Evaluation of Nevada s Warm Mix Asphalt Mixtures with Recycled Asphalt Pavements.

Transcription

1 University of Nevada, Reno Evaluation of Nevada s Warm Mix Asphalt Mixtures with Recycled Asphalt Pavements. A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Civil and Environmental Engineering By Balasekaram Jayaprakas Dr. Peter E. Sebaaly/ Thesis Advisor August, 2016

2 THE GRADUATE SCHOOL We recommend that the thesis prepared under our supervision by Balasekaram Jayaprakas entitled Evaluation of Nevada s Warm Mix Asphalt Mixtures with Recycled Asphalt Pavements be accepted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Peter E. Sebaaly, Ph.D., Advisor Elie Y. Hajj, Ph.D., Committee Member Mariah Evans, Ph.D., Graduate School Representative David W Zeh, Ph.D., Graduate Dean, Graduate School August, 2016

3 i ABSTRACT The purpose of this study is to evaluate warm mix asphalts (WMA) with recycled asphalt pavement (RAP) from Nevada. For this study, four different warm mix technologies and four different aggregate sources with two different percentages of recycled asphalt binder ratios were used. Aggregates from Lone Mountain, North Tenaya, Spanish Springs and Lockwood were used with appropriate binders for the particular climate conditions in those areas. All the aggregates were lime-marinated, as per requirement of the Nevada Department of Transportation. Advera, Evotherm 3G, Sonnewax and waterfoam were the warm mix technologies evaluated. All four WMA mixtures satisfied all the criteria for resistance to moisture damage with or without RAP for all the aggregate sources used. In terms of fatigue, the WMA mixtures showed better results than the HMA mixture. But for the rutting resistance all of the WMA mixtures showed lower values than the HMA mixtures. This was expected, even though the WMA s rutting resistance improved when RAP was added.

4 ii ACKNOWLEDGMENTS I would like to extend my heartfelt gratitude and appreciation to the people who helped me to complete this study. First of all, I would like to thank Dr. Peter Sebaaly sincerely for giving me a great opportunity, guidance, advice and encouragement to do research work in timely manner. I also would like to express my sincere thanks to Dr. Elie Hajj for guidance, advice and encouragement in my career advancement. I would like to express my heartfelt thanks to Dr. Raj Siddharthan, Dr. Nathaniel E. Morian and Mr. M. Piratheepan for guiding me and helping me to perform well in my research and studies. I would like to express the deepest appreciation to Dr. Mariah Evans for being a member in my thesis committee. I also would like to thank my colleagues at UNR for all their support during my stay at University of Nevada, Reno. This research was supported by Nevada Department of Transportation and their support is acknowledged. Last, but not least, I would like to express my sincere thanks to my parents, sisters, brothers and brother in law for their continuous support and encouragement throughout my life, which helped me to achieve all my goals in my studies and life.

5 iii TABLE OF CONTENTS University of Nevada, Reno... 1 ABSTRACT... i ACKNOWLEDGMENTS... ii List of Tables... v List of Figures... vi Chapter 1: Introduction Objective... 1 Chapter 2: Warm mix technologies Advera Evotherm SonneWarmix Water Foaming Warm Mix Asphalt with RAP... 5 Chapter 3: Material Sources Aggregate Sources Asphalt Binders RAP... 7 Chapter 4: Experimental Plan Superpave PG System Hveem Mix Design Coating of WMA mixtures Compactability of WMA Mixtures Indirect Tensile Strength Engineering Properties... 16

6 iv 4.7 Resistance to Rutting Fatigue Analysis-Flexural beam fatigue test Chapter 5: Test Results and Analysis Binder Characterization RAP Characterization Mix Design Details Engineering Properties Resistance to Moisture Damage: Tensile Strength Engineering Property: Dynamic Modulus Resitance to Rutting: Flow Number Resistance to Fatigue: Flexural Beam Chapter 6: Conclusions and Recommendations Impact of RAP Materials Impact of WMA Additives Chapter 7: References Appendix A: Tables Appendix B: Figures... 58

7 v List of Tables Table 1: RAP binder properties Table2: Experimental plan Table 3: Performance tests Table 4: Properties of the PG76-22NV Asphalt Binder Table 5: Properties of the PG64-28NV Asphalt Binder Table 6: Gradations of the Lone mountain aggregates Table 7: Gradations of the North Tenaya Aggregates Table 8: Gradations of the Spanish Spring Aggregates Table 9: Gradations of the Lockwood Aggregates Table 10: Mix Design for the Lone Mountain Aggregates with 0% RAP Binder Ratio Table 11: Mix Design for the Lone Mountain Aggregates with 15% RAP Binder Ratio. 51 Table 12: Mix Design for the North Tenaya Aggregates with 0% RAP Binder Ratio Table 13: Mix Design for the North Tenaya Aggregates with 15 % RAP Binder Ratio.. 53 Table 14: Mix Design for the Spanish Spring Aggregates with 0 % RAP Binder Ratio.. 54 Table 15: Mix Design for the Spanish Spring Aggregates with 15 % RAP Binder Ratio Table 16: Mix Design for the Lockwood Aggregates with 0 % RAP Binder Ratio Table 17: Mix Design for the Lockwood Aggregates with 15 % RAP Binder Ratio

