CRACKING TESTS WORKSHOP

Transcription

1 NCHRP 9-57 Experimental Design for Field Validation of Laboratory Tests to Assess Cracking Resistance of Asphalt Mixtures CRACKING S WORKSHOP Sponsored by National Cooperative Highway Research Program Transportation Research Board of The National Academies and Texas A&M Transportation Institute Newport Beach, CA February 11 12, 2015

2 DCT Low temperature cracking and reflection cracking D = 6 in. T = 2 in. 2 holes D = 1 in. ND = 2.46 in. ASTM D7313 (Monotonic test) Fracture energy Little time 4 cuts and 2 holes Gluing 2 studs; mounting 1 clip gauge Good correlation with lowtemperature cracking validated at MnRoad Commercially available; Cost: $49, min. Quick and easy (pass/fail criteria) Notes 1. D = diameter; L = length; W = width; T = thickness; ND = notch depth 2. AV = air voids; Pb = percent binder Low (COV=10 15%) SENSITIVITY Asphalt binder, aggregate, RAP/RAS, and aging; insensitive to AV and P b Adopted by Minnesota and Wisconsin; being considered by Colorado, South Dakota, and Montana

3 SCB AT LOW TEMPERATURE Low temperature cracking D = 6 in. T = 1 in. ND = 0.6 in. AASHTO TP105 (Monotonic test) Fracture energy Medium time 4 cuts Gluing 3 studs; mounting 1 extensometer and 1 clip gauge Good correlation with lowtemperature cracking validated at MnRoad Commercially available; Cost: $52, min. Quick and easy (pass/fail criteria) Medium (COV=20%) SENSITIVITY Asphalt binder, aggregate, RAP/RAS, AV, and P b Being considered by Utah, South Dakota, Pennsylvania, and Montana

4 IDT FOR LOW TEMPERATURE CRACKING Low temperature cracking D = 6 in. T = in. AASTHO T322 Creep compliance and tensile strength Medium time 2 cuts Gluing 8 studs with a template; mounting 4 sets of extensometers 4 6 hours Longer time with cracking model to predict performance Notes 1. D = diameter; L = length; W = width; T = thickness; ND = notch depth 2. AV = air voids; Pb = percent binder Creep compliance and tensile strength inputs to TCMODEL; calibrated and validated through original SHRP and MEPDG Low (COV<11%) SENSITIVITY Asphalt binder, aggregate, RAP/RAS, aging Hydraulic test machines can be used and may cost more than $100,000 AASHTO T322 is required by AASHTOWare

5 TSRST/UTSST Low temperature cracking L = 10 in. W = 2 in. T = 2 in. (D = 2.25 in. L = 5.25 in.) AASHTO TP10/University of Nevada at Reno (Monotonic test) Fracture temperature (coefficient of thermal contraction from UTSST) Longer than medium time 4 cuts for long beam specimen; 2 cuts, 1 coring for cylinder specimen; gluing top and bottom platens Mounting 2 LVDTs Specimen 3 5 hours Data Data Short and easy (pass/fail criteria) Validated with test sections during SHRP program; MnRoad test results showed moderate correlation with field performance Low (COV= around 10%) SENSITIVITY Asphalt binder, aggregate, AV, P b, and aging Commercially available; Cost: $98,000 Being considered by Nevada

6 TEXAS OT Reflection cracking and bottom-up fatigue cracking L = 6 in. W = 3 in. T = 1.5 in. Tex-248-F (cyclic tests) No. of cycles (or fracture parameters: A and n) Medium time 4 cuts; gluing to two bottom plates None Good correlation with reflection cracking validated in Texas, California, and New Jersey; promising correlation with fatigue cracking validated with FHWA-ALF and NCAT test track Commercially available; Cost: $46, min. 3 hours Short and easy (pass/fail criteria) Notes 1. D = diameter; L = length; W = width; T = thickness; ND = notch depth 2. AV = air voids; Pb = percent binder Relatively high (COV=30 50%) SENSITIVITY Binder, aggregate, P b, RAP/RAS, aging, etc. Adopted by Texas and New Jersey; being considered by Montana, Nevada, Florida, and Ohio

