during steam curing are presented in Attachment D. test specimens were cast to monitor creep and drying shrinkage. Test results were compared with the provisions for elastic- The specimens were steam cured until the age of 16 hours and ity modulus, compressive strength, creep, drying shrinkage, were then demolded. The ends of creep cylinders were ground and bond stipulated in several codes (AASHTO LRFD Spec- and external studs were installed for deformation measure- ifications [2004 and 2007]; Precast/Prestressed Concrete In- ments. A digital-type extensometer was used to determine stitute (PCI) Bridge Design Manual 1997; ACI 209, ACI 318, drying shrinkage and creep. Creep and shrinkage testing started CEB-FIP MC90, etc.). at the age of 18 hours. The applied creep loading corresponded to 40% of the 18-hour compressive strength of the steam-cured Formwork Pressure. The initial maximum pressure concrete cylinders. Creep and shrinkage specimens were kept exerted by SCC and HPC was evaluated by casting concrete in a temperature-controlled room at 73 ± 4°F (23 ± 2°C) and in rigid polyvinyl chloride (PVC) column measuring 3.6 ft 50% ± 4% relative humidity. Initial elastic deformations were (1.1 m) in height and 7.9 in. (200 mm) in diameter at a rate measured directly after loading; creep and drying shrinkage of 13 to 16 ft/h (4 to 5 m/h). Pressure sensors were installed at deformations were monitored for 11 months; the long-term 2, 10, and 18 in. (50, 250, and 450 mm) from the bottom of the deformations were all stabilized at that time. pressure decay tube. The sensors were set flush with the inner surface of the PVC column; the drilled holes through the PVC Pull-out Bond Strength. Pull-out testing of prestressing tubing were sealed to avoid leakage. The pressure sensors had strands was conducted for five SCC mixtures and one conven- a capacity of 25 psi (170 kPa), can operate over a temperature tional concrete mixture. The SCC mixtures were proportioned range of -58°F to 212°F (-50°C to 100°C), and were calibrated with different viscosity and static stability levels. Tests were
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18 Table 7. Factors considered in the testing program. Number of SCC Test Test Property samples Comments behavior method age per mixture Modified Yield stress and plastic Tattersall 10 & Rheology Not applicable viscosity and thixotropy MK III 40 minutes rheometer Slump flow, T-50 ASTM 10 & Filling ability Not applicable (upright cone position) C 1611 40 minutes ASTM Passing ability J-Ring C 1621 10 & & filling Not applicable L-box, caisson filling 40 minutes capacity capacity Over the Surface settlement 1 first 24 hours ASTM Column segregation 1 C 1610 Stability ASTM Visual stability index Not applicable C 1611 AASHTO Over Stability of air* Not applicable T 152 40 minutes 3 air cured 18 hours 3 steam cured Air curing: 50 ± AASHTO 7 days 3 moist cured 4% RH, 73 ± 4°F Compressive strength (23 ± 2°C) T 22 28 days 3 moist cured 56 days 3 moist cured Moist curing: 2 air cured 100% RH, 73 ± 4°F Mechanical 18 hours 2 steam cured (23 ± 2°C) properties ASTM Modulus of elasticity 28 days 2 moist cured C 469 Steam curing: 56 days 2 moist cured only for 14 hours 7 days 3 moist cured (refer to AASHTO Flexural strength 28 days 3 moist cured Attachment D) T 97 56 days 3 moist cured Over the first Semi-adiabatic Temperature rise 1 Hydration 24 hours conditions kinetics AASHTO Setting time 1 T 197 Initial formwork Rate of rise of 13.1 Form pressure 2 to 4 hours 1 pressure to 16.4 ft/h (4 to characteristics Variation of pressure First 24 hours 1 5 m/h) with time Embedded Over 10 to Autogenous shrinkage vibrating 2 Sealed prisms 14 days wire gages Visco-elastic Same curing AASHTO Over properties Drying shrinkage 3 regime used for T 160 11 months release strength ASTM Over Loading at release Creep 3 C 512 11 months time ASTM Starting at 56 Air-void parameters 1 C 457 days Frost durability AASHTO Freezing and thawing Starting at 56 T 161, 2 resistance days Method A Air curing: at 50 ± Pull-out load-end slip Bond strength 56 days 5 SCC & 1 HPC 4% RH, 73 ± 4°F response (23 ± 2°C) * Agitation of concrete between 10 and 40 minutes at 6 rpm
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19 conducted to determine the maximum pull-out load versus the tions, transfer lengths, cambers, flexural cracking, shear crack- end slip response of strands that were horizontally embedded ing, and shear strengths. More details on the construction and in experimental wall elements. In total, 16 Grade 270, 0.6 in. testing of these girders are given in Attachment D. (15.2 mm) diameter low-relaxation prestressing strands Two nonair-entrained SCC mixtures of different compres- were embedded at four heights in 60.6 H × 84.6 L × 7.9 W in. sive strength levels were used to cast two full-scale AASHTO- (1,540 H × 2,150 L × 200 W mm) wall elements. Rigid plastic Type II girders. One mixture had target 56-day compressive sheathing was tightly attached to the outer