Project NEON Concrete Paving Mixture: Innovations and Challenges

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1 Project NEON Concrete Paving Mixture: Innovations and Challenges Thomas Van Dam, Ph.D., P.E., FACI Principal Thursday, November 29, 2018

2 Background Project NEON is using concrete for all interstatetype mainline pavements Typical section is 12 inches PCCP on 3 inches of HMA on 6 inches aggregate base Surfaced with 1 inch rubberized asphalt overlay NVDOT was the pavement designer A number of ATC were submitted Today the focus is on reducing the total cementitious content of the concrete paving mixture

3 NVDOT s 2014 Standard Specifications for PCCP Total cementitious content between 611 and 705 lbs/yd 3 Requires meeting a combined aggregate grading Minimum 28-day flexural strength of 650 psi for mix design acceptance Minimum flexural strength of 550 psi and 10 days for opening Minimum 28-day compressive strength of 4,000 psi for acceptance during construction

4 ATC: Optimized Concrete Paving Mixture Proposed concrete mixture with reduced cementitious content Improved workability Comparable compressive and flexural strength Reduced drying shrinkage Enhanced durability Reduced economic and environmental costs

5 ATC: Optimized Concrete Paving Mixture Rationalization Similar mixtures have been used successfully by a number of states including Texas, Montana, Washington, Oklahoma, Missouri, Wisconsin, Indiana, Kansas, Iowa, and Minnesota Estimated cost savings $350k to $500k NVDOT accepted the ATC with the stipulation that the test strip goes well This is a BIG DEAL

6 Proposed Mixture Based on P-501 paving concrete used at McCarran International Airport 500 lbs/yd 3 total cementitious 400 lbs/yd 3 Type V cement 100 lbs/yd 3 Class F fly ash Four aggregate blend, all from the same source No. 4, No. 67, No, 8, and washed concrete sand All 100% crushed limestone

7 Proposed Mixture Flexural Strength

8 Test Strip (September 29, 2017) Not an overwhelming success Overall concept was demonstrated Issues with concrete consistency observed Mixture varied from wet to very dry Edge crumbling Closing the surface was difficult

9 Test Strip Mixture: AE535FA Source of Weight Specific Volume Material Material (lbs/cy) Gravity (ft³) Coarse I (No. 4) Sloan Coarse II (No. 67) Sloan Coarse III (No. 8) Sloan Fine I (Man.) Sloan Cement Cemex Fly Ash Navajo Water Air 1.30% 0.35 Total 4255lbs/cy 26.99cf 157.7lbs/cf w/cm: 0.42 Fly Ash: 20% Paste Vol.: 23% Fine Sand: 20.16% Note: Mix design tables and Tarantula Curve outputs are from a spreadsheet provided by Tyler Ley

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19 Post Test Strip Actions Had a very good meeting following the placement of the test strip Agreed to tighten up mixture consistency Problem discovered and corrected at plant Reconsider aggregate grading Tarantula curve Concerns expressed about the manufactured fine aggregate Coarse grading 100% crushed limestone

20 Tarantula Curve From Tyler Ley

21 Percentage Passing(%) Aggregate Gradations 100% 90% 80% 70% 60% 50% 40% Coarse I 30% Coarse II Coarse III 20% Fine I 10% #200#100#50 #30 #16 #8 #4 3/8" 1/2" 3/4" 1" Fine II 0% 1.5" Sieve Number

22 Test Strip Mixture: AE535FA

23 Revamped Mixture: AE532FA Eliminated No. 8 Re-proportioned to meet Tarantula curve Bumped up entrained air to 3% bulk up paste and improve workability Second test strip reportedly went well

24 Revamped Mixture: AE532FA Source of Weight Specific Volume Material Material (lbs/cy) Gravity (ft³) Coarse I (No. 4) Sloan Coarse II (No. 67) Sloan Coarse III (No. 8) Sloan Fine I Sloan Cement Cemex Fly Ash Navajo Water Air 3.00% 0.81 Total 4174lbs/cy 26.99cf 154.7lbs/cf w/cm: 0.42 Fly Ash: 20% Paste Vol.: 23% Fine Sand: 23.45%

25 % Retained Revamped Mixture: AE532FA 25% 20% 15% 10% 5% 0% #200 #100 #50 #30 #16 #8 #4 3/8" 1/2" 3/4" 1" 1.5" Sieve No.

