Region 3 Materials February 23, Jeremy Lucero, Region 3 Materials Engineer

Transcription

1 Region 3 Materials February 23, 2017 Jeremy Lucero, Region 3 Materials Engineer

2 Deserts & Mountains Interstate and Low Volume Roads Independence Pass at 12,096 I 70 near Mack at 4,447 Colorado River

3 Project Examples of the Good and Bad One Randomly Selected Project from the last few years and one project with a good lesson. A period of good paving and bad paving was identified for the random project. Here are values that I typically track: Dust to Asphalt Ratio (D/A) Asphalt Film Thickness Theoretical Surface Area Voids Between % Depending on Traffic and Relative Asphalt Content Asphalt Content Relative to Voids Target from Design VMA Relative to Asphalt Content from Design Quality Levels Based on Accuracy & Precision Compaction-Mat and Joint Density Asphalt Content Voids or Gradation Possibly VMA

4 Project Example of Good and Bad Project No. 1 Job Mix Formula values determined from the Contractor s Mix Design 5.7% AC 3.5% Voids 15.7% VMA Values that I track determined from the mix design 9.0% AFT 1.21 D/A The Bad The largest disincentive was from a period of low compaction resulting in a Quality Level of 53-Condition Red What went wrong?

5 Project No. 1 The Bad What went wrong-the Bad Production Results vs Job Mix Formula Targets 5.6% AC vs 5.7% 2.3% Voids vs 3.5% 14.2 VMA vs 15.7 Additional Values that I track 8.1% AFT (Barely acceptable according to other state agencies) vs 9.0% 1.28 D/A vs 1.21 Outcome Every value tracked was worse than the mix design values or targets What about the good? The largest incentive was from a period of precise and accurate asphalt contents resulting in good compaction-condition Green

6 Project No. 1 The Good What went right-the Good Production Results vs Mix Design Values and Targets 5.8% AC vs 5.7%, Above Optimal 3.1% Voids vs 3.5%, Closer to Optimal 14.0 VMA vs 15.7, Worse than the Bad Example Additional Values that I track 7.7% AFT (Not acceptable according to other state agencies) vs 9.0% 1.53 D/A vs 1.21 Outcome When AC was at or above optimal the Quality Levels were higher. Lower fines would result in lower D/A, more Film Thickness, and better Voids value. We strive for optimal AC values because the data shows that higher Quality Levels are achieved when optimal AC is achieved.

7 The Good and The Bad Some mixes could be good and bad. AMAZING Just depends how you make it. RESULTS

8 Project Example No. 2 of Good and Bad Project No. 2 Job Mix Formula values determined from the Contractor s Mix Design 5.7% AC 3.0% Voids 8.4% AFT Values that I track determined from the mix design 1.08 D/A 14.6 VMA The Bad The largest disincentive was from a period of poor gradation values early in the project resulting in a Quality Level of 56-Condition Red. Poor gradation values result in low voids and VMA. The Project appeared to be headed in the wrong direction. What went wrong?

9 Project No. 2 The Bad What went wrong-the Bad Communication When the project was going bad, we requested a sit down with the Contractor. No suggestions were made, but we expressed our concerns about the direction the project was headed. What about the good? The Contractor and the Project Team were willing to work together.

10 Project No. 2 The Good What went right-the Good Communication After the sit down with the Contractor, the Quality Levels consistently reached QLs of 100 and the disincentive turned into a significant incentive. The Great The final results of the project were all good. The Contractor and the Project Team thanked each other after the project for being able to turn what appeared to be a bad project into a good project.

11 Lessons Learned Takeaways Higher AC Values typically result in better compaction values Target Voids are more attainable when target ACs are achieved Target ACs typically result in higher Quality Levels Communication between Process Control (QC) and Quality Assurance (QA) is Key Communication and Teamwork between Contractor and Project Team is Paramount

12 Questions? The Good and The Bad

13 Quality Assurance Panel Presentation How to Ensure Quality and Incentive Pay on CDOT Projects RMACES February 23, 2017 Tim Webb P.E., Region 5 Materials Engineer

14 CDOT Region 5 Encompasses 15 Counties in SW Colorado Approximately 1,600 Centerline Lane Miles of Roadways Terrain High Mountains to Desert 13 Mountain Passes over 9500 in elevation Roadways Principal Arterial (56%) Minor Arterial (26%) Major Collector (18%)

15 Materials Mission Region 5 Materials goal is to ensure that the highest quality roadway system is designed and constructed in the most cost effective manner, and thus easily maintained. A critical part of achieving this goal is to encourage the Contractor s production and placement of high quality materials and workmanship. A natural effect of this goal is to assist the Contractor in his work to achieve the maximum benefit (incentive) of his effort to produce a high quality and long lasting project. We are committed to maintain the highest integrity in this process to include open communication, fairness, and consistency.

