Comparing the Volumetric and Mechanical Properties of Laboratory and Field Specimens of Asphalt Concrete (2016)

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39 5.1 Individual Mixture Analyses The following sections present analyses of the data measured on the individual mixtures described in Chapter 4. Details of the analyses for the mixtures are presented in Appendix C. In the tables in the following subsections, crossed and shaded cells indicate significant difference; blank cells indicate that there is no statistical difference. The following abbreviations are used throughout the tables: LL: lab-mixed–lab-compacted, PL: plant-mixed–lab-compacted, PLR: plant-mixed–lab- compacted (reheated); PF: plant-mixed–field-compacted. 5.1.1 Summary of Mixture 1WI Analysis Tables 5-1 and 5-2 summarize the statistical comparisons conducted for Mixture 1WI. Statistically significant compari- sons are indicated with a crossed and highlighted cell. Results presented in the tables indicate that differences appear to be interrelated among the volumetric properties, which may be expected, because these properties depend on one another. On the other hand, differences in mechanical properties appear to be mainly influenced by the compaction effort and procedure, because the main differences were found between laboratory- compacted and field-compacted specimens. 5.1.2 Summary of Mixture 3MN Analysis Tables 5-3 and 5-4 summarize the statistical comparisons conducted for Mixture 3MN. Statistically significant com- parisons are indicated with a crossed and highlighted cell. Results presented in the tables indicate that differences occur throughout the volumetric and mechanical evaluation. The recycled asphalt pavement (RAP) provided for design (LL) specimens may have been different from the RAP used dur- ing production (PL and PF). This would explain the differ- ences observed between LL and PL specimens. Differences in mechanical properties appear to be mainly influenced by the compaction effort and process, because the main differ- ences were found between laboratory-compacted and field- compacted specimens. 5.1.3 Summary of Mixture 5WI Analysis Tables 5-5 and 5-6 summarize the statistical comparisons conducted for Mixture 5WI. Results presented in Table 5-5 indicate that the LL specimens were different from the plant- produced specimens for most volumetric properties. The main reason for these differences is possibly the low air voids of the LL specimens and a slight increase in fine contents. On the other hand, differences in mechanical properties appear to be mainly influenced by the compaction effort for laboratory- compacted and field-compacted specimens. In addition, differences between LL and PL specimens may be attributed to asphalt oxidation during the production process, differ- ences in air voids content (AV for LL = 7.9% vs. PL = 7.1% vs. PLR = 7.3%), or both. 5.1.4 Summary of Mixture 5LA90 Analysis Tables 5-7 and 5-8 summarize the statistical comparisons conducted for Mixture 5LA90. Results presented in Table 5-7 indicate that the LL specimens were different from the plant- produced specimens in most volumetric properties. The main reason for these differences is possibly the low air voids of the LL specimens and a slight increase in fines and asphalt binder contents. On the other hand, differences in mechanical properties appear to be mainly influenced by the compaction effort for comparisons of PL and PF specimens. In addition, differences between PL and PLR specimens may be attrib- uted to asphalt aging during time delay in specimen fabrica- tion, a large difference in asphalt content (AC for PL = 4.3% vs. PLR = 4.0%), or both. Given previous findings that reheat- ing had no effect, the difference appears more likely due to AC. C H A P T E R 5 Results and Discussion (text continues on page 46)

40 Table 5-1. Summary of the statistical comparisons (volumetrics)— Mixture 1WI. Property Comparison LL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR Air Voids NA VMA VFA Gmm AC Gsb Property Sieve Comparison LL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR Aggregate Percent Passing Sieve 12.5 mm 4.75 mm 0.600 mm 0.075 mm (a) (b) Table 5-2. Summary of the statistical comparisons (mechanical)— Mixture 1WI. (a) Property Passes ComparisonLL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR LWT Rut Depth 1,000 5,000 10,000 20,000

41 Property Comparison LL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR IDT Dynamic Modulus -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 10°C, 10Hz 10°C, 5Hz 10°C, 1Hz 10°C, 0.5Hz 10°C, 0.1Hz 35°C, 10Hz 35°C, 5Hz 35°C, 1Hz 35°C, 0.5Hz 35°C, 0.1Hz Temperature, Frequency (c) (b) Property Temperature, Frequency Comparison LL-PL LL-PLR PL-PLR Axial Dynamic Modulus -10°C, 25Hz -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 4°C, 25Hz 4°C, 10Hz 4°C, 5Hz 4°C, 1Hz 4°C, 0.5Hz 4°C, 0.1Hz 25°C, 25Hz 25°C, 10Hz 25°C, 5Hz 25°C, 1Hz 25°C, 0.5Hz 25°C, 0.1Hz 38°C, 25Hz 38°C, 10Hz 38°C, 5Hz 38°C, 1Hz 38°C, 0.5Hz 38°C, 0.1Hz 54°C, 25Hz 54°C, 10Hz 54°C, 5Hz 54°C, 1Hz 54°C, 0.5Hz 54°C, 0.1Hz Table 5-2. (Continued).