8 vi List of Figures Figure 1: Testing setup for dynamic modulus in AMPT machine Figure 2: Dynamic Modulus master curve Figure 3: Cumulative permanent axial strain with respect to number of cycles in the flow number test Figure 4: Testing setup for flexural beam test Figure 5: Typical curve for flexural stiffness ratio Figure 6: Tensile strength at 0 and 1 F-T for Southern Nevada mixtures Figure 7: Tensile strength at 0 and 1 F-T for Northern Nevada mixtures Figure 8: Tensile strength ratio for Southern Nevada mixtures Figure 9: Tensile strength ratio for Northern Nevada mixtures Figure 10: Dynamic Modulus at 0 and 1 F-T for the Southern Mixtures Figure 11: Dynamic Modulus at 0 and 1 F-T for the Northern Mixtures Figure 12: Dynamic Modulus (E*) Master Curves for Lone Mountain mixes with 0 % RAP at 0 FT Figure 13: Dynamic Modulus (E*) Master Curves for Lone Mountain mixes with 0 % RAP at 1 FT Figure 14: Dynamic Modulus (E*) Master Curves for Lone Mountain mixes with 15 % RAP at 0 FT Figure 15: Dynamic Modulus (E*) Master Curves for Lone Mountain mixes with 15 % RAP at 1 FT Figure 16: Dynamic Modulus (E*) Master Curves for North Tenaya mixes with 0 % RAP at 0 FT Figure 17: Dynamic Modulus (E*) Master Curves for North Tenaya mixes with 0 % RAP at 1 FT Figure 18: Dynamic Modulus (E*) Master Curves for North Tenaya mixes with 15 % RAP at 0 FT Figure 19: Dynamic Modulus (E*) Master Curves for North Tenaya mixes with 15 % RAP at 1 FT Figure 20: Dynamic Modulus (E*) Master Curves for Spanish Springs with 0 % RAP at 0 FT.. 65

9 vii Figure 21: Dynamic Modulus (E*) Master Curves for Spanish Springs with 0 % RAP at 1 FT.. 65 Figure 22: Dynamic Modulus (E*) Master Curves for Spanish Springs with 15 % RAP at 0 FT. 66 Figure 23: Dynamic Modulus (E*) Master Curves for Spanish Springs with 15 % RAP at 1 FT. 66 Figure 24: Dynamic Modulus (E*) Master Curves for Lockwood with 0 % RAP at 0 FT Figure 25: Dynamic Modulus (E*) Master Curves for Lockwood with 0 % RAP at 1 FT Figure 26: Dynamic Modulus (E*) Master Curves for Lockwood mixes with 15 % RAP at 0 FT Figure 27: Dynamic Modulus (E*) Master Curves for Lockwood mixes with 15 % RAP at 1 FT Figure 28: Flow number values for Southern mixes Figure 29: Flow number values for Northern mixes Figure 30: Number of cycles to failure for Southern mixes at 70 F and 700 micro strains Figure 31: Number of cycles to failure for Southern mixes at 70 F and 400 micro strains Figure 32: Number of cycles to failure for Northern mixes at 70 F and 700 micro strains Figure 33: Number of cycles to failure for Northern mixes at 70 F and 400 micro strains

10 1 Chapter 1: Introduction Warm mix asphalt (WMA) is becoming popular for its reduced mixing and compaction temperatures which lead to less production cost than hot mix asphalt (HMA). Usually WMA has 50 F lower mixing temperature than HMA which will help to reduce fuel cost to heat the aggregate. It is also noticed that WMA has good workability at lower temperatures since the additives make binder less viscous at lower temperature than HMA mixtures. Lower temperature helps in many ways to the environment as well as for human being such as workers health benefits because of reduced fumes, reduced dust and reduced fuel emissions. Using recycled asphalt pavement (RAP) represents another way to reduce cost and help to make environment friendly pavements. In this study both WMA and RAP were used together. If this combination becomes successful in the field, the pavement industry would help the environment and the work force while reducing the cost. 1.1 Objective Purpose of this study is to evaluate WMA mixtures properties compare to HMA with and without RAP. For that purpose four different WMA technologies were selected; zeolite foaming process (Advera), chemical process (Evotherm 3G), Organic additive (SonneWarmix wax), and Water foaming (laboratory-simulated plant foaming). To evaluate the effect of RAP; 0 and 15 percent RAP binder ratios were used. All mixtures were designed according to NDOT Hveem design procedure and their performance properties were evaluated. Resistance to moisture damage is the first property to evaluate as part of the design procedure. Other properties to be evaluated include; dynamic

11 2 modulus at 0 and 1 freeze thaw cycles, resistance to rutting and resistance to fatigue cracking. This study was completed on two stages, first stage was done by Morgan et al (1), and after the second stage was completed by the author of this Thesis. This Thesis presents the combined results from both stages.

12 3 Chapter 2: Warm mix technologies Currently, several WMA technologies are available; additives blended into binder, additives added to the mixture and foamed asphalt (2). Warm-mix asphalt technologies allow the producers of asphalt mixtures to lower the temperatures at which the material is mixed and placed on the road. Temperature reductions of 50 to 100 F have been reported (3). Temperature reductions have the obvious benefits of reducing fuel consumption and decreasing the production of greenhouse gases which come from the burning of fuels. In addition, engineering benefits include better compaction on the road, the ability to haul the asphalt mix for longer distances, this is because rate of cooling down is lower for WMA than HMA which has higher temperature, and it is possible to extend the paving season since WMA can be paved at lower temperatures (3). Ambarish et al (4) evaluated WMA mixtures and reported that WMA additive such as Evotherm not only reduce short term aging effects on the rheological properties of the binder but also reduces the rate of oxidation which is the cause of long term aging and stiffening of the binder. Zahi et al (5) found that the combination of modified asphalt binder, hydrated lime and WMA technology performed better than the untreated or liquid treated mixtures containing the same modified binder. 2.1 Advera There are two different types of Advera additives available; one is made of Aluminosilicate and the other one is Zeolite powder (6). For this study, hydrated zeolite powder was used which holds 20 % moisture structurally and chemically bound in the zeolite. The zeolite releases moisture and produces micro foaming which remains after

13 4 mixing to help compaction. Advera is added to the aggregate just before mixing the binder. In this study Advera was added at a rate of 0.25% by total weight of mix (6). 2.2 Evotherm Evotherm 3G is a chemical which is in liquid form at room temperature. Evotherm dosage is recommended by the manufacture of the polymer modified asphalt binder from 0.3 to 0.75% by weight of binder. In this study, Evotherm was added to the binder at a rate of 0.6% by weight of binder. If RAP is added to the mix, the Evotherm percentage is measured based on the total weight of the binder in the mix. Evotherm is added to the virgin binder at the recommended heating temperature of 135 C (7). 2.3 SonneWarmix SonneWarmix wax is an organic additive which is in solid form at room temperature. Typical dosage of SonneWarmix is recommended as 0.5 to 1.5% by weight of binder (8). In this study, 1.0% by weight of virgin binder was used. When the RAP is added to the mix the SonneWarmix dosage was calculated according to total weight of binder and added to the virgin binder. 2.4 Water Foaming A laboratory-simulated plant foaming process was used to achieve water foaming of the asphalt binder. In this procedure it is necessary to heat the binder to elevated temperature to enhance foaming. Water is injected at the rate of 3% by the binder weight to the hot binder to create the foamed binder.