16 CDOT Design Requirements Project A Leveling (ST) PG 58 28: 3/8 Nominal Max Aggregate Air Voids minimum VMA Top Mat (SX) PG 58 34: 1/2 Nominal Max Aggregate Air Voids minimum VMA Project B Leveling (ST) PG 58 28: 3/8 Nominal Max Aggregate Air Voids minimum VMA Top Mat (SX) PG 58 28: 1/2 Nominal Max Aggregate Air Voids minimum VMA

17 Optimum Mix Design Submitted Project A Leveling (ST): 7.00% AC content (7.00%) 2.0% Air Voids (2.0%) 16.2 VMA ( ) 2.40% Agg Absorption Top Mat (SX): 6.00% AC content (6.00 %) 3.1 Air Voids (3.1 %) 14.7 VMA ( ) 2.40% Agg Absorption Project B Leveling (ST): 6.50% AC content (6.60%) 2.3% Air Voids (2.0%) 15.8 VMA ( ) 1.30% Agg Absorption Top Mat (SX): 5.60% AC content (5.70%) 3.4% Air Voids (3.1%) 14.6 VMA ( ) 1.30% Agg Absorption CDOT Form 43 targets shown in RED

18 Optimum Mix Design Submitted Project A Leveling (ST): 7.00% AC content (7.00%) 2.0% Air Voids (2.0%) 16.2 VMA ( ) 2.40% Agg Absorption Top Mat (SX): 6.00% AC content (6.00 %) 3.1 Air Voids (3.1 %) 14.7 VMA ( ) 2.40% Agg Absorption Project B Leveling (ST): 6.50% AC content (6.60%) 2.3% Air Voids (2.0%) 15.8 VMA ( ) 1.30% Agg Absorption Top Mat (SX): 5.60% AC content (5.70%) 3.4% Air Voids (3.1%) 14.6 VMA ( ) 1.30% Agg Absorption CDOT Form 43 targets shown in RED

19 ST Mix Design Gradation Submitted Project A Project B

20 ST Mix Production History Project A Production commences. Unable to produce desired Air Voids, request from Contractor to raise AC% from 7.00 to 7.40 with no change in gradation. Air Voids continue to vary production stopped; new mix required. Project B Production commences. Only one set of high AC% tests which put them in Red condition. Plant issue quickly resolved. ST mix leveling completed under one mix design with reasonable incentive.

21 Project A Revised gradation ST Mix Production History Project A Production ½ complete at this point New mix achieves target Air Voids but AC% demand is now 7.60% The high AC% required to achieve target Air Voids led to variability in production. This contributed to MQL float and a low final Pay Factor.

22 A B ST Mix Issues Mix Design: highly absorptive aggregates combined with a gradation curve that showed little variance from the maximum density line generated a mix where the lab did not reflect field production. First request to correct assumed need for more AC. This attempt raised the production AC average outside the new AC tolerance. Lastly, volumetric targets achieved with the 3 rd mix design having a finer gradation and a higher AC demand (7.60%). This mix was variable in production with AC% red condition MQL twice (out of spec range; once high and finishing low at completion). Mix Design: with a more reasonably absorptive aggregate and a gradation curve that shows a little more variance from the maximum density line this mix better reflected lab to field production. Short high AC red condition samples still produced Air Voids and VMA within tolerance ranges with these elements showing incentive; this mix not as sensitive to AC% variations.