42 (a) Property Passes ComparisonLL-PLR LL-PF PLR-PF LWT Rut Depth 1,000 5,000 10,000 20,000 (b) Property Temperature, Frequency Comparison LL-PLR Axial Dynamic Modulus -10°C, 25Hz -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 4°C, 25Hz 4°C, 10Hz 4°C, 5Hz 4°C, 1Hz 4°C, 0.5Hz 4°C, 0.1Hz 25°C, 25Hz 25°C, 10Hz 25°C, 5Hz 25°C, 1Hz 25°C, 0.5Hz 25°C, 0.1Hz 38°C, 25Hz 38°C, 10Hz 38°C, 5Hz 38°C, 1Hz 38°C, 0.5Hz 38°C, 0.1Hz 54°C, 25Hz 54°C, 10Hz 54°C, 5Hz 54°C, 1Hz 54°C, 0.5Hz 54°C, 0.1Hz (c) Property Temperature, Frequency Comparison LL-PLR LL-PF PLR-PF IDT Dynamic Modulus -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz -10°C, 0.01Hz 10°C, 10Hz 10°C, 5Hz 10°C, 1Hz 10°C, 0.5Hz 10°C, 0.1Hz 10°C, 0.01Hz 30°C, 10Hz 30°C, 5Hz 30°C, 1Hz 30°C, 0.5Hz 30°C, 0.1Hz 30°C, 0.01Hz Table 5-4. Summary of the statistical comparisons (mechanical)—Mixture 3MN. Table 5-3. Summary of the statistical comparisons (volumetrics)—Mixture 3MN. (a) Property ComparisonLL-PLR LL-PF PLR-PF AV NA VMA VFA Gmm AC Gsb (b) Property Sieve ComparisonLL-PLR LL-PF PLR-PF Percent Passing 12.5mm 4.75mm 0.600mm 0.075mm

43 Property Comparison LL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR AV NA VMA VFA Gmm AC Gsb (a) (b) Property Sieve Comparison LL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR Aggregate Percent Passing Sieve 12.5mm 4.75mm 0.600mm 0.075mm Table 5-5. Summary of the statistical comparisons (volumetrics)— Mixture 5WI. Property Passes ComparisonLL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR LWT Rut Depth 1,000 5,000 10,000 20,000 Property Temperature, Frequency Comparison LL-PL LL-PLR PL-PLR Axial Dynamic Modulus -10°C, 25Hz -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 4°C, 25Hz 4°C, 10Hz 4°C, 5Hz 4°C, 1Hz 4°C, 0.5Hz 4°C, 0.1Hz 25°C, 25Hz 25°C, 10Hz 25°C, 5Hz 25°C, 1Hz 25°C, 0.5Hz 25°C, 0.1Hz 38°C, 25Hz 38°C, 10Hz 38°C, 5Hz 38°C, 1Hz 38°C, 0.5Hz 38°C, 0.1Hz 54°C, 25Hz 54°C, 10Hz 54°C, 5Hz 54°C, 1Hz 54°C, 0.5Hz 54°C, 0.1Hz (a) (b) Table 5-6. Summary of the statistical comparisons (mechanical)— Mixture 5WI. (continued on next page)

44 Property Comparison LL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR AV NA VMA VFA Gmm AC Gsb Property Sieve Comparison LL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR Aggregate Percent Passing Sieve 12.5 mm 4.75 mm 0.600 mm 0.075 mm (a) (b) Table 5-7. Summary of the statistical comparisons (volumetrics)— Mixture 5LA90. Property Temperature, Frequency Comparison LL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR IDT Dynamic Modulus -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 10°C, 10Hz 10°C, 5Hz 10°C, 1Hz 10°C, 0.5Hz 10°C, 0.1Hz 35°C, 10Hz 35°C, 5Hz 35°C, 1Hz 35°C, 0.5Hz 35°C, 0.1Hz (c) Table 5-6. (Continued).

