LTPP Lessons Learned: National Experiment

1. LTPP Lessons Learned: National Experiment July 17, 2013 Abilene, KS Jack Springer, P.E.—FHWA Gabe Cimini, Database Manager - NCRO

2. Lessons Learned Overview • LTPP Program Benefits and Return on Investment • Construction Effects on PCC Pavement Performance • Specific SPS-2 Lessons Learned • Pavement Performance • Pavement Design • Materials Testing • Data Collection • Future Benefits

3. LTPP Benefits The LTPP program has generated a wide range of benefits all across the pavement engineering and performance spectrum.

4. Return on Investment LTPP by the Numbers The numerous innovations that have directly resulted from the LTPP program include procedures, tools, manuals, and research findings that have been implemented across the United States and abroad.

5. Return on Investment Cost Savings LTPP has already realized over $2 Billion in savings, with the potential for even greater future savings.

6. Construction Effects on PCC Performance Note: X denotes no effect; ranking of 1-5 indicates best-worst performance

7. SPS-2 Lessons Learned—Pavement Performance • Standardizing AVC and WIM data storage formats (Card 4 and Card 7, respectively). • The initial IRI of SPS-2 sections after placement ranged from 0.76 to 2.19 m/km with a mean of 1.30 m/km. • Increased roughness, faulting and transverse cracking are more prevalent in wet climates. • Pavements located in areas of higher annual freeze-thaw cycles experience more spalling.

8. SPS-2 Lessons Learned—Pavement Design • Widened slab sections show less faulting than conventional width slabs. • Sections with aggregate base show the highest joint faulting level. Sections with LCB and PATB have the lowest joint faulting. • Thinner (203 mm) slabs show more transverse cracks than thicker slabs. Sections with a thinner slab and a widened slab show the highest level of transverse cracking.

9. SPS-2 Lessons Learned—Pavement Design (cont.) • JPCP constructed on PATB were smoother than sections constructed on LCB or untreated aggregate base. • Sections with PATB show the lowest total longitudinal cracking levels, while the sections with LCB show the highest longitudinal cracking. • Sections with PATB show the lowest percentage of slabs cracked transversely, while the sections with an LCB show the highest transverse cracking.

10. SPS-2 Lessons Learned—Pavement Design (cont.) • In general, LCB provided the worst performance and PATB over DGAB provided the best performance. • Longitudinal cracking was influenced by base type and slab thickness. • Widened lanes contributed to lower transverse joint faulting.

11. SPS-2 Lessons Learned—Pavement Design (cont.) • Thicker slabs were found to have more initial roughness as compared to thinner slabs. • The presence of drainage was the driving factor of change in roughness with time. Sections with drainage showed a slower increase in roughness than those without drainage. • 900 PSI sections typically show map cracking and 550 PSI sections typically show polished aggregate. • 14’ lane = 1” of thickness.

12. SPS-2 Lessons Learned—Pavement Design (cont.) Rigid Pavement Design

13. SPS-2 Lessons Learned—Materials Testing • JPCP constructed on coarse-grained soil were smoother (lower initial IRI) than those constructed on fine-grained soils. • PCC slabs placed on LCB displayed the largest amounts of curling and slabs placed on ATB displayed the smallest amounts of curling. • Concrete performed the worst with a lean concrete base (LCB) and the best with an asphalt treated base (ATB).

14. SPS-2 Lessons Learned—Materials Testing (cont.) • Six inches of LCB has approximately the same stiffness as 8 inches of ATB, both of which are less stiff than 8 inches of dense graded aggregate base (DGAB). • Creating the Materials Reference Library—which allows researchers to obtain and test materials used in constructing specific LTPP sections.

15. SPS-2 Lessons Learned—Materials Testing (cont.) • Collecting periodic non-destructive testing measurements to allow the backcalculation of in-situ moduli. • Developing standardized laboratory and field testing protocols. • Providing materials data for calibrating M-E PDG damage functions and performing M-E PDG pavement designs.

16. SPS-2 Lessons Learned—Data Collection • The IRI trend over time depends heavily on the initial IRI, the traffic loadings, and the extent of joint faulting. • Loads below design table ($2 million) • Standardizing data collection and quality control practices • Pavement distress • Automated profile • FWD

17. SPS-2 Lessons Learned—Data Collection • Indiana Department of Transportation found that an FWD that was only 1 mil out of calibration resulted in additional construction and maintenance costs of $17,000 per mile.

18. Future Benefits • Looking forward, there are many potential benefits LTPP can provide. A partial listing includes: • Increasing service lives for new and rehabilitated pavements, • Comparison of new vs. existing material performance “…We see the LTPP database serving into the indefinite future as a key component of the agency’s pavement research activities, and those activities will benefit substantially from the many LTPP data collection and analysis activities in FY 2010 -FY 2015 that are mentioned in the FHWA document.” Victor Mendez, Chairman Twenty-third letter report of the Transportation Research Board Long-Term Pavement Performance Committee

19. Future Benefits (continued) • Effects of specific design features • SHRP 2 support • Determining the impact of environment on performance • Baseline data sets for agencies to evaluate performance • Year-to-year checks against agency pavement management system/pavement condition index data “LTPP is a major contributor toward assuring that we will have good pavements into the 21st Century.” Charlie Churilla, “An Investment in the Future” Roads & Bridges, August 2001

20. Future Benefits (continued) • MEPDG local calibration and model refinement • Top-down vs. bottom-up cracking • Improved rutting prediction • Improved curing procedures to reduce built-in temperature gradients • Next design procedure (and state-specific design procedures) • Optimizing treatment selection • Constructing new sections to expand inference set • Calibration of new field data equipment • Refining concrete coefficient of thermal expansion (CTE) test protocol

21. Thank You More products and information at: http://ltpp-products.com For more information: www.fhwa.dot.gov/research/tfhrc/infrastructure/ pavement/ltpp