7 BENDING BEAM FATIGUE Bottom-up fatigue cracking L = 15 in. W = 2.5 in. T = 2 in. AASHTO T321 (cyclic tests) No. of cycles (or fatigue equation) Medium time Large slab; 4 cuts Gluing 1 stud and mounting 1 LVDT Correlation with bottom-up fatigue cracking historically validated Frame (fixture) commercially available. Universal testing machine needed; could be > $100,000 Specimen 1 hour to days Data Data Short and easy (pass/fail criteria) Very high (COV>50%) SENSITIVITY Asphalt binder, aggregate, RAP/RAS, aging, etc. California special pavement design; being considered by Nevada and Georgia

8 SCB AT INTERMEDIATE TEMPERATURE Top-down fatigue cracking and reflection cracking D = 6 in. T = 2.25 in. ND = 1, 1.25, and 1.5 in. LTRC (Monotonic test) Critical energy release rate Very little time 5 cuts for 3 specimens None Good correlation to field cracking reported by LTRC Any hydraulic or pneumatic test system can be used; cost could be low 30 min. Quick and easy (pass/fail criteria) Notes 1. D = diameter; L = length; W = width; T = thickness; ND = notch depth 2. AV = air voids; Pb = percent binder Medium (COV=20%) SENSITIVITY Asphalt binder, aggregate, RAP/RAS Adopted by Louisiana and Wisconsin; being considered by Oklahoma and New Mexico

9 IDT FOR TOP-DOWN CRACKING Top-down cracking D = 6 in. T = in. University of Florida: M r test (optional), D t test, and tensile strength test (cyclic and monotonic tests) Energy ratio Medium time 2 cuts Gluing 8 studs with a template; mounting 4 sets of extensometers Validated with field cores in Florida and confirmed at NCAT test track Hydraulic test machines can be used and may cost more than $100, hours Short and easy (pass/fail criteria) Possibly low, similar to AASTHO T322 SENSITIVITY Insensitive to change in binder viscosity Being considered for adoption by Florida

10 S-VECD Bottom-up and top-down fatigue cracking S-VECD: D = 4 in. L = 5.1 in. (E*: D = 4 in. L = 6 in.) AASHTO TP107 (cyclic tests) Damage parameters (or predicted no. of cycles) Longer than medium time 2 cuts and 1 coring; gluing top and bottom platens with a jig Gluing 6 studs with a special glue jig; mounting 3 LVDTs 1 hour to 1 day (2 3 more days if E* test is considered) Easy if using ALPHA-fatigue software Longer time with pavement analysis programs (LVECD and VECD-FEP++) to predict pavement fatigue life Notes 1. D = diameter; L = length; W = width; T = thickness; ND = notch depth 2. AV = air voids; Pb = percent binder S-VECD used with more advanced models (LVECD and VECD-FEP++) to simulate pavement performance; validated with FHWA- ALF test lanes and verified in North Carolina Low in general, but need further evaluation SENSITIVITY Sensitive to binder content, RAP, aging, etc. as reported by Richard Kim s study Commercially available; Cost: $97,000 Being considered by Oklahoma, Georgia, Pennsylvania, and North Carolina

11 REPEATED DIRECT TENSION Bottom-up and top-down fatigue cracking D = 4 in. L = 6 in. Texas A&M University (cyclic tests) Paris law parameters, endurance limit, healing properties, and average crack size Longer than medium time 2 cuts and 1 coring; gluing top and bottom platens Gluing 6 LVDT holders; mounting 3 LVDTs 1 2 hours Easy with analysis software Measured properties with pavement analysis system to predict pavement fatigue life Correlations with bottom-up and top-down fatigue cracking being developed under several research projects; model and methods being validated with LTPP data Low in general, but need further evaluation SENSITIVITY Model coefficients functions of AV, P b, gradation; modulus, aging, etc. Universal test machine (MTS, AMPT) AMPT < $100,000. Unknown

12 A Member of The Texas A&M University System Saving Lives, Time and Resources