14 5 2.5 Warm Mix Asphalt with RAP Fereidoon et al (9) evaluated WMA with different percentages of RAP and concluded that the increase of RAP content produced a stable mix as identified by Marshall Stability and performed well in rutting resistance. However they recommended to use less than 50 % RAP since more than 50 % RAP led to lower tensile strength ratio (TSR) value which indicated moisture damage. Marisa et al (10) evaluated WMA with RAP and emulsion. The RAP was heated up to 140 C and mixed with emulsion at ambient temperature. That WMA mixture was performed better than HMA in terms of moisture sensitivity and rutting resistance. Naisheng et al (11) evaluated RAP with WMA Evotherm and reported that the WMA with RAP combination performed better in dynamic stability and rutting resistance than WMA without RAP. However, the WMA with RAP showed a reduction in TSR value with increase in freeze-thaw cycles, significant reduction in fatigue resistance, and reduced low temperature cracking resistance compared to WMA without RAP. According to the National Asphalt Pavement Association (NAPA), 71.9 million tons of RAP used in the United States in 2014 which is about 28 % increased from 2009 with cost savings of $2.8 billion (12). In 2014, 114 million tons of WMA were produced in the United States which is 7 % increased from 2013 and 577 % increase since 2009 (12). It is clear that the combination of WMA and RAP leads to reduced cost of asphalt pavements and help to reduce environmental pollutions.

15 6 Chapter 3: Material Sources 3.1 Aggregate Sources For this evaluation, four different aggregate sources were selected in collaboration with NDOT material division; two of them from Northern Nevada and two from Southern Nevada. The two Northern Nevada sources are: Spanish Springs (Rocky Ridge: Contract Number 3446; Project Number NH-395-1(023) on US 395; from 1.2 miles south of Waterloo Lane to the junction with US 50 in Carson City) and Lockwood (with Wadsworth Sand: Contract Number 3389; Project Number ARRA-580-1(029), I-580 at Meadowood Mall Way). The two Southern Nevada sources are: North Tenaya (Contract Number 3409; Project Number NH-095-2(051) on US 95; from 0.16 miles north of West Washington Avenue to Ann Road and Package 1; on US 95 at Durango Drive) and Lone Mountain (with Rinker Sand, Contract Number 3421; Project Number STP-095-2(050). US 95 at Summerlin Parkway). All aggregates were lime marinated as per NDOT requirements. According to NDOT standards; 1.5 % of lime used by dry weight of aggregate and marinated for 48 hours. 3.2 Asphalt Binders This study evaluated two different binders supplied by Paramount Petroleum. For Southern mixtures, a PG76-22NV binder was used and for Northern Nevada mixtures, a

16 7 PG64-28NV binder was used. Both binders are polymer modified to overcome the extreme climate changes in Nevada. 3.3 RAP Three different sources of RAP from Nevada were used. Extractions were performed on the RAP material in accordance with AASHTO T164 (13) to determine the binder content and aggregate gradation. A solvent of 85% toluene and 15% ethanol was used to separate the binder from the aggregate, and the binder was recovered from the solvent in a rotary evaporator according to AASHTO 319 (14). Table 1 summarizes the binder contents and binder grades of the RAP materials used in this research effort. The same RAP material from Northern Nevada was used for both aggregate sources of Lockwood and Spanish Springs. Two different RAP sources from Southern Nevada were used with the Southern Nevada aggregate sources.

17 8 Chapter 4: Experimental Plan Mixtures evaluated in this study are presented in Table2 and a list of all of the tests to be performed beyond the mix design are presented in Table 3. The asphalt binder was graded using the superpave Performance Grade (PG) system and additional tests were done as per NDOT requirements. The mix designs were conducted using the NDOT Hveem mix design method. The resistance to moisture damage was evaluated by the indirect tensile strength test at 0 and 1 freeze-thaw cycles, and also by evaluating the dynamic modulus at 0 and 1 freeze thaw cycles. Rutting resistance was measured by the flow number test. Fatigue performance was evaluated in the flexural beam fatigue test. 4.1 Superpave PG System The Superpave PG system is the most recent Asphalt Binder Specification to select the appropriate binder grade for pavements in different climatic regions to ensure good long term performance against rutting, fatigue cracking, and low temperature cracking. The Superpave PG system is mainly based on the climatic conditions at the project locations. The PG notation is PG HH-LL where HH indicates the average seven day maximum pavement design temperature while LL is the minimum pavement design temperature (15). The PG System measures the rheological properties of the binder at the various stages of binder conditions such as service temperatures and binder aging throughout the expected life of the pavement. Currently, all U.S. states use the Superpave PG system (15).

