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8.4 Summary and Conclusions on CRM-Asphalt Interaction A series of rheological property tests and chemical analyses were conducted on — Figure 125 8.4 Summary and Conclusions on CRM-Asphalt Interaction A series of rheological property tests and chemical analyses were conducted on

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purposes is one practical solution (Mashaan et al. 2014). Crumb rubber modifier (CRM), sometimes referred to as ground tire rubber (GTR), landfills is not. Recycling tire-derived aggregates and crumb rubbers for construction vith them, retreading and recycling are environmentally friendly, while putting them into

Figure 2-2. Ambient ground rubber (left); cryogenically fractured rubber (right) (Shen & Amikhanian 2005)

modification of asphalt in a continuous blend system at an asphalt mix plant. Figure 2-3. CR modification of asphalt in a continuous blend system (http://maxlinktyrerecycling.com)

Figure 2-4. Feed system for the dry process (Hines 2007) In 1950, the use of CRM in asphalt as a stress-absorbing membrane interlayer and open- graded mixtures (Heitzman 1992). Figure 2-4 shows the feed system used for

Table 2-1. Some applications of dry-processed CRM asphalt mixtures by state

Table 2-2. Some applications of wet-processed CRM asphalt mixtures by state

Figure 2-5. Asphalt rubber (left); terminal blends (right) 9-10% CRM weight of total binder. Terminal blends look different from traditionally particulate matter remaining. Sometimes, polymers are added with fine CRM, typically at

Figure 3-1. Flow chart for testing rubberized asphalt binder properties asphalt binder to evaluate the effects (Fig. 3-1). DSR, BBR, and separation tests were then conducted on unaged and aged rubberized

Aging was accelerated in the standard rolling thin-film oven (RTFO) at 163 °C for 85

Figure 3-2. CRM (left) and TOR (right) binder was mixed at 170 °C and 900 RPM for 45 minutes in the laboratory. Table 3-1

Figure 3-5. Dynamic shear rheometer

The separation tube test was performed to determine CRM tendency to separate

specimens. Tendency of Polymer from Polymer Modified Asphalt. Figure 3-7 shows th

Figure 3-8 shows the values of G*/sin(5) and phase angle at 76 °C for the binders temperatures, a complex shear modulus and phase angle were measured for both

Note: Y: P-value < a = .05 (significant difference); N: P-value > o = .05 (no significant difference). The phase angle of the unaged rubberized asphalt binders decreased as the dose of asphalt binder. It also increased as CRM dose increased from 8% to 12%, regardless

Note: Y: P-value < a = .05 (significant difference); N: P-value > a = .05 (no significant difference).

Table 3-3. Statistical analysis of the phase angle of unaged rubberized asphalt binders

PG grades (12.0 °C) at high temperature, regardless of the type of base asphalt.

“or an RTFO-aged rubberized asphalt binder consisting of a PG 67-22 asphalt and 8%

For RTFO-aged, rubberized asphalt binder consisting of a PG 67-22 base binder increased as CRM dose increased from 8% to 12%, regardless of TOR dose and base

Figure 3-14. m-values of PAV -aged rubberized asphalt binder at -12 °C 3.3.3 Effect of TOR on separation resistance

to some extent, TOR reduces separation severity in rubberized asphalt binder. 3.4 Summary and Conclusions for Rubberized Binder Properties

properties with both dry- and wet-processed CRM binders (Fig. 4-1). 4,2 Materials and Test Procedures

Table 4-1. Properties of materials used Table 4-2. Properties of cellulose fibers* the materials tested.

* The data are from the manufacturer, Fiberand, Inc. (Miami, FL).

Table 4-3. Properties of mineral fibers* Figure 4-2. Mineral fibers

These materials were combined to produce gradations similar to those for

Figure 4-4. A ggregate gradations of PEM and SMA used for this study Specifications, Section 828. gradations meet the control tolerances and design criteria of the Standard

Table 4-5. Surface-capacity test results

Figure 4-5. Surface-capacity test

Modified Marshall Method Dry-processed PEM is mixed in the following steps: (1) aggregates are mixed with

Table 4-6. Asphalt content as determined by the modified Marshall method determined as the value at which V MA reached the lowest point on the curve plot.

