Lightweight Concrete for High Strength - Expanded Shale & Clay

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2.4 Analysis Results and Discussion Figures.2.1 and 2.2 present the composite girder maximum simple-span length versus the girder’s concrete compressive strength for AASHTO Type II through V sections and Bulb-Tee 54, 63 and 72 sections. Normal weight concrete (solid symbols) and lightweight concrete results are given. The unit weights lightweight are the “low” and “high” values to provide the range of results. Girder lengths using 8 ksi (55.2 MPa) HPLC could be extended by up to about 4 percent (7-ft. (2.13 m) for 140-ft. (42.7 m) girders) as shown in Figure 2.1. The most significant length increases resulted from the use of the lightest concrete unit weight. The increase in length for Type II and III sections was less than for Type IV and V sections implying the use of HPLC provided the most significant benefit for girders with lengths over approximately 105 feet (32 m). Figure 2.2 shows trends similar to those for Bulb-Tee sections. HSLWC girder maximum live load deflections resulting from HS 20-44 loading increased between 15 and 22 percent on average when compared to girders of normal weight concrete. The lighter concrete unit weights experienced the greatest deflections; however, deflections were at most 85 percent of the AASHTO maximum allowable L/800 requirement (L=span length) compared to 57 percent for normal weight. The collective results of GVW, maximum girder length, and section type are shown in Figure 2.3. Since it was seen that AASHTO Type II and III girders showed little benefit from HSLWC, they were not included in graph. Within Figure 2.3, there are three data points for each section listed. The three points correspond with the three strengths of concrete. In each case, the leftmost of the three points represents 8 ksi (55.2 MPa). The center point represents 10 ksi (69 MPa), and the rightmost point represents 12 ksi (88.2 MPa). The average unit weight given in Table 2.1 was used for the lightweight (L) sections while a constant 150 lb/ft 3 (unit weight was used for the normal weight (N) sections. The most important finding is that it was possible to reach the target span of 150-ft. (45.7 m) without exceeding the 150-kip (68,181 kg) GVW limit through the use of HSLWC. There are three HSLWC girders that satisfy the requirement: Modified BT-63 (12 ksi), BT-72 (10 ksi) and Modified BT-72 (8 ksi). 2-3
12500 12000 Concrete Strength, fc' (psi) 11500 11000 10500 10000 9500 9000 8500 8000 7500 60 70 80 90 100 110 120 130 140 150 160 Girder Length (feet) NWC Type V LWC Type V (Low) LWC Type V (High) NWC Type IV LWC Type IV (Low) LWC Type IV (High) NWC Type III LWC Type III (Low) LWC Type III (High) NWC Type II LWC Type II (Low) LWC Type II (High) Figure 2.1 Maximum girder length vs. concrete strength for AASHTO girders using normal weight concrete (NWC) and low to high density lightweight concrete (LWC). Concrete Strength, fc' (psi) 12500 12000 11500 11000 10500 10000 9500 9000 8500 8000 7500 105 115 125 135 145 155 Girder Length (feet) NWC BT-54 LWC BT-54 (Low) LWC BT-54 (High) NWC BT-63 LWC BT-63 (Low) LWC BT-63 (High) NWC BT-72 LWC BT-72 (Low) LWC BT-72 (High) Figure 2.2 Maximum girder length vs. concrete strength for Standard Bulb-Tee girders using normal weight concrete (NWC) and low to high density lightweight concrete (LWC). 2-4
Page 1 and 2: School of Civil and Environmental E
Page 3 and 4: ACKNOWLEDGMENTS The research presen
Page 5 and 6: A statistical evaluation based on f
Page 7 and 8: 5.6 - Transfer Length 5-13 5.7 - Gi
Page 9 and 10: Report ACI 318- 99 AASHTO Standard
Page 11 and 12: Chapter 1. Introduction 1.1 Purpose
Page 13 and 14: Long term properties including pret
Page 15: ottom flange. Prestressing strands
Page 19 and 20: Chapter 3. Mix Designs, Field Evalu
Page 21 and 22: Variation of coarse-to-fine aggrega
Page 23 and 24: 3.2.1 Compressive Strength Figure 3
Page 25 and 26: Table 3.5 Chloride Permeability --
Page 27 and 28: 12,000 11,500 11,000 Compressive St
Page 29 and 30: 1,400 1,300 1,200 1,100 Experimenta
Page 31 and 32: strength (10L made in the laborator
Page 33 and 34: The 50% and 90% of the 620-day cree
Page 35 and 36: 700 600 10,000-psi Measured Shams &
Page 37 and 38: a Creep Coefficient 3.0 2.5 2.0 1.5
Page 39 and 40: Chapter 5. Behavior of AASHTO Type
Page 41 and 42: Portion of Girder Damaged During Te
Page 43 and 44: 2” End Cover (Typ both ends) 4 Sp
Page 45 and 46: 5.3 Instrumentation The surface of
Page 47 and 48: Figure 5.7 Installation of stirrups
Page 49 and 50: Table 5.3 Girder concrete propertie
Page 51 and 52: 120 100 80 Stress (ksi) 60 40 20 0
Page 53 and 54: Table 5.5 -Transfer Length Results
Page 55 and 56: Figure 5.12 Typical flexural failur
Page 57 and 58: Since G2 girders had a higher concr
Page 59 and 60: V " pc cw− Pr ed = ft −Pr ed 1
Page 61 and 62: Test # Table 5.9 Predicted vs. Expe
Page 63 and 64: this research project, modification
Page 65 and 66: 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
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aggregate must be saturated by pres
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A.7.2 Strength Ceiling Harmon discu
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compared to lower strength specimen
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A.8.8 Deatherage, Burdette and Chew
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3. Concrete compressive strength at
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findings were comments that the AAS
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including strand diameter, embedmen
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l d = l t + l fb = f si 3 d b + 1.5
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l d = l t + l fb ⎛ = ⎜ ⎝ f d
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Table A.1 Summary of Development Le
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strand release, the strand attempts
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Appendix B. Creep and Shrinkage B.1
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Changes in moisture migration: the
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t′: age of concrete at loading (d
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s: slump (in) γ ψ ⎧ 0.30 −1.4
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t: age of concrete (days) t 0 : age
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where ε sh ∞ ⎧ 510 µε for st
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left girder-end. The dimension L wa
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6” 85” 50” Segment of girder
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146” 89” 96” 137” Stirrups
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were added in a specific sequence f
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C.2.3 Formwork Removal, Detensionin
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Figure C.19 Mostafa Prestressing St
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Figure C.22 Ms. Lyn Clements (GDOT)
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If significant strand end slip over
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CSS at Level of Bottom Strands (µ
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Appendix D. Prestress Losses in HPL
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E ps : elastic modulus of prestress
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D.2.2. AASHTO-LRFD Refined Estimate
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∆f log(24 ⋅t) ⎛ f ⎜ ⎞ 55
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P i : initial prestressing force af
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References AASHTO (1996), Standard
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ASTM C 618, Standard Specification
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Guide for Structural Lightweight Ag
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Martin, L. D., Scott, N. L., “Dev
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Shahawy, M. A., Batchelor, B., “S
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Lightweight Concrete for High Strength - Expanded Shale & Clay

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