18 9 The high PG grade expresses the maximum temperature at which the asphalt mixture should be resistant to rutting. The high PG grade is checked using the dynamic shear rheometer (DSR) which evaluates the viscous & elastic properties with change of temperature and gives output as Complex Shear Modulus (G*) and Phase Angle (δ) (16). A 1mm thick sample of binder is sandwiched between two 25 mm diameter metal plates, a fixed bottom plate and an oscillating top plate (16). The sample is exposed to a shear stress at a frequency of 10 radians per second, or 1.59 Hz, to simulate truck loading at mph (1). Asphalt binder is a viscoelastic material, and therefore exhibits both viscous properties and elastic properties. The complex shear modulus (G*) indicates the resistance of the binder to deformation when repeatedly sheared, and consists of two components: the elastic modulus, G, and the viscous modulus, G. The phase angle, δ, indicates the time lag between the applied stress and the corresponding strain. A binder with a phase angle equal to 0 is a pure elastic material, since stress and strain occurs simultaneously. A phase angle of 90 signifies a pure viscous material, due to a long delay between applied stress and corresponding strain. A binder s high temperature grade is based on the calculation of G*/sin (δ). For a fresh binder, the G*/sin (δ) value should be over 1.00 kpa (17). For a short term aged binder, or a binder aged in the rolling thin film oven (RTFO), the G*/sin (δ) should be above 2.20 kpa (17). When the value drops below either limits at agiven high temperature PG, the binder is not reliable against rutting at that high temperature and is therefore graded one PG grade lower. The medium PG grade is the temperature which governs the binder resistance to fatigue cracking. This is also checked using the DSR. However, for this test the plates are 8 mm in diameter, and the sample is 2 mm thick. This is to reduce the shear stress acting

19 10 against the machine at lower temperatures and after long term aging which makes stiffer binder. Samples are aged in both the RTFO to simulate short-term aging, and the pressure aging vessel (PAV) to simulate long term aging, as fatigue is a distress that occurs later on in pavement life. In this case, the failure calculation is G*sin (δ). A value below 5000 kpa is required to meet the specification (17). Finally, the low PG grade is determined to ensure sufficient resistance to thermal cracking at the low pavement temperature. This is checked using the bending beam rheometer (BBR). The BBR tests a sample aged in both the RTFO and the PAV, as thermal cracking occurs in the pavement after few years. The BBR uses the concept of time-temperature superposition. A simply supported beam is subjected to a constant load and the creep stiffness and creep rate are measured. The creep load represent the thermal stresses that build up in a pavement as temperatures decrease. The creep stiffness (S(t)) changes depending on the duration of the load. This change in stiffness with respect to time is known as the m-value. A passing binder has a stiffness below 300 MPa, as well as an m-value above (17). If these criteria are not satisfied at the expected low pavement temperature then the binder will not resist thermal cracking, therefore, graded one PG grade warmer. 4.2 Hveem Mix Design The Nevada department of transportation (NDOT) follows the Hveem mix design method for asphalt mixtures. In this method, the optimum binder content is selected on the basis of optimum air voids and film thickness and minimum stability. An optimum film thickness capable of coating each aggregate particle with the most durable mix is

20 11 required, usually highly absorptive aggregates require more binder to get sufficient film thickness. It requires a stable mix capable of resisting traffic loading. The internal friction between aggregate particles and cohesion created by the asphalt binder generates this stability (18). The NDOT Hveem mix design was conducted for all mixtures following NDOT Type 2 C specification for heavy traffic with 19 mm nominal maximum aggregate size. NDOT requires a minimum Hveem stability of 37 to resist deformation (Nev T303D (19)) for heavy traffic (> 1 million ESALs) and a minimum unconditioned indirect tensile strength (Nev T341D (20)) of 65 psi along with a minimum tensile strength ratio (Nev T341D (20)) of 70%. A binder viscosity range of 0.28±0.03 Pa.s was used to determine the mixing temperatures for HMA using the viscosity temperature susceptibility chart. At this mixing temperature, two replicate specimens at each of four different asphalt binder contents were mixed, short-term conditioned for 16±1 hours at 140 F and then compacted at 230 F using the Hveem kneading compactor. The samples were leveled with a load of 12,600 psi after conditioning for 1.5 hours at 140 F. The leveled specimens were kept in an oven for 3-4 hours at 140 F before testing in the stabilometer. The Hveem stabilometer measures the resistance to deformation of a compacted specimen under increasing vertical load. The stabilometer value ranges from 0 to 90. The stability of liquid and an incompressible solid are 0 and 90, respectively. The stabilometer value is calculated using following equation;

21 12 S = 22.2 [ P hd P v P h ] Where: S = stabilometer value Ph = horizontal pressure, for corresponding Pv D = displacement on specimen and Pv = vertical pressure (typically 2800 kpa (400 psi)) Mixing and compaction temperatures for each WMA additives were determined with the verification of coating and compactability at the optimum binder content of the HMA mix as determined by the Hveem mix design. 4.3 Coating of WMA mixtures It is required to find the mixing temperature for WMA to get proper coating. The aggregate coating was tested following AASHTO T 195 (21). The samples were mixed at optimum binder content and a minimum mixing temperature. The samples were sieved on a 3/8 sieve immediately after mixing and all coarse particles were examined carefully since coating of fine aggregates is not critical as for coarse aggregate. The coating criterion is fulfilled if at least 95% of coarse particles are fully coated. If the coating criterion is not passed, the mixing temperature is increased until 95 % of coarse aggregate in the WMA mixture are coated. This temperature represents the mixing temperature of the WMA mix.