26 Construction Mainline paving initiated in January 2018 and continued into July 2018 using AE532FA exclusively All quality tests were reportedly met Everyone seemed happy

27 May 2018 Construction From Paul Brich, Kiewit

28 28-Day Average Flexural Strength (psi) 28-Day Flexural Strengths Day Average Flexural Strength AE /22/17 11/11/17 12/31/17 02/19/18 04/10/18 05/30/18 07/19/18 09/07/18 10/27/18 Date Placed

29 28-Day Average Compressive Strength (psi) 28-Day Compressive Strength Day Average Compressive Strength /22/17 11/11/17 12/31/17 02/19/18 04/10/18 05/30/18 07/19/18 09/07/18 10/27/18 Date Placed

30 Then Crow Gets Served

31 New Mix: AE703FA I got a call from NVDOT in September that Kiewit switched to a new mixture in mid-july for new G&Z S850 paver Two issues were affecting AE532FA Workability issues became more common in summer Edge crumbling and finishing issues Lower than desired early opening strength New mix (actually an old mix from 2016) with 611 lbs/yd 3 total cementitious (25% Class F FA) in accordance with NDOT s 2014 Standard Specifications Grading meets Tarantula Curve and kisses the edge of the NVDOT grading at the coarser sieves

32 New Mixture: AE703FA Source of Weight Specific Volume Material Material (lbs/cy) Gravity (ft³) Coarse I (No. 4) Sloan Coarse II (No. 67) Sloan Coarse III (No. 8) Sloan Fine I Sloan Cement Cemex Fly Ash Navajo Water Air 2.5% 0.68 Total 4098lbs/cy 26.97cf 151.2lbs/cf w/cm: 0.43 Fly Ash: 25% Paste Vol.: 28% Fine Sand: 21.11%

33 % Retained New Mixture: AE703FA 25% 20% 15% 10% 5% 0% #200 #100 #50 #30 #16 #8 #4 3/8" 1/2" 3/4" 1" 1.5" Sieve No.

34 From Paul Brich, Kiewit

35 28-Day Average Flexural Strength (psi) 28-Day Flexural Strength Day Average Flexural Strength AE532 AE703FA 0 06/14/17 08/03/17 09/22/17 11/11/17 12/31/17 02/19/18 04/10/18 05/30/18 07/19/18 09/07/18 10/27/18 Date Placed

36 10-Day Average Flexural Strength (psi) 10-Day Flexural Strength Day Average Flexural Strength AE532 AE703FA /14/17 08/03/17 09/22/17 11/11/17 12/31/17 02/19/18 04/10/18 05/30/18 07/19/18 09/07/18 10/27/18 Date Placed

37 3-Day Average Flexural Strength (psi) 3-Day Flexural Strength Day Average Flexural Strength AE532 AE703FA 0 06/14/17 08/03/17 09/22/17 11/11/17 12/31/17 02/19/18 04/10/18 05/30/18 07/19/18 09/07/18 10/27/18 Date Placed

38 28-Day Average Compressive Strength (psi) 28-Day Compressive Strength Day Average Compressive Strength AE532FA AE703FA 0 09/22/17 11/11/17 12/31/17 02/19/18 04/10/18 05/30/18 07/19/18 09/07/18 10/27/18 Date Placed

39 Volumetric Comparison Source of Volume (cft) Material Material AE535 AE532 AE703 Coarse I (No. 4) Sloan Coarse II (No. 67) Sloan Coarse III (No. 8) Sloan Fine I (Man.) Sloan Aggregate Cement Cemex Fly Ash Navajo Water Paste Air

40 Lessons Learned The Tarantula curve is an excellent tool, but it is just one tool Based concrete made with natural sands Gradations did not meet fine sand recommendations Consensus is that for this aggregate source, not enough paste was available at 500 lbs/yd 3 and a w/cm of 0.42 Coarse, manufactured sand needs more paste It is believed an additional 30 to 50 lbs/yd 3 binder was needed A finer natural sand with more rounded particles would have helped

41 Additional Thoughts (After Digesting Crow) There was a learning curve with the new G&Z S850 paver A dedicated concrete plant would have been helpful Issues with maintaining stockpile moisture More laboratory work would have been revealing Use Box Test or VKelley during mixture design (AASHTO PP-84) Get additional mixtures approved for changing conditions For pavements, higher strength is not necessarily good Information is emerging that design methods give too much credit to flexural strength Higher strength/stiffness can relate to brittleness

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43 QUESTIONS?

44 Thomas Van Dam, Ph.D., P.E., FACI Principal