45 Property Passes ComparisonLL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR LWT Rut Depth 1,000 5,000 10,000 20,000 N/A N/A N/A Property Temperature, Frequency Comparison LL-PL LL-PLR PL-PLR Axial Dynamic Modulus -10°C, 25Hz -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 4°C, 25Hz 4°C, 10Hz 4°C, 5Hz 4°C, 1Hz 4°C, 0.5Hz 4°C, 0.1Hz 25°C, 25Hz 25°C, 10Hz 25°C, 5Hz 25°C, 1Hz 25°C, 0.5Hz 25°C, 0.1Hz 38°C, 25Hz 38°C, 10Hz 38°C, 5Hz 38°C, 1Hz 38°C, 0.5Hz 38°C, 0.1Hz 54°C, 25Hz 54°C, 10Hz 54°C, 5Hz 54°C, 1Hz 54°C, 0.5Hz 54°C, 0.1Hz Property Temperature, Frequency Comparison PL-PF PLR-PF PL-PLR IDT Dynamic Modulus -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 10°C, 10Hz 10°C, 5Hz 10°C, 1Hz 10°C, 0.5Hz 10°C, 0.1Hz 35°C, 10Hz 35°C, 5Hz 35°C, 1Hz 35°C, 0.5Hz 35°C, 0.1Hz (a) (b) (c) Table 5-8. Summary of the statistical comparisons (mechanical)— Mixture 5LA90.

46 5.1.5 Summary of Mixture 5LA61 Analysis Tables 5-9 and 5-10 summarize the statistical comparisons conducted for Mixture 5LA61. Results presented in Table 5-9 indicate that the LL and PL specimens were statistically dif- ferent from the reheated plant-produced specimens (PLR) for most volumetric properties. The main reason for these differences is possibly the low air voids of the PLR speci- mens (average AV for PLR = 3.1%). Differences in mechan- ical properties were also noted among LL, PL, PLR, and PF specimens. 5.1.6 Summary of Mixture 5VA Analysis The following observations are made with respect to the analysis of the test results of Mixture 5VA as summarized in Tables 5-11 and 5-12. The use of hard and low absorption aggregates did not lead to differences in mix gradation or the volumetric properties of the produced mix as compared to the JMF. Rutting performance of the mix in the LWT was excellent for all three specimen types. No stripping was observed for this mixture. Consistent with the mechanical testing of previous mixtures, laboratory-compacted speci- mens exhibited lower average rut depth than field-compacted specimens. Significant differences were observed between LL and PL specimens in axial E* testing. However, there appears to be little practical difference between the specimen types. Indirect tension E* reveals differences among the specimen types. These differences were particularly noted for PL com- parisons, which is consistent with other mixtures tested. 5.1.7 Summary of Mixture 5SD Analysis Results of the analysis of Mixture 5SD, summarized in Tables 5-13 and 5-14, showed that slight differences in gra- dation, while within state tolerances, might lead to signifi- cant differences in important volumetric properties, such as AV and VFA. The use of hydrated lime as an anti-stripping agent appeared to have a pronounced effect on the rutting performance of the mix. Differences in compaction proce- dure and efforts resulted in poor rutting performance for field-compacted specimens. 5.1.8 Summary of Mixture 6FL Analysis Test results of Mixture 6FL showed differences throughout the volumetric and mechanical parameters evaluated. Statis- tical comparisons are summarized in Tables 5-15 and 5-16. With respect to volumetric differences, the deviations were within the acceptable tolerance for most state agencies and the mixtures are, therefore, practically similar. The differences in mechanical values, particularly, dynamic modulus, can be attributed to construction practice followed by the contrac- tor. The mixture was produced during the day and allowed to remain in the silo until production began the same night. This time delay of about 4 to 6 hours may have resulted in additional binder aging, absorption, or both, neither of which was accounted for during laboratory mixing and specimen fabrication. 5.1.9 Summary of Mixture 7IA Analysis Tables 5-17 and 5-18 summarize the statistical comparisons conducted for Mixture 7IA. Statistically significant compari- sons are indicated by a crossed and shaded cell. Table 5-17 indicates that differences appear to be interrelated between the volumetric properties, which may be expected, because these properties depend on each other. Soft aggregates used in this mix did not appear to affect aggregate gradation. On the other Property ComparisonLL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR Air Voids NA VMA VFA Gmm Asphalt Binder Content Gsb Property Sieve ComparisonLL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR Aggregate Percent Passing Sieve 12.5 mm 4.75 mm 0.600 mm 0.075 mm (a) (b) Table 5-9. Summary of the statistical comparisons (volumetrics)— Mixture 5LA61. (text continues on page 52)

47 Property Passes ComparisonLL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR LWT Rut Depth 1,000 5,000 10,000 20,000 Property Temperature, Frequency Comparison LL-PL LL-PLR PL-PLR -10°C, 25Hz -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 4°C, 25Hz 4°C, 10Hz 4°C, 5Hz 4°C, 1Hz 4°C, 0.5Hz 4°C, 0.1Hz D Axial ynamic Modulus 25°C, 25Hz 25°C, 10Hz 25°C, 5Hz 25°C, 1Hz 25°C, 0.5Hz 25°C, 0.1Hz 38°C, 25Hz 38°C, 10Hz 38°C, 5Hz 38°C, 1Hz 38°C, 0.5Hz 38°C, 0.1Hz 54°C, 25Hz 54°C, 10Hz 54°C, 5Hz 54°C, 1Hz 54°C, 0.5Hz 54°C, 0.1Hz Property Temperature, Frequency Comparison LL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR IDT Dynamic Modulus -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 10°C, 10Hz 10°C, 5Hz 10°C, 1Hz 10°C, 0.5Hz 10°C, 0.1Hz 30°C, 10Hz 30°C, 5Hz 30°C, 1Hz 30°C, 0.5Hz 30°C, 0.1Hz (a) (c) (b) Table 5-10. Summary of the statistical comparisons (mechanical)— Mixture 5LA61.