22 Compactability of WMA Mixtures There is no procedure in the Hveem mix design related to WMAs, hence for compactability, AASHTO test R35 (7) was followed which standard is related to the Superpave mix design. The compactability tests for WMA mixtures were done according to AASHTO R35 (7). The compactability of warm mix asphalt mixtures is defined as the ratio of gyrations in the Superpave Gyratory Compactor (SGC) needed to reach 92 percent relative density at 55 F (30 C) below the planned compaction temperature over the SGC gyrations needed to reach same relative density at the planned compaction temperature. The recommended compactability criterion is a gyration ratio of 1.25 or less. Since there is no correlation between Hveem design and Superpave Volumetric design, the samples were compacted at Ndesign of 100 gyrations to represent the traffic level greater than 3 million and less than 30 million ESALs. Sample size measuring mm in height and 150mm diameter. Two samples of each replicates were compacted at proposed compaction temperature and 55 F (30 C) below planned compaction temperature using the SGC. The relative SGC compaction and the compaction ratio are defined in the following equations respectively: Where: %G mmn = relative density at N gyrations; %G mmn = 100 { G mbh d G mm h N } G mb = bulk specific gravity of the specimen compacted to N design gyrations;

23 14 h d = height of the specimen after Ndesign gyrations, from the Superpave gyratory compactor; h N = height of the specimen after N gyrations, from the Superpave gyratory compactor, mm. Where: Gyration ratio = (N 92 ) T 30 (N 92 ) T (N 92 ) T 30 = gyrations needed to reach 92 percent relative density at 30 C below the planned field compaction temperature; (N 92 ) T = gyrations needed to reach 92 percent relative density at the planned field compaction temperature. 4.5 Indirect Tensile Strength The resistance of the mixtures to moisture damage is a critical part of the NDOT Hveem mix design method.the impact of moisture damage was simulated through the freeze-thaw cycling (F-T) process of AASHTO T283 (22). Samples were made in the Hveem compactor and divided in two sets; unconditioned and moisture conditioned. This test involves curing the loose mix samples for 15±3 hours at 140±5 F and then compact in the Hveem compactor to 8±1% air voids at 230±5 F. The number of tamps, foot pressure and leveling load are adjusted to get the desired air voids. The evaluations of moisture susceptibility of mixtures were conducted according to Nev. T341D (20) standard procedure. This test involves the measurement of change in tensile strength from the effects of water saturation and accelerated water conditioning with a freeze-thaw cycle.

24 15 After compaction, the specimens were divided into unconditioned and conditioned subsets. The unconditioned subset involved keeping the specimen in an environmental chamber at 77±1 F until it tested. The conditioned subset was subjected to vacuum saturation of 70-80% followed by freezing at 0 F for 16 hours and then thawing in a 140 F water bath for 24 hours. Finally, the specimens were kept in a 77 F water bath for 2 hours prior to indirect tensile strength testing. The specimens were loaded along their diameter at a rate of 2 inch/min and the peak load at failure is measured and the tensile strength is calculated using the following equation. S t = 2P πtd Where: St = tensile strength, psi P = maximum load, lb D = specimen diameter, inch and t = thickness, inch. The TSR is calculated as a ratio of tensile strength of the conditioned specimens over the unconditioned specimens. NDOT specification requires minimum unconditioned tensile strength at 77 F of 65 psi for PG64-28NV binder and 100 psi for PG76-22NV binder and a minimum TSR of 70%. The addition of lime reduces the moisture damage of the mixtures.

25 Engineering Properties The engineering properties of all mixtures were evaluated in terms of the dynamic modulus E*. To evaluate dynamic modulus properties AASHTO PP60 (23), AASHTO TP79 (24) and AASHTO PP62 (25) were followed. The asphalt mixture was compacted in the SGC into a cylindrical sample having 6 inches diameter and 6.9 inches height. E* test specimen is cored from the center of the SGC sample into a cylinder having 4 inches diameter and 5.9 inches height. An air voids level of 7±0.5 % was targeted for the final cored specimens. The test is conducted at frequencies of: 10, 1, and 0.1 Hz and at temperatures of 40, 68, 113 F for the PG76-22NV mixtures and 40, 68, 104 F for the PG64-28NV mixtures. The testing setup for E* in AMPT machine showed in Figure 1 Figure 1: Testing setup for dynamic modulus in AMPT machine. The measured stress-strain relationship at all combinations of testing temperatures and frequencies are used with volumetric properties to develop the dynamic modulus master curve (25). The master curve is constructed using the principle of time-

26 17 temperature superposition, the data are shifted at various temperatures with respect to time until the curves merge into a single smooth function. Time-temperature superposition is only applicable in the linear vicoelastic region and is only applicable to thermo-rheologically simple materials, which includes bituminous materials (26). A typical master curve is showen in Figure 2 Figure 2: Dynamic Modulus master curve. 4.7 Resistance to Rutting The resistance to rutting was evaluated for all the mixtures using the Flow Number (FN) test. The FN tests were done according to AASHTO PP60 (23) and AASHTO TP79 (24). The FN test consists of subjecting a compacted asphalt mixture specimen at a specified temperature to a repeated haversine axial compressive load pulse of 0.1 second and a rest time of 0.9 second. The asphalt mixture is compacted in the SGC into a cylindrical sample having 6 inches diameter and 6.9 inches height. The FN

27 18 test specimen is cored from the center of the SGC sample into a cylinder having 4 inches diameter and 5.9 inches height. An air voids level of 7±0.5 % was targeted for the FN test specimens. The cumulative permanent deformation is recorded as a function of number of load cycles. The permanent axial strain is calculated as the ratio of the permanent deformation over the gauge length. The cumulative permanent strain can be defined by the primary, secondary, and tertiary zones as showed in Figure 3. In the primary zone, the permanent strain increases rapidly with volume change but at a decreasing rate. In the secondary zone, the permanent strain rate maintains a constant value until it starts to increase in the tertiary creep zone. In the tertiary stage high levels of permanent axial strain associated with plastic or shear deformation under no volume change. This stage is reached when the specimen is beginning to deform significantly and individual aggregates composing the shape of the mixture are moving past each other. The point at which the tertiary stage begins is the flow number. In other words, the FN is defined as the number of load cycles corresponding to the minimum rate of change of permanent axial strain (24).

28 19 Figure 3: Cumulative permanent axial strain with respect to number of cycles in the flow number test The temperature of the FN test is selected to represent an equivalent critical rutting temperature for the location of the project which is a function of the high temperature PG of the asphalt binder. According to AASHTO TP 79 (24), the flow number test should be conducted at the 50% reliability design temperature as determined using the LTPP Bind version 3.1 software when the target rut depth is 12.5 mm and a depth of 20 mm for surface courses, and the top of the pavement layer for intermediate and base courses. The FN tests were conducted for the southern mixtures (PG76-22NV) at 147 F (64 C) and for the northern mixtures (PG64-28NV) at 123 F (50.5 C). All FN tests were conducted under a zero confining pressure and an axial deviator stress of 87 psi.

