Diese Präsentation wurde erfolgreich gemeldet.
Wir verwenden Ihre LinkedIn Profilangaben und Informationen zu Ihren Aktivitäten, um Anzeigen zu personalisieren und Ihnen relevantere Inhalte anzuzeigen. Sie können Ihre Anzeigeneinstellungen jederzeit ändern.

Optimization of Pavement Concrete

107 Aufrufe

Veröffentlicht am

Jiong Hu

Veröffentlicht in: Business
  • Als Erste(r) kommentieren

  • Gehören Sie zu den Ersten, denen das gefällt!

Optimization of Pavement Concrete

  1. 1. 01/22/2019, 40th Annual NCPA Concrete Paving Workshop Dr. Jiong Hu, Department of Civil Engineering, University of Nebraska- Lincoln
  2. 2.  Nebraska Department of Transportation for the support of the research project  Lyman-Richey Corporation and Ash Grove Cement Company for donating materials for the research  Mr. Miras Mamirov (GRA) and Dr. Yong-Rak Kim (co-PI) 2
  3. 3. Introduction  Objectives  NDOT Historical data Particle Packing  Experimental (Combined Aggregate Void Content Test)  Theoretical (Modified Toufar Model) Experimental Program  Materials  Test Methods  Testing Matrix Phase-1 Study Phase-2 Study Proposed Mix Design Procedure Conclusions 3
  4. 4. Reduction of cement content  Durability  Cost Comparison of measured shrinkage over drying time 4 MeasuredShrinkage Drying Time Aggregates Optimized graded concrete Covnentional concrete Paste Cost comparison of concrete main ingredients 0 20 40 60 80 100 120 140 Aggregates Cement Water Cost($/ton)
  5. 5. 5 Aggregate gradation optimization Granular skeleton Equivalent volume Excess paste Paste to fill in voids among aggregate particles Aggregate particles
  6. 6. 0 5 10 15 20 25 30 35 40 45 1.5" 1" 3/4" 1/2" 3/8" No. 4 No. 8 No. 16 No. 30 No. 50 No. 100 No. 200 Percentretained(%) Sieve size Tarantula upper Tarantula lower Eastern (Columbus) 85SG-15L Eastern (Columbus) 85SG-15C Western (Sidney) 55SG-45CN Western (Sidney) 60SG-40CN Western (Sidney) 60SG-20CN-203/4" Western (Sidney) 70SG-30CN Central (Gothenburg) 7047B-30Roof Western (Sidney) 85F2A-15CN Western (Sidney) 60SG-20RG-201-3/8 70% Western sand and gravel-30% Martin Marietta ledge rock (2015) 70% Sand and gravel-30% ledge rock (Big springs, May, 2015) 70% Sand and gravel-30% ledge rock (Big springs, June, 2015) 70% Sand and gravel-30% ledge rock (West Sidney, July, 2015) 6Aggregate gradations used in Nebraska (Heyen et al. 2013)
  7. 7. 7 Experimental Combined void content test Rodding Jigging Shoveling Others Theoretical Empirical 0.45 power chart Shilstone 8-18 Tarantula Others Scientific Aim’s and Goff’s Model Modified Toufar Model Modified A&A model Others More accurate optimization
  8. 8. 8 a) #57 Limestone; b) Sand and Gravel a b Pozzolan Content, % 25 MgO, % 2.1 SO3, % 3.5 Loss on Ignition, % 1.5 Blaine Fineness, cm2/g 4200 Specific Gravity 2.95  Cement  IP cement is a blended hydraulic cement which is inter-ground with 25% class F fly ash  IP cement is designed to mitigate ASR, provide exceptional sulfate resistance and  Aggregates IP cement properties Aggregate gradation 0 10 20 30 40 50 60 70 80 90 100 %Passing Sieve Size (mm) #57 Limestone Sand&Gravel 1.5"1"3/4"1/2"3/8#4#8#10#16#30#50#100#200
