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31 Mixture Volumetrics Appendix E provides detailed volumetric properties by field project with a comparison of mixture types for each field proj- ect and a separate comparison of specimen types for each field project. Volumetrics provided include total AV for each group of specimens in terms of the average and range, theoretical maxi- mum mixture specific gravity (Gmm), percent binder absorp- tion (Pba), and effective binder film thickness (FT) defined as the effective binder content (Pbe) coating the surface area of the aggregates with parameters calculated by Saskatchewan Highways and Transportation method STP 204-19. Gmm values were measured for LMLC specimens according to AASHTO T 209 and taken from mix design information for onsite PMLC specimens and PMFC cores. The d2s value of 0.014 for single- operator, single-laboratory provided in AASHTO T 209 was used in the comparisons of mixture type (WMA versus HMA) and in the comparisons of specimen type (PMFC cores at con- struction versus LMLC specimens and versus offsite PMLC specimens) because the other volumetric parameters (i.e., Pba and effective binder FT) were calculated from Gmm. Higher Gmm values corresponded to higher Pba values and lower effective binder FT values. The results of these comparisons can be summarized as follows: ⢠For most mixtures from the four field projects, volumetrics for WMA and HMA were not different for each specimen type based on d2s values. The only exceptions were lower Gmm values for both Iowa WMAs with RAP for LMLC speci- mens and for WMA foaming from the Texas field project for both onsite and offsite PMLC specimens and higher Gmm values for two Montana WMAs for offsite PMLC specimens. ⢠For most Texas, Montana, and New Mexico mixtures, vol- umetrics for PMFC cores at construction and laboratory mixtures (LMLC and offsite PMLC specimens) were not dif- ferent for each mixture type based on d2s values. The only exceptions were lower Gmm values for offsite PMLC speci- mens for WMA foaming with RAP from the New Mexico field project and higher Gmm values for LMLC specimens for HMA from the Texas field project. For the Iowa mixtures, volumetrics for PMFC cores at construction were not dif- ferent from those for offsite PMLC specimens, but LMLC specimens had higher Gmm values. As part of the WMA laboratory-conditioning experiment, volumetrics of LMLC specimens and onsite PMLC specimens were also calculated and compared in terms of binder absorp- tion and film thickness (STP 204-19) to further examine factors that may influence moisture susceptibility. This com- parison indicated that all onsite PMLC specimens (except for WMA foaming from the Texas field project) had higher Gmm values and Pba and lower effective binder FT. Thus, the loose plant mix experienced more conditioning/binder absorption prior to compaction than that mixed in the laboratory. The reduction in mixing and compaction temperatures (Tm and Tc, respectively) and the incorporation of WMA additives resulted in lower Gmm values and lower binder absorption as compared with HMA. This phenomenon could reduce the adhesive bond strength between aggregates and binder, pos- sibly making WMA more moisture susceptible in the early life of the pavement. WMA Laboratory Conditioning The objective of the WMA laboratory-conditioning exper- iment was to propose standard laboratory-conditioning pro tocols for WMA specimens for moisture-susceptibility performance testing. These protocols are intended to be used as part of the WMA mix design procedure or the QA program for WMA. Different conditioning protocols were selected for fabricating WMA LMLC and PMLC specimens, and these specimens were tested to determine the effect of the condi- tioning protocol on the mixtureâs dry MR stiffness. PMFC C H A P T E R 3 Findings and Applications
32 This same conditioning protocol of 2 h at Tc provided the best agreement between MR stiffnesses for LMLC specimens and corresponding PMFC cores for the WMA mixtures from both the Iowa and Texas field projects with only lower MR stiffnesses for the LMLC specimens for WMA Evotherm® 3G with RAP from Iowa and the least difference between these specimen types for WMA foaming from Texas. The condi- tioning protocols at longer times or higher temperatures resulted in LMLC specimens of more mixtures per field proj- ect with MR values that were statistically higher than PMFC cores at construction. In summary, dry MR stiffness results showed that the stiff- nesses of LMLC specimens increased with higher condition- ing temperatures and longer conditioning time and that WMA was more sensitive to conditioning temperature than conditioning time. Among the five selected conditioning pro- tocols for LMLC specimens, 2 h at Tc was most representative in terms of stiffnesses for both HMA and WMA pavements in their early life. Considering the difficulty in accurately defin- ing Tc in the field, the common range of Tc for HMA and WMA (Table for this project) and the current standard tem- perature for HMA in AASHTO R 30 of 2 h at 275°F (135°C) and 240°F (116°C) instead of 2 h at Tc was proposed as the standard laboratory-conditioning protocol prior to compac- tion for HMA and WMA LMLC specimens, respectively. Table 3-2 summarizes the corresponding results for both onsite and offsite PMLC specimens, including statistical anal- ysis by Tukeyâs HSD test at a 5% significance level to compare the different conditioning protocols with colored shading as described previously. Based on the ANOVA results, the inter- action effect between conditioning protocol and orientation was again statistically insignificant for all mixtures. The main effect orientation was statistically insignificant for all mix- tures except for Texas WMA Evotherm DATâ¢, but the differ- ence was practically insignificant. The effect of conditioning protocol was statistically significant for all mixtures. cores at construction and after a winter in service were also incorporated in the experimental design to represent HMA and WMA pavements in their early