end of each strand strength of 8,000 (55 MPa) and release strength of 5,000 psi near the loaded end as bond breaker to reduce secondary con- (34.5 MPa) and the other had target compressive and release fining stresses along the bonded region. strengths of 10,000 psi (69 MPa) and 6,250 psi (43 MPa), The formwork was removed 1 day after concrete casting. respectively. Two additional girders were cast using HPC The concrete wall elements were then maintained under wet mixtures with target 56-day compressive strengths of 8,000 curing until 7 days of age before being air-dried. Pull-out tests and 10,000 psi (55 and 69 MPa). The HRWRA dosages for the were conducted at 56 days of age. The pull-out load was ap- HPC and SCC mixtures were adjusted to obtain a slump of plied gradually and recorded using a load cell; the net slip was 6.3 ± 0.8 in. (160 ± 20 mm) and a slump flow of 26.8 ± 0.8 in. measured using a linear voltage differential transducer (LVDT) (680 ± 20 mm), respectively. connected to the unloaded end of the strand. The AASHTO-Type II girders have overall lengths of 31 ft (9.4 m) with center-to-center spans of 29 ft (8.8 m). The girders were prestressed with eight 0.6 in. (15.2 mm) diameter Phase 3: Structural Performance of Full-Scale Grade 270 low-relaxation prestressing strands of six straight AASHTO-Type II Girders strands and two strands harped at double harping points The structural performance of full-scale AASHTO precast, located 4 ft 11 in. (1.5 m) from mid-span as shown in Figure 1. prestressed bridge girders constructed with selected SCC mix- The pretensioning jacking system was calibrated to ensure ac- tures was investigated to evaluate the applicability of current curate application of the force to each strand. design provisions (AASHTO and PCI) and to recommend ap- The four mixes were proportioned with Type III cement propriate modifications to the AASHTO LRFD Specifications. and 20% Class F fly ash and crushed aggregate with MSA of The aspects studied were constructability, temperature varia- 1 /2 in. (12.5 mm), as presented in Table 8. c 6" 6" 1'-0" 9'-7" 4'-11" 31'-0" total length 48" 6.5" 12" 2-0.6" strands AASHTO 36" Type II girder 6-0.6" 2" strands 3" Section at ends Section at midspan Figure 1. Details of precast pretensioned AASHTO-Type II girders.
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20 Table 8. Mixtures used for full-scale girders. Targeted 56-day Codification* Concrete compressive (w/cmbinder contentbinder typeS/AVMA) strength 8,000 psi 38-797-III20%FA (w/cm = 0.38, Type III cement + 20% (55 MPa) Class F fly ash) HPC 10,000 psi 33-793-III20%FA (w/cm = 0.33, Type III cement + 20% (69 MPa) Class F fly ash) 8,000 psi 38-742-III20%FA-S/A54 (w/cm = 0.38, Type III cement (55 MPa) + 20% Class F fly ash, S/A = 0.54) SCC 10,000 psi 32-843-III20%FA-S/A46-VMA (w/cm = 0.32, Type III (69 MPa) cement + 20% Class F fly ash, S/A = 0.46) * ½ in. (12.5 mm) crushed aggregate for all mixtures The testing program of the concrete used in the girders then moist cured at 100% RH and 73.4°F (23°C) until testing. is presented in Table 9. For each girder, a minimum of fifty At the time of prestress release, three steam-cured and three 4 × 8 in. (100 × 200 mm) cylinders and eighteen 3.9 × 3.9 × air-cured cylinders were tested to determine the compressive 15.7 in. (100 × 100 × 400 mm) beams were prepared. In total, strength. 28 cylinders and nine flexural beams were match cured with Four cylinders, two for each curing method, were used to the concrete girders. The rest of the cylinders and flexural determine the modulus of elasticity. The remaining steam- beam specimens were demolded after 18 hours of air curing, cured cylinders were stored near the girders and tested to Table 9. Concrete testing program for the girders. Number Size/volume SCC Test Test of samples Property of Comments behavior method age per specimen mixture Modified At arrival Yield stress, Tattersall Not 0.89 ft3 Rheology & after plastic viscosity MK III applicable (25 l) casting rheometer At arrival Slump flowa, Filling ASTM C & just Not 0.11 ft3 T-50 (upright ability 1611 after applicable (3.14 l) cone position) casting ASTM C Passing J-Ring At arrival 1621 Not 2.54 ft3 ability, & after filling L-box, See applicable (72 l) casting capacity caisson filling Attachment capacity D 7.9 × 23.6 in. See (200 × 600 mm) Surface Over Attachment 1 settlement 24 hours cylindrical D specimens 7.9 × 26 in. Column ASTM C (200 × 660 mm) 1 Stability segregation 1610 cylindrical specimens Visual stability ASTM C Not 0.11 ft3 (3.14 l) index 1621 applicable At arrival AASHTO Not 0.25 ft3 Stability of air & after T 152 applicable (7 l) casting Embedded 3 × 3 × 11.2 in. Autogenous Over 1 vibrating 2 (75 × 75 × 285 Visco- shrinkage month wire gages mm) prismb elastic properties 6 × 12 in. AASHTO Over 6 Drying shrinkage 3 (150 × 300 T 160 months mm) cylinder c a Slump for HPC mixtures b Sealed prisms after demolding at release time c Same curing regime used for release strength