48 (a) Property ComparisonLL-PL LL-PF PL-PF Air Voids NA VMA VFA Gmm Asphalt Binder Content Gsb (b) Property Sieve ComparisonLL-PL LL-PF PL-PF Aggregate Percent Passing Sieve 12.5 mm 4.75 mm 0.600 mm 0.075 mm Table 5-11. Summary of the statistical comparisons (volumetrics)—Mixture 5VA. (a) Property ComparisonLL-PLR LL-PF PLR-PF Air Voids NA VMA VFA Gmm Asphalt Binder Content Gsb (b) Property Sieve ComparisonLL-PLR LL-PF PLR-PF Aggregate Percent Passing Sieve 12.5 mm 4.75 mm 0.600 mm 0.075 mm Table 5-13. Summary of the statistical comparisons (volumetrics)—Mixture 5SD. Property Passes ComparisonLL-PL LL-PF PL-PF LWT Rut Depth 1,000 5,000 10,000 20,000 (a) Property Temperature, Frequency Comparison LL-PL Axial Dynamic Modulus -10°C, 25Hz -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 4°C, 25Hz 4°C, 10Hz 4°C, 5Hz 4°C, 1Hz 4°C, 0.5Hz 4°C, 0.1Hz 25°C, 25Hz 25°C, 10Hz 25°C, 5Hz 25°C, 1Hz 25°C, 0.5Hz 25°C, 0.1Hz 38°C, 25Hz 38°C, 10Hz 38°C, 5Hz 38°C, 1Hz 38°C, 0.5Hz 38°C, 0.1Hz 54°C, 25Hz 54°C, 10Hz 54°C, 5Hz 54°C, 1Hz 54°C, 0.5Hz 54°C, 0.1Hz (b) Property Temperature, Frequency Comparison LL-PF LL-PL PL-PF IDT Dynamic Modulus -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 10°C, 10Hz 10°C, 5Hz 10°C, 1Hz 10°C, 0.5Hz 10°C, 0.1Hz 35°C, 10Hz 35°C, 5Hz 35°C, 1Hz 35°C, 0.5Hz 35°C, 0.1Hz (c) Table 5-12. Summary of the statistical comparisons (mechanical)—Mixture 5VA.

49 Property Passes ComparisonLL-PLR LL-PF PLR-PF LWT Rut Depth (a) 1,000 5,000 10,000 20,000 (b) Comparison Property Temperature, Frequency LL-PLR Axial Dynamic Modulus -10°C, 25Hz -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 4°C, 25Hz 4°C, 10Hz 4°C, 5Hz 4°C, 1Hz 4°C, 0.5Hz 4°C, 0.1Hz 25°C, 25Hz 25°C, 10Hz 25°C, 5Hz 25°C, 1Hz 25°C, 0.5Hz 25°C, 0.1Hz 38°C, 25Hz 38°C, 10Hz 38°C, 5Hz 38°C, 1Hz 38°C, 0.5Hz 38°C, 0.1Hz 54°C, 25Hz 54°C, 10Hz 54°C, 5Hz 54°C, 1Hz 54°C, 0.5Hz 54°C, 0.1Hz Comparison Pr (c) operty Temperature, Frequency LL-PLR LL-PF PLR-PF IDT Dynamic Modulus -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz -10°C, 0.01Hz 10°C, 10Hz 10°C, 5Hz 10°C, 1Hz 10°C, 0.5Hz 10°C, 0.1Hz 10°C, 0.01Hz 30°C, 10Hz 30°C, 5Hz 30°C, 1Hz 30°C, 0.5Hz 30°C, 0.1Hz 30°C, 0.01Hz Table 5-14. Summary of the statistical comparisons (mechanical)—Mixture 5SD. ComparisonProperty LL-PL LL-PF PL-PF Air Voids NA VMA VFA Gmm Asphalt Binder Content Gsb ComparisonProperty Sieve LL-PL LL-PF PL-PF Aggregate Percent Passing Sieve 12.5 mm 4.75 mm 0.600 mm 0.075 mm (a) (b) Table 5-15. Summary of the statistical comparisons (volumetrics)—Mixture 6FL.