23 ST Mix Achievements Both projects in the end achieved CDOT quality requirements Low Air Void placement (crack reflection resistance) Protective layer between old mat and new surface course Necessary multiple lift placement to achieve smoothness ST Mix Failings Project A had trouble controlling the mixes during production Gradation curve for these ST mixes on project A too tight and/or fine for consistent production control Project A high fine aggregate absorption combined with the gradation issues contributed to variability Contractor achieves less incentive/more disincentive even though in the end CDOT quality requirements are met

24 Optimum Mix Design Submitted Project A Leveling (ST): 7.00% AC content (7.00%) 2.0% Air Voids (2.0%) 16.2 VMA ( ) 2.40% Agg Absorption Top Mat (SX): 6.00% AC content (6.00 %) 3.1 Air Voids (3.1 %) 14.7 VMA ( ) 2.40% Agg Absorption Project B Leveling (ST): 6.50% AC content (6.60%) 2.3% Air Voids (2.0%) 15.8 VMA ( ) 1.30% Agg Absorption Top Mat (SX): 5.60% AC content (5.70%) 3.4% Air Voids (3.1%) 14.6 VMA ( ) 1.30% Agg Absorption CDOT Form 43 targets shown in RED

25 SX Mix Design Gradation Submitted Project A Project B

26 SX Mix Production History Project A Single mix design utilized to produce top mat from start to finish Mix Pay Factors above 1.0 for all elements Mat Density achieved maximum incentive allowed Jt. Density achieved near maximum incentive allowed Project B Single mix design utilized to produce top mat from start to finish Mix Pay Factors above 1.0 for all elements Mat Density achieved near maximum incentive allowed Jt. Density achieved maximum incentive allowed

27 SX Mix Achievements Both projects achieved CDOT quality requirements for SX top mat Consistent Air Void production and placement Mix properties contribute to superior Density construction for both mat and joint placement elements Consistent production contributed to excellent, controlled placement to achieve smoothness Incentives were earned to reflect adherence to CDOT quality requirements

28 Incentive/Disincentive Comparison Project A Leveling ST mix (15,287 ton): No Mat/Jt. Density paid Mix properties paid: $44,026 ( $2.88/ton) Top Mat SX mix (23,177 ton): Mat/Jt: $58,443 Mix properties paid: $24,606 ($1.06/ton) Total Paid: $39,023 Project B Leveling ST mix (20,105 ton): No Mat/Jt. Density paid Mix properties paid: $12,282 ($0.61/ton) Top Mat SX mix (34,267 ton): Mat/Jt: $36,623 Mix properties paid: $35,100 ($1.02/ton) Total Paid: $84,005

29 Projects A and B Overview Project A s highly absorptive fine aggregate and fine gradation issues contributed to that project s struggle to achieve consistent AC/Air Voids (volumetric control). Both projects responded to rectify problems with proposals to modify mix design ( A ) or control production red condition swings ( B ). SX mixes were then closely monitored by both projects for variations in lab to field production properties with success.

30 Summary Start with a well researched mix design Highly absorptive aggregate increases AC demand and may also contribute to variability in production Understand your aggregate source prior to design assumptions Project A was produced from an unfamiliar pit Project B was produced from a very familiar pit Control your materials during production; use your process control Communicate often Communicate regularly and timely with production issues Do not hesitate to present honest evaluations of variability Frequent communication allows for real time, beneficial feedback, target setting, and sampling/testing from CDOT Finally, to note: both projects were actually designed (mix) and constructed by the same Contractor!

31 Questions and Comments? This area could be used for related text, pull quotes, numbers or graphics. The size of the text (14 pt.) is smaller than the primary text at left. It should be white or another light color from brand palette or, the color of this sidebar should be another darkish color from the palette so that things in this area are readable. Readability is the most important guide for choosing the color of the background and text.

32 Quality Assurance Panel Presentation How to Ensure Quality and Incentive Pay on CDOT Projects RMACES June 24, 2015 Craig Wieden, Region 2 Materials Engineer

33 CDOT Region 2 Encompasses 14 Counties in SE Colorado Approximately 2,500 Centerline Lane Miles of Roadways Terrain Mountains to Eastern Plains High Elev. 11,539 Feet at Hoosier Pass Low Elev. 3,365 Feet Kansas Border Roadways Interstate Highways (125,000 AADT) Low volume rural roads (40 AADT) Air Temps from 110ºF to -50ºF

34 Contractors: Urban areas fixed asphalt plants Rural areas mobile plants Material Sources: Hard Rock Quarries Alluvial and River Deposits