29 Fatigue Analysis-Flexural beam fatigue test Figure 4: Testing setup for flexural beam test. Fatigue cracking occurs after repeated heavy traffic loading due to bending tensile stress in the asphalt concrete layers. For thin pavements, the crack initiates at the bottom of the asphalt concrete layer and propagates towards the top surface. For thick pavements, top-down crack is most common. This crack occurs due to high tensile stress developed at tire-pavement interface and oxidation of asphalt binder. The resistance of the various mixtures to fatigue cracking was evaluated using the flexural beam fatigue test AASHTO T321 (27). The beam specimen is subjected to a 4-point bending with free rotation and horizontal translation at all load and reaction points, testing setup is shown in Figure 4. This produces a constant bending moment over the center portion of the specimen. In this research, constant strain tests were conducted at a strain levels of 700 and 400 microns using a repeated haversine load at a frequency of 10 Hz, and a test

30 21 temperature of 70 F (21.1 C) using a pneumatic testing system. The initial flexural stiffness is measured at the 50th load cycle. Fatigue life or failure is defined as the number of cycles corresponding to a 50% reduction in the initial stiffness, In Figure 5 flexural stiffness ratio is illustrated. Stiffness was calculated using following equations (28). All beam specimens were long term oven aged according to AASHTO R30 (29) for 5 days at 185 F. The flexural stress, strain, and stiffness of the beam fatigue are calculated in the following equations, respectively. σ t = 3ap bh 2 Where: σt = maximum tensile stress, psi a = center to center spacing between clamps, inch P = load applied by actuator, lb b = average specimen width and, inch h = average specimen height, inch. Ɛ t = 12δh (3L 2 ) (4a 2 ) Where: Ɛt = maximum tensile strain, inch/inch δ = maximum deflection at center of beam, inch

31 22 h = average specimen height, inch L = length of beam between outside clamps, inch and a = space between inside clamps, L/3, inch. S = σ t Ɛ t Where: S = flexural beam stiffness, psi σt = maximum tensile stress, psi and Ɛt = maximum tensile strain, inch/inch. Figure 5: Typical curve for flexural stiffness ratio.

32 23 Chapter 5: Test Results and Analysis The purpose of this part of the study is to characterize the asphalt binder and RAP materials and to evaluate and compare the performance characteristics of all HMA and WMA mixtures from the southern and northern Nevada aggregate sources. The evaluated performance characteristics included; engineering property, resistance to moisture damage, resistance to rutting and resistance to fatigue cracking. 5.1 Binder Characterization Both binders PG76-22NV and PG64-28NV were tested as per NDOT requirements according to AASHTO and NDOT standards, the properties are shown in Table 4 and Table 5. The mixing and compaction temperatures for the PG76-22NV HMA mixtures were provided by the supplier as 350 F and 300 F, respectively. The mixing and compaction temperatures for the PG64-28NV HMA mixtures were provided by the supplier as 320 F and 300 F, respectively. All HMA samples for mix design were mixed at these temperatures and compacted at 230 F, and all HMA samples for performance related tests were mixed and compacted at these recommended temperatures. 5.2 RAP Characterization It is necessary to know the RAP aggregate gradation to do the designs. AASHTO M323 (30), recommends to select a virgin binder one grade softer than required if the RAP percentage is from 15 to 25. However, it was decided to use the same binder grade for all RAP percentages to evaluate the impact of fixed binder grade on mixtures with multiple RAP contents. Solvent extractions were performed on the RAP materials in accordance with AASHTO T164 (13). A solvent of 85% toluene and 15% ethanol was

33 24 used to separate the binder from the aggregate, and the binder was recovered from the solvent in a rotary evaporator. Superpave PG grading was performed on the RAP binders and results are shown in Table Mix Design Details Aggregate gradations were established to meet NDOT type 2C specification and NDOT Hveem mix design was followed for all the mixtures. Even though compaction temperatures were determined by the supplier based on viscosity-temperature relationship, the NDOT Hveem mix design compacts all mixtures at 230 F using the California Kneading Compactor. NDOT requires a minimum Hveem stability of 37 to resist deformation (Nev T303D (19)) for heavy traffic and a minimum unconditioned tensile strength (Nev T341D (20)) of 65 psi at 77 F for PG64-28NV mixtures and 100 psi at 77 F for PG76-22NV mixtures along with a minimum tensile strength ratio (Nev T341D (20)) of 70%. All HMA and WMA mixtures satisfied these standards. It should be noted that all HMA and WMA mixtures included 1.5 % hydrated lime as per NDOT specifications. Aggregate gradation details are given in Table 6 to Table 9. Design details for all mixtures are illustrated in Table 10 to Table Engineering Properties The following abbreviations are used in the graphical presentations of the data: - LM: Lone Mountain - NT: North Tenaya - SS: Spanish Springs - LW: Lockwood

34 25 - HMA: Hot Mix Asphalt - ADV: Advera - EVO: Evotherm - SON: SonneWarmix - FOAM: Water Foaming - 0: 0% RAP binder ratio - 15: 15% RAP binder ratio Resistance to Moisture Damage: Tensile Strength It should be noted that NDOT mandates the use of hydrated lime to improve the resistance of asphalt mixtures to moisture damage. The tensile property of an asphalt mixture is provided through the combination of bond between the asphalt binder and aggregates and tensile characteristics of the asphalt binder. Moisture damage typically affects both of these properties and leads to a reduced tensile strength property of the asphalt mixture. This research evaluated the impact of WMA additives and RAP on the tensile strength properties of asphalt mixtures at the un-conditioned and moisturedamaged stages. Figure 6 and Figure 7 present the tensile strength properties of the northern and southern mixtures at the un-conditioned stage (0 F-T) and after moisturedamage (1 F-T). The whiskers on the bars in Figure 6 and Figure 7 represent the 95% confidence interval of the measured values. Overlapping confidence intervals indicates that the compacted mixtures have statistically similar properties. Figure 8 and Figure 9 present the tensile strength ratio as the ratio of moisture-damaged tensile strength over the un-conditioned tensile strength. Confidence interval is calculated using the following equation.