50 Co (a) mparisonProperty Passes LL-PL LL-PF PL-PF LWT Rut Depth 1,000 5,000 10,000 20,000 (b) Comparison Property Temperature, Frequency LL-PL -10°C, 25Hz -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 4°C, 25Hz 4°C, 10Hz 4°C, 5Hz 4°C, 1Hz 4°C, 0.5Hz 4°C, 0.1Hz Axial Dynamic Modulus 25°C, 25Hz 25°C, 10Hz 25°C, 5Hz 25°C, 1Hz 25°C, 0.5Hz 25°C, 0.1Hz 38°C, 25Hz 38°C, 10Hz 38°C, 5Hz 38°C, 1Hz 38°C, 0.5Hz 38°C, 0.1Hz 54°C, 25Hz 54°C, 10Hz 54°C, 5Hz 54°C, 1Hz 54°C, 0.5Hz 54°C, 0.1Hz Co (c) mparison Property Temperature, Frequency LL-PL LL-PF PL-PF IDT Dynamic Modulus -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz -10°C, 0.01Hz 10°C, 10Hz 10°C, 5Hz 10°C, 1Hz 10°C, 0.5Hz 10°C, 0.1Hz 10°C, 0.01Hz 30°C, 10Hz 30°C, 5Hz 30°C, 1Hz 30°C, 0.5Hz 30°C, 0.1Hz 30°C, 0.1Hz Table 5-16. Summary of the statistical comparisons (mechanical)—Mixture 6FL. Table 5-17. Summary of the statistical comparisons (volumetrics)— Mixture 7IA. ComparisonProperty LL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR Air Voids NA VMA VFA Gmm Asphalt Binder Content Gsb ComparisonProperty Sieve LL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR Percent Passing 12.5 mm 4.75 mm 0.600 mm 0.075 mm (a) (b)

51 Table 5-18. Summary of the statistical comparisons (mechanical)— Mixture 7IA. ComparisonProperty Passes LL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR LWT Rut Depth 1,000 SIP Comparison Property Temperature, Frequency LL-PL LL-PLR PL-PLR Axial Dynamic Modulus -10°C, 25Hz -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 4°C, 25Hz 4°C, 10Hz 4°C, 5Hz 4°C, 1Hz 4°C, 0.5Hz 4°C, 0.1Hz 25°C, 25Hz 25°C, 10Hz 25°C, 5Hz 25°C, 1Hz 25°C, 0.5Hz 25°C, 0.1Hz 37°C, 25Hz 37°C, 10Hz 37°C, 5Hz 37°C, 1Hz 37°C, 0.5Hz 37°C, 0.1Hz 54°C, 25Hz 54°C, 10Hz 54°C, 5Hz 54°C, 1Hz 54°C, 0.5Hz 54°C, 0.1Hz (a) (b) (continued on next page)

52 hand, all specimen types performed poorly in the LWT test by reaching the tertiary flow region before 5,000 passes. At 1,000 passes, no differences were observed among the speci- men types. In the dynamic modulus test, the main differences were observed between LL specimens when compared to PL and PLR specimens. 5.1.10 Summary of Mixture 8LA Analysis Tables 5-19 and 5-20 summarize the statistical compari- sons conducted for Mixture 8LA. Test results showed that the use of hard and high absorption aggregates (blend absorption is 2.0%) did not substantially affect the mix gradation or the volumetric properties of the produced mix as compared to the JMF. Further, while this mixture was produced with high absorption aggregates, reheating did not influence the VMA or VFA of the produced mix. Rutting performance of the mix in the LWT was excellent for all three specimen types. This behavior is commonly observed for crumb-rubber modi- fied asphalt binder. Consistent with the mechanical testing of previous mixtures, laboratory-compacted specimens had lower average rut depth than field-compacted specimens. No substantial differences were noted between LL and PLR speci- mens in LWT and axial E* testing. 5.2 Combined Statistical Analysis 5.2.1 Effect of Specimen Type on Differences Among Specimen Types Figure 5-1 presents the combined summary of the volu- metric differences observed. The direction of the statistical difference represents whether the relationship was positive or negative. For instance, a negative difference for the LL-PL comparison indicates that the value was significantly greater for the PL specimen when compared to the LL specimen. Co (c) mparison Property Temperature, Frequency LL-PL LL-PLR LL-PF PL-PF PLR-PF PL-PLR IDT Dynamic Modulus -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz -10°C, 0.01Hz 10°C, 10Hz 10°C, 5Hz 10°C, 1Hz 10°C, 0.5Hz 10°C, 0.1Hz 10°C, 0.01Hz 30°C, 10Hz 30°C, 5Hz 30°C, 1Hz 30°C, 0.5Hz 30°C, 0.1Hz 30°C, 0.01Hz Table 5-18. (Continued). ComparisonProperty LL-PLR LL-PF PLR-PF Air Voids NA (a) NA VMA VFA Gmm Asphalt Binder Content Gsb (b) ComparisonProperty Sieve LL-PLR LL-PF PLR-PF Aggregate Percent Passing Sieve 12.5 mm 4.75 mm 0.600 mm 0.075 mm Table 5-19. Summary of the statistical comparisons (volumetrics)—Mixture 8LA.