  9. 9. 9 Vibration plus pressure method Combined aggregated void content test setup 𝐺 𝑠𝑏,𝑐𝑜𝑚𝑏𝑖𝑛𝑒𝑑 = 1 𝑃𝐶𝐴 𝐺 𝑠𝑏,𝐶𝐴 + 𝑃𝐹𝐴 𝐺 𝑠𝑏,𝐹𝐴 𝐵𝑢𝑙𝑘 𝐷𝑒𝑠𝑛𝑖𝑡𝑦 = 𝑀𝑎𝑠𝑠 𝑉𝑜𝑙𝑢𝑚𝑒 %𝑉𝑜𝑖𝑑 = 𝐺 𝑠𝑏,𝑐𝑜𝑚𝑏𝑖𝑛𝑒𝑑 × 𝑈𝑊 𝑤𝑎𝑡𝑒𝑟 − 𝐵𝑢𝑙𝑘 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝐺 𝑠𝑏,𝑐𝑜𝑚𝑏𝑖𝑛𝑒𝑑 × 𝑈𝑊 𝑤𝑎𝑡𝑒𝑟  Combined aggregate void content test – Modified ASTM C29 (Obla et al. 2007)  Compaction methods  Rodding, jigging, shoveling (ASTM C29)  Vibration plus pressure (De Larrard 1999)
  10. 10. Φ = 1 𝑉1 𝜑1 + 𝑉2 𝜑2 − 𝑦2 ∗ 1 𝜑2 − 1 ∗ 𝑘 𝑑 ∗ 𝑘 𝑠 Where, V1, V2 – fraction of fine and coarse particles Ф1, Ф2 – packing density of fine and coarse particles kd – characteristic diameter factor ks – statistical factor 10  Modified Toufar Method - discrete packing model (Goltermann 1997)  Input required: characteristic diameter and individual packing degree (ASTM C29)  Packing degree can be obtained by:
  11. 11.  Checks the response of concrete to vibration  Checks the ability of slip formed concrete to hold an edge Box test ranking scale Bottom edge and top edge slumping, Cook et al. (2016) Box test setup Cook et.al.(2016) defined “passing the box test” as if:  The side has less than 30% surface voids  Edge slumping is less than ¼ inches 11
  12. 12. 12 a b Surface voids form ImageJ Examples of Box test results with different edge holding abilities: a) 1-good; b) 2-average; c) 3-poor; d) 4-fail; e) 0- fail (excess paste) 0-3% 1 3-5% 2 5-15%3 15-100%4 Surface voids form Cook et al. (2016) EX- SX Edge Surface good1 average2 poor3 fail4 or 0
  13. 13. 13  Compressive strength (ASTM C39)  Modulus of rupture (ASTM C78)  Surface and bulk resistivity (AASHTO TP95)
  14. 14. 14 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Packingdegree SG/A ratio Vibration plus pressure Theoretical Experimental 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Packingdegree SG/A ratio Rodding Theoretical Experimental 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Packingdegree SG/A ratio Jigging Theoretical Experimental 0.55 0.60 0.65 0.70 0.75 0.80 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Packingdegree SG/A ratio Shoveling Theoretical Experimental 0 5 10 15 20 25 30 35 40 45 0 20 40 60 80 100 Voidcontent(%) Sand and gravel percentage (%) Rodding Jigging Shoveling Vibration plus pressure Combined aggregate void content test results Graphical comparison between experimental and theoretical packing degrees
  15. 15. 15 Mix concrete Conduct fresh concrete tests Did it pass the Box test? Put concrete back in to mixer Add Water reducer (WR) and remix for 3 minutes Cast specimens YesNo *Test procedure is adopted from Cook (2012) Conduct mechanical and durability tests at appropriate age  Experimental Phase-1  Obtain promising binary aggregate blends by mixing different blends with standard cement content (6 sacks = 564 pcy) • Blends selected: 70SG-30LS (reference), 60SG-40LS, 55SG- 45LS, 50SG-50LS  Experimental Phase-2  Start reducing cement content of reference and the promising blends at 0.5 sacks (47 pcy) step
  16. 16. 16 Mix ID w/c CF LS SG Water AEA VOblend% Pt% Pe% CS6SG70LS30 0.43 564 912 2060 243 0.125 19.79 31.88 14.91 CS6SG60LS40 0.43 564 1216 1766 243 0.125 19.48 31.88 15.24 CS6SG55LS45 0.43 564 1368 1619 243 0.125 19.21 31.88 15.52 CS6SG50LS50 0.43 564 1520 1472 243 0.125 20.53 31.88 14.11 Note: all ingredients are in lb/yd3, except for the chemical admixtures (WR and ARA), which are in fl oz/cwt Mix proportions