Drain-down test

Table 4-7. Results of drain-down testing Table 4-8. Volumetric properties of PEMs 4-8 presents the OAC and other volumetric properties of the four PEM.

Note: OAC = optimal asphalt content; Gm = maximal specific gravity; Gmb = bulk specific gravity; AV =air voids; VMA = voids in mineral aggregate; VFA = voids filled with asphalt. Based on these tests, the final OAC was 6.5% for wet-processed rubberized

Note: OAC = optimal asphalt content; Gmm = maximal specific gravity; AV = air voids; VMA =voids in mineral aggregate; VFA = voids filled with asphalt.

Table 4-9. Volumetric properties of SMA mixtures mixtures at OAC. Marshall hammer (Fig. 4-8). Table 4-9 presents the volumetric properties for all SMA

steel wheel on a pneumatic hose at 100 psi of pressure for 8,000 cycles. Figure 4-9. APA Test

respectively. Figure 4-11. SMA average rut depths

Figure 4-10. PEM average rut depths

Figures 4-13 and 4-14 show the results for PEM and SMA samples. Rutting depth

Table 4-10. Results of drain-down testing drain-down while the others had none.

and placed in a foil pan for transfer into a 177 °C +2 °C oven (Fig. 4-15).

4.5 Summary and Conclusions for Mix Design Verification The volumetric properties of both PEM and SMA mixed with wet- and dry-processed

Table 5-1. Dynamic modulus test matrix collected. Figure 5-1 presents a flow chart of testing. E* were measured at different and a typical aggregate granite used by GDOT. Table 5-1 shows the types of date

Figure 5-1. Flow chart for determining the dynamic moduli of rubberized PEM and 5,2 Materials and Test Procedures mixture specimens used in this study had target air voids of 170.5% and 5+0.5%,

Figure 5-2. Gyratory compaction of PEM and SMA specimens 0.1 Hz, 1 Hz, 10 Hz) for 18 hours at 4 °C, 3 hours at 20 °C, and 3 hours at 45 °C.

Figure 5-3. Specimen coring and cutting Dynamic modulus testing was conducted for each PEM and SMA mixture with an

Figure 5-4. Dynamic modulus samples and conditioning

Figure 5-5. AMPT device and instrumentation 5.3 Results and Discussions

asphalt binder types at 45 °C was 90-92% lower than at 4 °C.

Figure 5-6. PEM dynamic modulus vs. temperature at 10 Hz

Figure 5-8. PEM dynamic modulus vs. temperature at 0.1 Hz Dynamic modulus dependence on load frequency frequency. Under a constant test temperature, the dynamic moduli of all PEM

Figure 5-9. PEM dynamic modulus vs. frequency at 45 °C

20 °C; and slightly lower than hybrid and SBS-modified PEM at 4 °C.

Figure 5-14. PEM phase angle vs. temperature at 0.1 Hz Figure 5-13. PEM phase angle vs. temperature at 1 Hz

Master curve of dynamic moduli Master curves of asphalt mixtures allow performance comparisons over extended

To determine whether dry-processed rubberized PEM performs as well as the dynamic modulus; 6 +a = maximum value of dynamic modulus; and B, y = parameter

Note: Y: P-value < o = .05 (significant difference); N: P-value > a = .05 (no significant difference). Table 5-2. Statistical analysis of PEM dynamic modulus Master curve of phase angles [he master curve of the phase angles of four PEM mixtures (Fig. 5-19) shows that the

5.3.2 SMA dynamic modulus and phase angle

modulus at low frequency and high temperature (0.01 or 0.1Hz at 45 °C).

Figure 5-22. SMA dynamic modulus vs. temperature at 0.1 Hz

Figure 5-23. SMA dynamic modulus vs. frequency at 45 °C

Master curve of dynamic moduli

Note: Y: P-value < a = 0.05 (significant difference); N: P-value > a =0 .05 (no significant difference).

Table 5-3. Statistical analysis of SMA dynamic modulus

samples decreased with increased frequency, while at 45 °C, they increased.