35 26 CI = Z α/2σ n CI = confidence interval, Zα/2 = confidence coefficient, 1.96 for 95 % confidence interval, σ = standard deviation, and n = sample size In Lone Mountain Mixtures, the un-conditioned tensile strength properties of all mixtures are above the NDOT minimum requirement of 100 psi at 77 F, the addition of 15% RAP binder ratio increased both the un-conditioned and moisture-damaged tensile strength property of all mixtures, the WMA Evotherm and SonneWarmix mixtures exhibited tensile strength properties similar to the HMA mix, the WMA Advera showed tensile strength properties lower than the HMA mix with 0% RAP and only lower moisture-damaged tensile strength properties with 15%RAP. The tensile strength ratios of all mixtures are above the NDOT minimum requirement of 70%. North Tenaya mixtures also satisfied NDOT minimum requirement of 100 psi at 77 F for un-conditioned tensile strength properties. The addition of 15 % RAP binder ratio slightly reduced the tensile strength properties of the HMA mixture while it slightly increased the tensile strength properties of the WMA mixtures. The WMA mixtures exhibited tensile strength properties lower than HMA mixture with 0% RAP while their tensile strength properties were similar to HMA mixture with 15% RAP. The tensile strength ratios of all mixtures are above the NDOT minimum requirement of 70%. For north mixtures the minimum requirement for un-conditioned tensile strength is 65 psi at 77 F. In Spanish Springs mixtures the un-conditioned tensile strength

36 27 properties of all mixtures are above the NDOT minimum requirement of 65 psi at 77 F. The addition of 15 % RAP binder ratio increased the tensile strength of all mixtures. The WMA Advera, Evotherm, and Foam mixtures exhibited tensile strength properties similar to the HMA mix. The WMA SonneWarmix showed tensile strength properties similar to the HMA mix with 0% RAP and lower tensile strength properties with 15% RAP. The tensile strength ratios of all mixtures are above the NDOT minimum requirement of 70%. When Lockwood mixtures are considered, the un-conditioned tensile strength properties of all mixtures are above the NDOT minimum requirement of 65 psi at 77 F. The addition of 15 % RAP binder ratio increased the tensile strength properties of the HMA mix and the WMA Advera and SonneWarmix mixtures but did not significantly impact the tensile strength properties of the WMA Evotherm and Foam mixtures. The WMA Advera and Evotherm mixtures exhibited tensile strength properties higher than the HMA mixture with 0 and 15% RAP. The WMA SonneWarmix mixture exhibited tensile strength properties lower than the HMA mixture with 0% RAP and tensile strength properties similar to HMA mixture with 15% RAP. The WMA Foam mixture exhibits tensile strength properties higher than the HMA mixture with 0% RAP and tensile strength properties similar to HMA mixture with 15% RAP. The tensile strength ratios of all mixtures are above the NDOT minimum requirement of 70%. In summary, all HMA and WMA mixtures met NDOT specifications on minimum un-conditioned tensile strength property and tensile strength ratio. In most cases the addition of 15% RAP increased the tensile strength properties of HMA and WMA mixtures. Most of the WMA Evotherm mixtures exhibited tensile strength properties similar to HMA mixtures with both southern and northern aggregate sources.

37 28 The impact of the Advera and SonneWarmix on tensile strength properties depended on the aggregate source and the presence of RAP. The Foam mixtures exhibited tensile strength properties similar to HMA mixtures with the northern aggregate source except Lockwood mixtures with 0% RAP. Overall, WMA additives did not significantly impact the tensile strength properties of the mixture Engineering Property: Dynamic Modulus The E* is a fundamental engineering property of the asphalt mixture. It is provided through the combination of bond between asphalt binder and aggregates, tensile characteristics of the asphalt binder, physical and engineering properties of the aggregates, and aggregate gradation. Moisture damage attacks the properties and leads to a reduced E* property of the asphalt mixture. This research evaluated the impact of WMA additives and RAP on the E* properties of asphalt mixtures at the un-damaged and moisture-damaged stages. Using the viscoelastic behavior of the asphalt mixture the master curve is developed and can be used to evaluate E* at any combination of pavement temperature and traffic speed. For the purpose of comparative analyses, the E* values at 68 F and 10Hz were selected since the 68 F represents an average pavement temperature and the 10 Hz represents the loading rate of a truck traveling at 60 mph. Typically, an E* property at 68 F and 10Hz above 400 ksi represents a good asphalt mixture that is stable enough to resist rutting with sufficient flexibility to resist cracking. On the other an asphalt mix with an E* at 68 F and 10Hz above 1,000 ksi may be too stiff to resist cracking.

38 29 Measured dynamic modulus (E*) values at 68 F and 10 Hz for 0 and 1 Freeze thaw cycles are shown in Figure 10 and Figure 11. The whiskers on the bars in Figure 10 and Figure 11 represent the 95% confidence interval of the measured values. Overlap in the confidence intervals indicates statistically similar values. Dynamic modulus master curves are presented in Figure 12 to Figure 27. The un-damaged and moisture-damaged E* properties of the Lone Mountain mixtures are increased when RAP is added. The un-damaged E* is not significantly affected by the WMA additives for mixtures with 0 and 15% RAP binder ratios. The moisture-damaged E* property of the WMA mixtures with 0% RAP binder ratio are significantly lower than the E* property of the HMA mix. The moisture-damaged E* property of the WMA mixtures with 15% RAP binder ratio are similar to the E* property of the HMA mix. The addition of 15% RAP binder ratio to the North Tenaya Mixtures slightly increased the E* property of all mixtures. The un-damaged and moisture-damaged E* properties of the WMA mixtures with 0 and 15% RAP binder ratios are differ from the E* property of the HMA mix. WMA mixtures without RAP lower E* except for Advera un-damaged. The un-damaged and moisture-damaged E* properties are not significantly affected by the WMA additives for mixtures with 0 and 15% RAP binder ratios. The addition of 15% RAP binder ratio to the Spanish Springs mixtures increased the E* property of all mixtures. The un-damaged and moisture-damaged E* properties of the WMA mixtures with 0% RAP binder ratio are significantly lower than the E* properties of the HMA mix. The Advera mixture exhibited higher E* properties than the other WMA mixtures with both 0% and 15% RAP binder ratios.

