Lightweight Concrete for High Strength - Expanded Shale & Clay

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cementitious materials, and the G2 series girders had 10 percent. Leming (1988), Vaysburg (1996), and Yeginobali et al. (1998) have stated that the addition of silica fume will significantly improve the tensile strength and bond of lightweight concrete to prestressing strand. The results of the present research confirm this observation. C-19
Appendix D. Prestress Losses in HPLC D.1 General Prestress losses in special concretes such as structural lightweight concrete (SLC), high performance concrete (HPC), and high performance lightweight concrete (HPLC) follow the same principles and are affected by the same factors that affect normal weight normal strength concrete (NWNSC), but they are influenced by the particular properties of each. Prestress losses in HPC: HPC usually has higher modulus of elasticity, a lower creep and a similar or lower shrinkage than a NSC. Based on that, it is expected to obtain fewer losses due to elastic shortening, fewer losses due to creep losses, similar or fewer losses due to shrinkage, and more losses due to steel relaxation. The expected increase in steel relaxation losses is a consequence of a higher stress level in the prestressing steel due to a decrease on concrete losses. Total losses are expected to be less than NSC. According Roller et al. (1995), measured longterm prestress losses in HPC prestressed girder were approximately 50% less than the expected value. Prestress losses in SLC: Properties of SLC may vary in a wide range, so the prestress losses may also widely vary. In general SLC presents a lower modulus of elasticity than a NWC of the same strength. It also has a higher ultimate creep and ultimate shrinkage than the NWC counterparts. Therefore, elastic shortening, and final creep and shrinkage losses are expected to be greater in SLC. Steel relaxation losses, however, are going to decrease due to the increase in the others. ACI-213 (1999) concluded that combined loss of prestress in a SLC member is about 110 to 115% of the total losses for NWC when both are cured normally. If they are steam-cured, prestress losses in SLC are expected to be 124% of the losses in NWC. PCI (1998) gave a range for total prestress losses of “sand-lightweight” members of 30,000 to 55,000 psi which is about 15% higher than the range given for NWC. Prestress losses in HPLC: To the authors’ knowledge, there is no previous research on prestress losses of HPLC; however, from the material properties some conclusions can be drawn. Elastic shortening losses are expected to be similar or less than NWNSC but more than HPC. Creep and shrinkage losses would be similar to the one of HPC. Steel relaxation losses would tend to be higher than losses in NWNSC because the previous losses are lower. D-1
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School of Civil and Environmental E
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ACKNOWLEDGMENTS The research presen
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A statistical evaluation based on f
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5.6 - Transfer Length 5-13 5.7 - Gi
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Report ACI 318- 99 AASHTO Standard
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Chapter 1. Introduction 1.1 Purpose
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Long term properties including pret
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ottom flange. Prestressing strands
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12500 12000 Concrete Strength, fc'
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Chapter 3. Mix Designs, Field Evalu
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Variation of coarse-to-fine aggrega
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3.2.1 Compressive Strength Figure 3
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Table 3.5 Chloride Permeability --
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12,000 11,500 11,000 Compressive St
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1,400 1,300 1,200 1,100 Experimenta
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strength (10L made in the laborator
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The 50% and 90% of the 620-day cree
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700 600 10,000-psi Measured Shams &
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a Creep Coefficient 3.0 2.5 2.0 1.5
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Chapter 5. Behavior of AASHTO Type
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Portion of Girder Damaged During Te
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2” End Cover (Typ both ends) 4 Sp
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5.3 Instrumentation The surface of
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Figure 5.7 Installation of stirrups
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Table 5.3 Girder concrete propertie
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120 100 80 Stress (ksi) 60 40 20 0
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Table 5.5 -Transfer Length Results
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Figure 5.12 Typical flexural failur
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Since G2 girders had a higher concr
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V " pc cw− Pr ed = ft −Pr ed 1
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Test # Table 5.9 Predicted vs. Expe
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this research project, modification
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Chapter 6. Prestress Losses in HPLC
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losses in the 10,000-psi girders to
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Microstrains (in/inx10 -6 ) 0 500 1
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6.3 Conclusions Regarding Prestress
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7.3 Transfer Length An evaluation o
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Shrinkage after 620 days of drying
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More research is required to examin
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Appendix A. Background A.1 Introduc
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Raithby and Lydon described the use
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are normally recognized as being on
Page 85 and 86: aggregate must be saturated by pres
Page 87 and 88: A.7.2 Strength Ceiling Harmon discu
Page 89 and 90: compared to lower strength specimen
Page 91 and 92: A.8.8 Deatherage, Burdette and Chew
Page 93 and 94: 3. Concrete compressive strength at
Page 95 and 96: findings were comments that the AAS
Page 97 and 98: including strand diameter, embedmen
Page 99 and 100: l d = l t + l fb = f si 3 d b + 1.5
Page 101 and 102: l d = l t + l fb ⎛ = ⎜ ⎝ f d
Page 103 and 104: Table A.1 Summary of Development Le
Page 105 and 106: strand release, the strand attempts
Page 107 and 108: Appendix B. Creep and Shrinkage B.1
Page 109 and 110: Changes in moisture migration: the
Page 111 and 112: t′: age of concrete at loading (d
Page 113 and 114: s: slump (in) γ ψ ⎧ 0.30 −1.4
Page 115 and 116: t: age of concrete (days) t 0 : age
Page 117 and 118: where ε sh ∞ ⎧ 510 µε for st
Page 119 and 120: left girder-end. The dimension L wa
Page 121 and 122: 6” 85” 50” Segment of girder
Page 123 and 124: 146” 89” 96” 137” Stirrups
Page 125 and 126: were added in a specific sequence f
Page 127 and 128: C.2.3 Formwork Removal, Detensionin
Page 129 and 130: Figure C.19 Mostafa Prestressing St
Page 131 and 132: Figure C.22 Ms. Lyn Clements (GDOT)
Page 133 and 134: If significant strand end slip over
Page 135: CSS at Level of Bottom Strands (µ
Page 139 and 140: E ps : elastic modulus of prestress
Page 141 and 142: D.2.2. AASHTO-LRFD Refined Estimate
Page 143 and 144: ∆f log(24 ⋅t) ⎛ f ⎜ ⎞ 55
Page 145 and 146: P i : initial prestressing force af
Page 147 and 148: References AASHTO (1996), Standard
Page 149 and 150: ASTM C 618, Standard Specification
Page 151 and 152: Guide for Structural Lightweight Ag
Page 153 and 154: Martin, L. D., Scott, N. L., “Dev
Page 155: Shahawy, M. A., Batchelor, B., “S
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Lightweight Concrete for High Strength - Expanded Shale & Clay

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