Dr. Randy West, P.E. Director / Research Professor Update on the MnROAD-NCAT Cracking Group Experiments Dr. Randy West, P.E. Director / Research Professor Thank you Don for the invitation to speak to the OLLI. OK, so I’m sure that some of you are thinking “what a great way to get a week started off. Have some engineer come talk about asphalt. How exciting!”

we have no way of knowing if these materials help or hurt With the current volumetric mix design system… Recycled Shingles WMA additives Fractionated RAP Recycling agents we have no way of knowing if these materials help or hurt Aramid & Polyolefin fibers Recycled Tire Rubber

Balanced Mix Design Cracking Resistance Rutting Resistance

Validation of Performance Tests Researchers typically develop methods independently Most tests lack a regional or national validation effort with field pavements Most have unknown precision statistics Laboratory aging protocols are still being researched

MnROAD + NCAT Partnership Working together on national need research projects Validating cracking tests for balanced mix design Documenting the life cycle benefits of Pavement Preservation

Modes of Cracking Fatigue Thermal Top-Down Reflection Block Load Related Environment Related

Scope of Experiments MnROAD NCAT Test Track Low-temperature cracking Top-down cracking

Top-Down Cracking Sections on the NCAT Test Track Surface Layer 1.5” Intermediate Layer 2.25” Base Layer Granular base 6” Stiff track subgrade infinite Cracking Group sections 7 200-ft. sections each section instrumented HiMA mix

CG Performance through 1 cycle, 10 MESALs Section Description Rutting (mm) Δ IRI (in/mi.) Δ MTD (mm) Cracking (% of lane) N1 20% RAP (Control) 1.7 3 0.4 21.5 N2 Control w/ High Density 2.2 7 0.5 6.2 N5 Low AC, Low Density 1.2 5 5.0 N8 20% RAP 5% RAS 13 0.7 16.9 S5 35% RAP PG 58-28 1.5 1 S6 Control w HiMA 1.4 10 0.6 S13 AZ Rubber Mix 2.8 0.1

Progression of Cracking

Selected Top-Down (Intermediate Temp. Fracture) Cracking Tests Added early summer 2017 Energy Ratio SCB-LA IFIT OT-TX OT-NCAT IDEAL-CT We need to find a cracking test that we can count on to indicate performance. Actually, it may be different tests for different forms of cracking. But this webinar is not going to get into the pros and cons of the different tests. These tests are being conducted on both lab mix and plant mix samples that are aged and unaged. Also conducting cyclic fatigue (SVECD) with FlexPave analysis

Lab Mixed Lab Compacted Plant Mixed Lab Compacted Status of Lab Work Test Lab Mixed Lab Compacted Plant Mixed Lab Compacted 4 hrs. at Comp. Temp. 8 hrs. at 135°C Reheated Energy Ratio X IFIT SCB-Jc OT OT-NCAT Ideal CT 8 hrs at 135°C = “critically aged” which corresponds to 70,000 CDD

MnROAD Cracking Group Test Section Update

MnROAD Test Sections Test sections constructed August 2016 17 23 22 21 20 19 18 Cracking Group Cells 16-23 Test sections constructed August 2016

Asphalt Mixtures CELL NO BINDER GRADE ABR % RAS 16 64S-22 30-40 Yes 17 20-30 18 15-25 No 19 20 52S-34 25-35 21 58H-34 221 23 64E-342 10-20 All mixes are 12.5 mm NMAS All mixes are Ndes = 80 and target air voids = 4.0% except cell 19 which has Ndes = 100 and target air voids = 3.0% 1 Cell 22 limestone aggregate in mix 2 Highly modified asphalt binder

Cracking Modes and Testing Types of cracking investigated Low temperature Top-down or bottom-up fatigue possible PMLC testing Low temp: DCT-MN and IDT Creep Intermediate temp: IFIT, OT, BBF E*, TSR, Hamburg Critically-aged PMLC now in planned Samples provided to other research studies

Performance Tests Research is ongoing select best test(s) set mix aging protocol(s) establish criteria determine precision statistics Numerous agencies and contractors are testing the waters to understand how BMD will change mix designs