39 30 Lockwood Mixtures showed increased in E* with the addition of 15 % RAP binder ratio in all mixtures. The un-damaged and moisture-damaged E* properties of the WMA mixtures with 0% RAP binder ratio are slightly lower than the E* values of the HMA mix. The un-damaged and moisture-damaged E* properties of the WMA mixtures with 15% RAP binder ratio are significantly lower than the E* properties of the HMA mix. The un-damaged and moisture-damaged E* properties are not significantly affected by the WMA additives for mixtures with 0 and 15% RAP binder ratios. In summary, all WMA and HMA mixtures exhibited an increase in the E* properties when RAP is added at 15% binder ratio. In most cases, the type of WMA addtives did not significantly impact the E* property for all mixtures Resitance to Rutting: Flow Number The higher the Flow number (FN) value the higher the resistance of the asphalt mixture to rutting. Figure 28 and Figure 29 present the FN values for the southern and northern mixtures, respectively. The addition of 15% RAP binder ratio moderately increased the FN values for all Lone Mountain mixtures. The WMA Advera mix exhibited similar FN values to the HMA mix with 0 and 15% RAP binder ratios. The WMA Evotherm mix exhibited lower FN value than the HMA at the 0% RAP binder ratio and similar FN value to the HMA mix at the 15% RAP binder ratio. The WMA SonneWarmix mix exhibited the lowest FN values with the 0 and 15% RAP binder ratios. The addition of 15% RAP binder ratio to the North Tenaya mixtures significantly increased the FN values for all mixtures. All WMA mixtures exhibited similar FN values to the HMA mix at the 0% RAP binder ratio. All WMA mixtures exhibited lower FN

40 31 values than the HMA mix at the 15% RAP binder ratio. The type of WMA additive did not impact the FN values of mixtures at the 0% RAP binder ratio. The type of WMA additive had a significant impact on the FN values at the 15% RAP binder ratio, where the Advera mix showed the highest FN followed by Evotherm while the SonneWarmix exhibited the lowest FN value. The addition of 15% RAP binder ratio to the Spanish Springs mixtures moderately increased the FN value of the HMA mix but did not impact the FN values of WMA mixtures, except for the WMA SonneWarmix. All WMA mixtures exhibited lower FN values than the HMA mixtures at the 0% and 15% RAP binder ratios. The type of WMA additive had a moderate impact on the FN values of mixtures with 0% RAP binder ratio but no impact with 15% RAP binder ratio, except the WMA Foam mix. The WMA Foam mix exhibited similar FN values at the 0% and 15% RAP binder ratios. The addition of 15% RAP binder ratio to the Lockwood Mixtures significantly increased the FN value of the HMA mix and moderately increased the FN values of the WMA mixtures, except the WMA Foam mix which did not show an impact. The type of WMA additive did not impact the FN values of mixtures with both 0% and 15% RAP binder ratios, except the WMA Foam mix. The WMA Advera, Evotherm, and SonneWarmix mixtures exhibited lower FN values than the HMA mixtures at the 0% and 15% RAP binder ratios. The WMA Foam mix exhibited FN values that are similar to HMA at the 0% RAP binder ratio but significantly lower at the 15% RAP binder ratio. Overall, WMA SonneWarmix exhibited lowest Flow Numbers in most of the southern and northern mixtures. According to AASHTO TP79 (24) if the FN is greater than 190 for HMA and 105 for WMA; those mixtures can be used for traffic level of 10

41 32 million to 30 million ESALs. Except for the North Teneya mixtures with no RAP all other mixtures can be used under this traffic level. If the traffic is more than 30 million, HMA requires 740 and WMA needed 415, only few mixtures can be used under this traffic level such as HMA LW 15RAP, WMA FOAM LW 0RAP and 15RAP and WMA EVO LW 15 RAP. When the traffic level is 3 to 10 million, FN of 50 in HMA and 30 in WMA is required; hence all the mixtures can be used under this traffic level Resistance to Fatigue: Flexural Beam Fatigue resistance data presented in Figure 30 to Figure 33 showing number of cycles to failure at 70 F at flexural strain levels of 700 and 400 microns applied. The 70 F testing temperature is a representative fatigue cracking temperature for the state of Nevada while the 700 and 400 microns level represent the range of tensile strains at the bottom of typical asphalt concrete layer under heavy truck load. The addition of 15% RAP binder ratio to the Lone Mountain Mixtures did not impact the fatigue resistance of the HMA mix and moderately reduced the fatigue resistance of the WMA mixtures at the 700 microns. At 400 microns all the mixtures showed lower resistance to fatigue when RAP is added except the WMA Advera mix. The type of WMA additive did not impact the fatigue resistance of the mixture at both the 0% and 15% RAP binder ratios at 700 microns. At 400 microns the WMA Evotherm mix showed significant reduction in fatigue resistance when RAP is added at 15 % binder ratio. The WMA mixtures showed higher fatigue resistance than the HMA mixture at the 0% RAP binder ratio and similar fatigue resistance to the HMA mixture at the 15% RAP binder ratio at 700 microns. At 400 microns the WMA Advera and Evotherm mixtures