53 AV, VMA, and VFA were only computed for laboratory- compacted specimens (i.e., LL and PL). Therefore, there are no comparisons involving field-compacted specimens (PF) because the target air voids was different. Figure 5-1 shows the statistical differences that exist for each comparison. How- ever, some of the properties are interrelated. The differences in air voids are mainly attributed to differences within the Gmm measurements. Asphalt binder content resulted in the least amount of statistical difference among the three speci- men types. This was expected, because asphalt binder con- tent is typically well controlled during production. Many of the statistical differences observed were within the tolerance of the test procedure and are, therefore, considered practi- cally equivalent. Table 5-21 summarizes the frequency of statistical and prac- tical differences observed within the combined data set. For example, LL versus PL comparison of air voids was statisti- cally different for 60% of the cases. However, the difference was practically significant for only 20% of the mixtures tested. Practical significance was defined as a measured test difference greater than the d2s precision range reported in the relevant AASHTO test procedure, when available. 5.2.2 Effect of Process-Based Factors on Magnitude of Differences Among Specimen Types An analysis of covariance (ANCOVA) was conducted for each of the volumetric and mechanical properties evaluated in the study. Table 5-22 presents the results of the ANCOVA conducted on the volumetric properties. The highlighted cells indicate a statistically significant effect of a process-based fac- tor on a specific volumetric property. As shown in this table, the effects of process-based factors on the differences between production (PL) and construction (PF) specimens were mini- mal. This is reasonable, given the similarity between these two specimen types (e.g., baghouse is used in both PL and PF specimens). The effect of time delay of specimen fabrication Comparison (a) Property Passes LL-PLR LL-PF PLR-PF LWT Rut Depth 1,000 5,000 10,000 20,000 (b) Comparison Property Temperature, Frequency LL-PLR -10°C, 25Hz -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz 4°C, 25Hz 4°C, 10Hz 4°C, 5Hz 4°C, 1Hz 4°C, 0.5Hz 4°C, 0.1Hz Axial Dynamic Modulus 25°C, 25Hz 25°C, 10Hz 25°C, 5Hz 25°C, 1Hz 25°C, 0.5Hz 25°C, 0.1Hz 38°C, 25Hz 38°C, 10Hz 38°C, 5Hz 38°C, 1Hz 38°C, 0.5Hz 38°C, 0.1Hz 54°C, 25Hz 54°C, 10Hz 54°C, 5Hz 54°C, 1Hz 54°C, 0.5Hz 54°C, 0.1Hz Comparison (c) Property Temperature, Frequency LL-PLR LL-PF PLR-PF IDT Dynamic Modulus -10°C, 10Hz -10°C, 5Hz -10°C, 1Hz -10°C, 0.5Hz -10°C, 0.1Hz -10°C, 0.01Hz 10°C, 10Hz 10°C, 5Hz 10°C, 1Hz 10°C, 0.5Hz 10°C, 0.1Hz 10°C, 0.01Hz 30°C, 10Hz 30°C, 5Hz 30°C, 1Hz 30°C, 0.5Hz 30°C, 0.1Hz 30°C, 0.01Hz Table 5-20. Summary of the statistical comparisons (mechanical)—Mixture 8LA.

54 a) Air Voids b) VMA c) VFA d) Asphalt Binder Content e) Gmm f) Gsb 0 2 4 6 8 10 - = + - = + - = + Fr eq ue nc y Difference LL-PF N/A LL-PL PL-PF N/A 0 2 4 6 8 10 - = + - = + - = + Fr eq ue nc y Difference LL-PF N/A LL-PL PL-PF N/A 0 2 4 6 8 10 - = + - = + - = + Fr eq ue nc y Difference LL-PF N/A LL-PL PL-PF N/A 0 2 4 6 8 10 12 - = + - = + - = + Fr eq ue nc y Difference LL-PF LL-PL PL-PF LL-PF LL-PF LL-PL LL-PL PL-PF PL-PF 0 2 4 6 8 10 12 - = + - = + - = + Fr eq ue nc y Difference 0 2 4 6 8 10 - = + - = + - = + Fr eq ue nc y Difference Figure 5-1. Summary of the statistical comparisons (volumetric)—combined. Comparison % Stastically Different / % Praccally Different Air Voids VMA VFA Gmm AC Gsb LL vs. PF ---- ---- ---- 50% / 20% 10% / 0% 20% / 20% LL vs. PL 60% / 20% 30% / 10% 80% / 50% 50% / 10% 20% / 20% 40% / 10% PL vs. PF ---- ---- ---- 30% / 20% 10% / 10% 10% / 10% Table 5-21. Summary of the statistical comparisons (volumetric)— combined.