Note: Y: P-value < o = .05 (significant difference); N: P-value > a = .05 (no significant difference). Table 5-4. Statistical analysis of SMA phase angle 5.4 Summary and Conclusions on Dynamic Modulus The effect on the dynamic modulus of modifying PEM and SMA mixtures four

Figure 6-1. Flow chart for determining the fatigue life of rubberized PEM and SMA 6.2 Specimen Fabrication and Test Procedures

Figure 6-2. Specimen fabrication S-VECD Direct Tension F atigue Test

7.2 Materials and Test Procedures

Figure 7-2. Georgia asphalt weathering device

Figure 7-3. |E*| master curves: (a) unaged and 1000-hour aging; (b) unaged and 3000-hour aging Furthermore, a t-test (a = 0.05) was performed to compare |E*| between aging

factors (Figure 7-4). The ratio of |E*| between the long-term aged and unaged specimens can elucidate the PEM samples, indicating that it foamed due to the interaction of the environment

Figure 7-6. Modular aging ratio for wet- processed rubberized PEM

Figures 7-5 to 7-8 indicate that both AR1 and AR2 for all PEM mixtures increased

on |E*| at lower frequency (0.1 Hz) or higher temperature (45 °C). Figures 7-10 to 7-13 show aging ratio (AR) results for all SMA mixtures. Both etween unaged and 1,000-hour aging, but 3,000-hour aging had a significant effect

Figure 7-10. Modular aging ratio for dry-processed rubberized SMAs mixes after 1,000- or 3,000-hour weathering.

Figure 7-11. Modular aging ratio for wet- processed rubberized SMAs

7.3.3 Influence of weathering on fatigue life jor damage throughout the test. End-failure tests are not as good since

Figure 7-14. Failure locations: (a) mid-failure; (b) end-failure (Hou 2009) more end-failures than unaged samples; few unaged samples had end-failures. had mid-failures; the CX test was successful. It also found that aged samples had

Figure 7-15. SMA fatigue life under strain control after 3,000-hour aging

depth, regardless of aging. Figure 7-18 shows the rutting depth results for unaged and aged SMA mixtures. As SBS-modified PEM mixtures. Furthermore, hybrid PEM mix had the lowest rutting samples, dry-processed CRM SMA had the deepest rutting followed by SBS-modified

7.3.9 Influence of weathering on C antabro loss SMA, like hybrid PEM, had the least rutting, regardless of aging.

7.3.6 Influence of weathering on indirect tensile strength

Figures 7-22 and 7-23 illustrate the IDT results for unaged and aged PEM and

nano-structure characteristics. Figure 8-1 shows the experimental design.

using the centrifuge extractor and tetrahydrofuran (THF) as the solvent.

Figure 8-3. Separated asphalt binder and THF Gel Permeation Chromatography

Figure 8-4. GPC system used in this study manufacturer. Each binder sample, dissolved in THF, went through a 0.45-um syringe filter prior concentration rate was 0.5% by weight of binder as recommended by the equipment

Figure 8-5. A typical chromatogram of an asphalt binder proximately 21 minutes (Fig. 8-5). Each sample was tested three times, and the In Figure 8-5, the area under the curve represents 100% of the binder molecules to the injection module. A sample volume of 50 ul was injected for each test, which several groups. In this study, the chromatogram profile was partitioned into 13 slices

Table 8-1. Assignments of the main bands of asphalt binder in FTIR spectra

Figure 8-6. FTIR system used in this study

Figure 8-7. G* of asphalt binder extracted from rubberized PEM highest value. Binders extracted from mixtures stored for 30 minutes had the same G* increased their G*, and binder extracted from 90-minute aged mixtures had the

Table 8-2. Statistical analysis of G* of asphalt binder from rubberized PEM All binders were tested at 76 ‘C and thus exhibit viscoelasitc properties. As

Figure 8-8. Phase angle of asphalt binders extracted from rubberized PEM recovered binders stored for 30 minutes, indicating that their elasticity is equivalent.

Table 8-3. Statistical analysis of phase angles of binders from rubberized PEM Figure 8-9 shows that the G*/sinéd value of binders extracted from dry-processed

Figure 8-9. Rutting resistance of asphalt binders extracted from rubberized PEM thus, their rutting resistance is equivalent. rubberized PEM stored for 30 minutes had the same value as the wet-processed and

Table 8-4. Statistical analysis of asphalt binder rutting resistance and binder results in a stiffer asphalt binder due to dry-process mixing and aging.