  17. 17. 17 Results
  18. 18. 18 Mix ID w/c CF LS SG Water AEA WR VOblend% Pt% Pe% CS5.5SG70LS3 0 0.45 517 942 2128 233 0.125 4 19.79 30.21 12.83 CS5.5SG55LS4 5 0.45 517 1413 1672 233 0.125 0 19.21 30.21 13.46 CS5SG70LS30 0.45 470 972 2196 212 0.125 20 19.79 28.02 10.09 CS5SG55LS45 0.45 470 1458 1725 212 0.125 4 19.21 28.02 10.74 CS4.5SG55LS4 5 0.45 423 1504 1779 190 0.125 24 19.21 25.75 7.93 Note: all ingredients are in lb/yd3, except for the chemical admixtures (WR and ARA), which are in fl oz/cwt Mix proportions
  19. 19. 19 4 fl oz/cwt of WR 1 adjustment Total 20 fl oz/cwt of WR 4 adjustments Reducing cement to 5.5 sacks Reducing cement to 5.0 sacks Reference blend 70SG-30LS
  20. 20. 20 4 fl oz/cwt of WR 1 adjustment Total 24 fl oz/cwt of WR 3 adjustments Reducing cement to 5.0 sacks Reducing cement to 4.5 sacks Reducing cement to 5.5 sacks Optimum blend 55SG-45LS
  21. 21. 21 0 1000 2000 3000 4000 5000 6000 7000 564 517 470 423 Compressivestrength(psi) Cement content (pcy) 70SG-30LS 55SG-45LS 0 100 200 300 400 500 600 700 800 900 564 517 470 423 ModulusofRupture(psi) Cement content (pcy) 70SG-30LS 55SG-45LS 0 2 4 6 8 10 12 14 564 517 470 423 Surfaceresistivity(kΩ*cm) Cement content (pcy) 70SG-30LS 55SG-45LS 0 2 4 6 8 10 12 14 564 517 470 423 Bulkresistivity(kΩ*cm) Cement content (pcy) 70SG-30LS 55SG-45LS Effect of cement content on a) compressive strength; b) modulus of rupture; c) surface resistivity; d) bulk resistivity
  22. 22. 22 Effect of excess paste on surface voids from the Box test Aggregate blend design •Obtain individual packing degrees using vibration plus pressure method. •Select optimum blend using Modified Toufar Model. Paste design •Design a concrete mixture with a minimum of approximately 10.5% of excess paste. Lab trial mix •Perform Box test to justify if the designed mixture has sufficient surface quality and edge holding ability. An appropriate amount of WR might be applied. Adjustment •Should the trial mix not passing the Box test, go back to “Paste Design” step and adjust the mix design to have an extra 1% of excess paste. •Conduct lab trial test on the adjusted mix until an acceptable mix is obtained 0 5 10 15 20 25 30 7.93 10.09 10.74 12.83 13.46 14.11 14.91 15.24 Surfacevoids(%) Excess Paste (%) %Surface voids (after) %Surface voids (before)
  23. 23. Performance evaluation  Drying shrinkage (ASTM C157)  Restrained shrinkage (ASTM C1581)  Freeze/Thaw resistance (ASTM C666)  Wet/Dry resistance (NDOT standard) 23
  24. 24.  The modified Toufar Model is an effective tool for pavement concrete mix design that incorporates the packing degree of aggregates, which counts for the gradation, as well as the shape and texture characteristics.  Cement content can be effectively reduced by up to 1.0 sack (94 lb/yd3) when the optimum gradation is used, without compromising the fresh properties, mechanical properties, and permeability.  A mix design procedure considering both the theoretical and experimental void contents and the minimum excess paste volume can be used to design concrete with optimum cement content. 24
  25. 25. 25

×