55 was not significant in any comparison. Significant factors in the analysis are summarized below: • The return of baghouse fines showed a statistically signifi- cant effect on AC as well as gradation. • Aggregate absorption showed a statistically significant effect on AC between design and production specimens. • Aggregate hardness had a statistically significant effect on gradation between laboratory-mixed and plant-produced specimens. • Stockpile moisture had a significant effect on the measured air voids between design and production specimens. Table 5-23 presents the results of the ANCOVA for the mechanical properties. Only one effect of process-based fac- tors on the differences among specimen types for the mechan- ical properties was noted. Aggregate hardness was statistically significant for IDT dynamic modulus between design (LL) and construction (PF) specimens. Results of the meta-analysis for the mechanical properties also showed that there is no sta- tistically significant effect due to time delay in specimen fab- rication. The lack of observed effects of process-based factors may result from the variations in the mechanical properties being strongly controlled by compaction effort. Many of the individual mixture comparisons showed that field-compacted specimens (PF) were significantly different from laboratory- compacted specimens (LL and PL). This finding was attributed to differences in compaction effort and confinement condi- tions between the two compaction processes (laboratory and field). In addition, differences in aggregate orientation due Comparison Parameter Baghouse TimeDelay Aggregate Absorption Aggregate Hardness Stockpile Moisture Design (LL) - Production (PL) Air Voids VMA VFA AC Gmm Gsb Gradation Design (LL) - Construction (PF) AC Gmm Gsb Gradation Production (PL) - Construction (PF) AC Gmm Gsb Gradation Table 5-22. Summary of the ANCOVA—volumetric properties. Comparison Parameter Baghouse TimeDelay Aggregate Absorption Aggregate Hardness Stockpile Moisture Design (LL) - Production (PL) LWT Axial Dynamic Modulus IDT Dynamic Modulus Design (LL) - Construction (PF) LWT IDT Dynamic Modulus Production (PL) - Construction (PF) LWT IDT Dynamic Modulus Table 5-23. Summary of the ANCOVA—mechanical properties.

56 to compaction efforts may affect the mechanical properties deviations among specimen types. Results from a nationwide survey of contractors and agen- cies conducted in this research suggest that competent con- tractors understand how to control the process-based factors affecting their mixture during production. For example, sev- eral contractors incorporate baghouse dust into their mixture design process when the baghouse dust is to be returned dur- ing production. Further, contractors that use soft or absorptive aggregate account for aggregate breakdown during the mix- ture design process by increasing the quantity of fine aggregate. Figures 5-2 through 5-5 present the results of the nationwide contractor survey on the effects of process-based factor dur- ing production and design. The figures indicate that contrac- tors sufficiently understand how their materials will change through the production process. For instance, VMA collapse is often reduced by fine-tuning the production process. VMA collapse is the loss of VMA during plant production of asphalt mixtures. 5.2.3 Effects of Specimen Type on Measured Dynamic Modulus Figure 5-6 presents two typical master curves constructed from the indirect dynamic modulus data for the three speci- men types. As shown in this figure, the dynamic modulus of field-compacted specimens (PF) was generally lower than that of laboratory-compacted specimens. This difference is com- monly attributed to differences in compaction effort and aggre- gate orientation between lab and field compaction. Figure 5-6 also shows that the dynamic modulus of the plant-produced mixture (PL) was generally stiffer than or similar to that of the laboratory-mixed specimens (LL). This may be attributed to the hardening of the binder at the plant as compared to the laboratory, since the indirect tensile strength test is very sensi- tive to the binder stiffness. Figure 5-7 compares the laboratory-measured dynamic modulus among the three specimen types evaluated and pre- sents the percentage difference among the average modulus values normalized with respect to the plant production speci- mens (PL). Normalization allows comparisons to be made among the ten mixtures tested by removing the influence of varying characteristics (e.g., binder grade, binder content, and gradation). Typically, the construction specimens yielded a lower modulus value (indicated by a positive bar) than the laboratory-compacted specimens. As shown in Figure 5-7, the largest differences were observed for the comparisons involving field-compacted (i.e., PF) specimens. This may be attributed to differences in particle orientation and compac- tion effort between field- and laboratory-compacted speci- mens. Figures 5-6 and 5-7 show that the percentage difference increased with testing temperature. Further, the specimens fabricated with plant-produced mixture (PL) were generally stiffer than those of laboratory-produced mixture (LL). Figure 5-2. Question 5 re Baghouse fines used during mixture design. Yes, 70% No, 30% Figure 5-3. Question 6 re Account for plant breakdown during mixture design. Yes 88% No 12% Figure 5-4. Question 7 re VMA collapse prior to fine-tuning. Yes 61% No 39% Figure 5-5. Question 8 re VMA collapse after fine-tuning. Yes 22% No 78%