Figure 8-10. LMS of asphalt binder extracted from rubberized PEM FTIR results Figure 8-11 shows infrared (IR) spectrum analysis images of four asphalt binders

Figure 8-11. FTIR spectra of CRM asphalt extracted from rubberized PEM

Table 8-5. Statistical analysis of the G* of asphalt binder from rubberized SMA after 90 minutes’ storage and wet-processed SMA was found.

Figure 8-13. G* of asphalt binder extracted from rubberized SMA same level. that the G* of asphalt binder in dry- and wet-processed rubberized SMA can reach the Table 8-5 shows the results of a one-way analysis of variance of the significance

Table 8-6. Statistical analysis of phase angle of binder from rubberized SMA

Figure 8-14. Phase angle of asphalt binder extracted from SMA Table 8-6 indicates no significant difference between asphalt binders extracted after 90 minutes’ storage was lowest. For the binders tested, longer storage increases oinder. The phase angle of binders extracted from dry-processed rubberized SMA

Note: S=significant difference; N=no significant difference; significance level=0.05 Figure 8-15 shows that the G*/siné value of binders extracted from dry-processed

Figure 8-15. Rutting resistance of binder extracted from rubberized SMA in dry-processed rubberized SMA reach a level similar to that of wet-processed.

Table 8-7. Statistical analysis of asphalt binder rutting resistance

Figure 8-16. LMS of asphalt binder extracted from rubberized SMA dry-processed rubberized SMA based on the GPC test as a function of aging time. Figure 8-16 shows the LMS values of control and binders extracted from a loose FTIR results

Figure 8-17. FTIR spectra of CRM asphalt extracted from rubberized SMA

Figure 8-18. Bonding ratio (C=O) in CRM asphalt extracted from dry- and to that of wet-processed SMA. wet-processed rubberized SMA dry-processed CRM SMA mixture increases with storage. After 30 minutes, it is close

were used in the AFM tapping mode to avoid damaging the asphalt binder surface Wet- processed rubberized asphalt binder was produced by mixing -30 mesh CRM

Figure 8-20. Topographic and phase images of PG 67-2:

Figure 8-21. Phase images of unaged rubberized asphalt binders

Figure 8-22. Phase images of short-term aged rubberized asphalt binders

dry- processed rubberized CRM asphalt binder and least in SBS asphalt binder. GPC results

Figure 9-2. LMS of asphalt binder extracted from PEM and lightweight elements, reducing the LMS value change. FTIR results asphalt binder production process, the rubbers absorb the asphalt binder’s resin, oil Figure 9-3 shows the infrared (IR) spectrum analysis of four asphalt binders extracted

Figure 9-4. Bonding ratio (C=O) of asphalt binder extracted from rubberized PEM photo-oxidation, and other uncontrolled natural phenomena influence the nature and depending on weathering time and asphalt binder type. Evaporation, leachins 9.3.2 Effect of weathering on asphalt binder in SMA

Figure 9-5, G*sin(8) (at 19 °C) of asphalt binder extracted from SMA and wet- processed rubberized CRM asphalt binder was almost identical. GPC results

FTIR results

onhancement after weathering 1,000 hours.

Figure 9-7 shows the ratio change (C=O) in the asphalt binder extracted from four

Figure 9-7. Ratio of bonding (C=O) of asphalt binder extracted from SMA

stringline using a hollow steel pipe (Fig. 10-2).

Table 10-1. Field inspection test results

Figure 10-4. Dry-processed rubberized OGFC surface

The Hamburg test using a retrofitted APA was performed on the core samples

Figure 10-8. Field core specimens forA PA Hamburg testing Mixtures showing excessive susceptibility to moisture damage tend to undergo

Figure 10-9. Two different outputs of the HWTD test (Bhasin et al. 2004) rutting depth of 12.5 mm indicate less susceptibility to moisture damage.

Figure 10-10. Stripping point determination

Table 10-2. Rut depth per number of wheel passes

Table 10-3. Summary of test results

‘igure 10-13 present the values of post-compaction consolidation and creep slope.

The core samples with dry- or wet-processed rubberized OGFC had significantly

Table 10-4. Rates of rutting at the two-cycle interval