35 CDOT HMA Acceptance Criteria Voids Acceptance AC Content Air Voids Voids in Mineral Aggregate Mat Density Joint Density Gradation Acceptance AC Content Gradation Mat Density Joint Density 15% 25% 45% 15% Gradation Acceptance Weighting Voids Acceptance Weighting 10% 30% 10% 35% 15%

36 Voids Acceptance Maximum PF

37 Mix Design Consistency/Uniformity of materials Process Control (Quality Control) for: Production Placement Plant Capabilities and Control How to Ensure Quality

38 Good Quality Example Mix Design and Materials 18% - ½ Rock 41% - Crusher Fines 10% - Clean Crusher Fines 11% - Natural Sand 19% - Fractionated RAP 1% - Hydrated Lime Production Targets set were: AC 5.4% Air Voids 3.2% VMA 14.6% Mix Design Fine Aggregate Angularity 46.4

39 Aggregates ½ Rock Crusher Fines Clean Crusher Fines Natural Sand RAP

40 Production Gradations

41 Good Quality AC Content and Volumetrics Total of around 27,000 tons of HMA produced AC content target was 5.4% Average AC (28 tests) was 5.47% AC Standard Deviation was 0.08% Air Voids Target was 3.2% Average Air Voids were 3.3% Air Voids SD was 0.5% VMA Target was 14.6 (14.7 after 1 st 3 Tests) Average VMA was 14.8 VMA SD was 0.3% What do these kind of numbers result in? AC content Quality Level of Air Voids Quality Level of VMA Quality Level of PF s for all three elements were Which is the maximum allowable PF for this quantity of HMA.

42 Poor Quality Example Initial Mix Design and Materials 20% - 9/16 Rock 49% - Crusher Fines 20% - Natural Sand #1 10% - Natural Sand #2 1% - Hydrated Lime Production Targets set were: AC 5.7% Air Voids 3.6% VMA 14.7% Mix Design Fine Aggregate Angularity 45.7

43 Aggregates 9/16 Rock Crusher Fines Natural Sand #1 Natural Sand #2

44 Production Gradations Production Targets AC 5.7% Air Voids 3.6% VMA 14.7% AT 1 AC 5.51% Air Voids 2.0 VMA 13.0 INFO 1 AC 5.38% Air Voids 1.6 VMA 12.7

45 Poor Quality Example Re-Design and Materials 20% - ½ Rock 44% - Crusher Fines 20% - Natural Sand #1 15% - Washed Sand 1% - Hydrated Lime Production Targets set were: AC 5.7% Air Voids 3.6% VMA 15.3% Mix Design Fine Aggregate Angularity 45.2

46 Production Gradations Production Targets AC 5.7% Air Voids 3.6% VMA 15.3% 1 st Rep AC 5.25% Air Voids 3.0 VMA st 10K AC 5.37% Air Voids 3.7 VMA nd 10K AC 5.71% Air Voids 3.6 VMA 15.1

47 AC Content and Volumetrics Total of around 15,000 tons of top mat HMA produced AC content target was 5.7% Average AC (16 tests) was 5.46% AC Standard Deviation was 0.18% Air Voids Target was 3.6% Average Air Voids were 3.2% Air Voids SD was 0.9% VMA Target was 15.3 (14.6 after 1 st 3 Tests) Average VMA was 14.4 VMA SD was 0.63% What do these kind of numbers result in? AC content Quality Level of 59 Air Voids Quality Level of 78.2 VMA Quality Level of 94.1 PF for AC content PF for Air Voids PF for VMA 1.042

48 Summary Start with a good mix design Use good materials angular and clean builds VMA Rounded improves workability, but tends to collapse VMA What might work for gradation acceptance may not work on volumetric acceptance Control your materials! Consistent and Uniform Know your production capabilities Baghouse rejection and metering Stockpile moisture influence on your plant Use your process control It s a contract requirement, but is beneficial if used correctly

49 Questions and Comments? This area could be used for related text, pull quotes, numbers or graphics. The size of the text (14 pt.) is smaller than the primary text at left. It should be white or another light color from brand palette or, the color of this sidebar should be another darkish color from the palette so that things in this area are readable. Readability is the most important guide for choosing the color of the background and text. Thank you 18