57 Figure 5-6. IDT E*—Master curve comparison. (a) Mix 3MN 0 5000 10000 15000 20000 25000 1.0E-03 1.0E+00 1.0E+03 1.0E+06 Co m pl ex M od ul us , M pa Reduced Frequency LL PL PF (b) Mix 5VA 0 5000 10000 15000 20000 25000 1.0E-04 1.0E+00 1.0E+04 Co m pl ex M od ul us , M pa Reduced Frequency LL PL PF Figure 5-7. IDT E* delta comparison—delta modulus/PL modulus. (a) Low-Temperature Comparison, -10°C (b) Intermediate-Temperature Comparison, 10°C (c) High-Temperature Comparison, 25-35°C -40.0% -20.0% 0.0% 20.0% 40.0% 1WI 3MN 5LA61 5MI 5SD 5VA 5WI 6FL 7IA 8LA Pe rc en t D iff er en ce Mixture LL vs. PL LL vs. PF PL vs. PF -60.0% -30.0% 0.0% 30.0% 60.0% 1WI 3MN 5LA61 5MI 5SD 5VA 5WI 6FL 7IA 8LA Pe rc en t D iff er en ce Mixture LL vs. PL LL vs. PF PL vs. PF -80.0% -40.0% 0.0% 40.0% 80.0% 1WI 3MN 5LA61 5MI 5SD 5VA 5WI 6FL 7IA 8LA Pe rc en t D iff er en ce Mixture LL vs. PL LL vs. PF PL vs. PF

58 Table 5-24 presents the absolute value (averages, mini- mums, and maximums) of the percent differences for the comparisons. The table shows that, as the testing tempera- ture increases, the mean percent difference also increases and that the comparisons of the core specimens, PF, with the LL samples resulted in the largest differences for each tempera- ture region. The maximum difference of 78% observed was for PL vs. PF at 25 to 35°C. ANOVA with a significance level of a = 0.05 was used to determine statistical significance. Within the ANOVA, indi- vidual pair-wise comparisons (i.e., PL vs. LL, PL vs. PF, and LL vs. PF) were conducted using Duncan’s MCT. Figure 5-8 Table 5-24. Descriptive statistics—delta modulus/ PL modulus. Temperature, °C Comparison Mean, % Minimum, % Maximum, % -10 LL vs. PL 7 1 14 LL vs. PF 11 2 25 PL vs. PF 15 1 37 10 LL vs. PL 12 3 49 LL vs. PF 16 2 34 PL vs. PF 22 4 54 25-35 LL vs. PL 25 11 58 LL vs. PF 26 1 76 PL vs. PF 35 4 78 Figure 5-8. Histogram of IDT E* statistical differences. (a) Low-Temperature Comparison, -10°C (b) Intermediate-Temperature Comparison, 10°C (c) High-Temperature Comparison, 25-35°C 0 20 40 60 80 100 - = + - = + - = + Pe rc en ta ge D iff er en ce s Difference LL-PF LL-PL PL-PF 0 20 40 60 80 100 - = + - = + - = + Pe rc en ta ge D iff er en ce s Difference PL-PF LL-PL LL-PF 0 20 40 60 80 100 - = + - = + - = + Pe rc en ta ge D iff er en ce s Difference LL-PL PL-PF LL-PF

59 Figure 5-9. IDT E* statistical summary. 32 34 16 44 48 56 28 58 60 62 46 71 0 10 20 30 40 50 60 70 80 90 100 Overall LL vs. PF LL vs. PL PL vs. PF Pe rc en ta ge o f D iff er en ce s Comparison Low Temp Intermediate Temp High Temp presents the results of the ANOVA. The histogram repre- sents the percentages of statistical differences observed. The bars indicate the direction of the statistical differences. For the -10°C comparisons in Figure 5-8, the design LL modulus was significantly greater than the PF core modu- lus in 28% of the comparisons. The statistical comparisons among the three specimen types showed statistical differ- ences among all specimen types, especially at intermediate and high temperatures. The least difference was observed at low temperature. Further, the PF samples (field cores) yielded significantly lower values than the LL (laboratory- compacted) specimens. Figure 5-9 presents the percentage of statistically significant differences observed for each comparison. The figure shows that the LL versus PL comparison resulted in the fewest per- centages of statistically significant differences. In contrast, comparisons that included PF specimens resulted in statisti- cally significant differences for over 50% of the cases. The per- centage of statistically significant differences increased with the increase in testing temperature.