life. In addition to the primary parameter used in this experiment (i.e., dry MR stiff- ness), mixture compactability in terms of N to 7% AV was also compared. A small experiment was also completed to evaluate the effects of binder stiffness, aggregate orientation, and AV on MR stiffness among the different specimen types. Appendix A provides detailed results for HMA and WMA comparing LMLC and PMLC specimens to PMFC cores dur- ing the early life of the pavement. Summary results for dry MR stiffness are presented in this section in addition to brief conclusions from the comparison of other parameters and the small experiment. Table 3-1 summarizes the results for LMLC specimens, including statistical analysis by Tukeyâs HSD test at a 5% sig- nificance level, to compare the different conditioning protocols. Prior to examining this main factor of interest, neither the effect of orientation (i.e., rotating the specimen 90 degrees after the first measurement, as required by the standard method) nor the interaction effect between orientation and conditioning proto- col was shown to be statistically significant by a split plot design analysis. The effect of conditioning protocol was statistically significant for all mixtures, except for Texas HMA. In Table 3-1, red shading indicates statistically higher MR stiffness values for LMLC specimens as compared with PMFC cores at construction, green shading indicates statistically equivalent performance for these specimen comparisons, and yellow shading indicates that LMLC specimens exhibited statistically lower MR stiffness values for the same compari- son. As shown, all of the conditioning protocols resulted in HMA LMLC specimens with MR stiffnesses that were statisti- cally equivalent as compared with PMFC cores for the Texas field project, but only the 2 h at Tc protocol provided the same results for the Iowa field project, with all other protocols result- ing in higher MR stiffnesses for the HMA LMLC specimens. Location Mixture Type LMLC Conditioning Protocols 2 h @ Tc 4 h @ Tc 2 + 16 + 2 h @ Tc 2 h @ 275°F 4 h @ 275°F Iowa HMA+RAP Evotherm 3G+RAP Sasobit+RAP Texas HMA N/A Evotherm DAT Foaming Least Difference Key LMLC = PMFC LMLC > PMFC LMLC < PMFC Note: Tc: compaction temperature. Table 3-1. Summary trends for WMA laboratory-conditioning experiment for dry MR stiffness of LMLC specimens vs. PMFC cores at construction.
33 For all Texas mixtures, onsite PMLC specimens exhibited equivalent MR stiffnesses to those for PMFC cores at con- struction. For the Iowa mixtures, this same equivalence was only valid for Iowa WMA Evotherm® 3G with RAP, but the least difference as compared to PMFC cores at construction was shown for onsite PMLC specimens for the other two Iowa mixtures. Generally, conditioning protocols for offsite PMLC specimens yielded statistically higher MR stiffnesses as com- pared with those for PMFC cores at construction. Therefore, stabilizing the plant mix to a standard Tc of 240°F (116°C) and 275°F (135°C) for WMA and HMA, respectively, to pre- pare onsite PMLC specimens is proposed for QA. If onsite PMLC specimens are not available, reheating plant mix to a standard Tc of 240°F (116°C) and 275°F (135°C) is proposed to produce offsite PMLC specimens for WMA with additives and HMA, respectively. Considering the evaporation of water in foamed mixtures and the assumed loss of effectiveness of foaming properties when reheating, conditioning of offsite PMLC specimens for WMA foaming must follow the same protocol as that for HMA, i.e., reheating to 275°F (135°C). Compaction temperatures for WMA from the Montana field project were significantly higher than those from the Iowa and Texas field projects (Table 3-2). Therefore, to fur- ther validate the proposed conditioning protocols for offsite PMLC specimens, offsite PMLC specimens for the Montana field project were fabricated following the proposed proto- col as well as reheating to the actual Tc of 315°F (157°C) for HMA and 275°F (135°C) for WMA with additives. Then, the MR stiffness of these offsite PMLC specimens and cor- responding onsite PMLC specimens were compared against PMFC cores at construction. MR stiffness results and results from the same type of statistical analysis used for LMLC and PMLC specimens from the Iowa and Texas field projects are provided in Appendix A. The summary comparisons shown in Table 3-2 also include the results from Montana. As shown, for Montana HMA and WMA Evotherm® 3G, both the proposed conditioning proto- cols and those of reheating to actual Tc yielded offsite PMLC specimens with equivalent MR stiffnesses to the PMFC cores at construction. In the case of Montana Sasobit®, higher MR stiff- nesses were shown for both sets of offsite PMLC specimens; however, a smaller difference in MR stiffness was shown using the proposed conditioning protocol. Therefore, the proposed alternative conditioning protocol for offsite PMLC specimens of reheating plant mix to 275°F (135°C) for HMA and WMA foaming and to 240°F (116°C) for all WMA mixtures except WMA foaming was verified. In addition to the primary parameter of interest in this experiment (i.e., dry MR stiffness), mixture compactability was compared for specimens fabricated with different con- ditioning protocols. Mixture compactability data in terms of the number of SGC gyrations (N) to 7% AV agreed with the dry MR stiffness results. More gyrations were required to achieve the same AV level during compaction for LMLC specimens conditioned with protocols with longer times and at higher temperatures. Onsite PMLC specimens and PMFC cores taken at con- struction were expected to have similar dry MR stiffnesses, Location Mixture Type Conditioning Protocols Onsite PMLC Offsite PMLC 1-2 h @ Tc R to Tc R + 2 h @ Tc 16 h + R + 2 h @ Tc R + 4 h @ 275°F Iowa HMA+RAP Least Difference Evotherm 3G+RAP Sasobit+RAP Least Difference Texas HMA Evotherm DAT Foaming Onsite PMLC Offsite PMLC 1-2 h @ Tc R to 275°F (HMA) R to 240°F (WMA) Reheat to Tc Montana HMA Evotherm 3G Sasobit Least Difference Key PMLC = PMFC PMLC > PMFC Note: R: reheat; Tc: compaction temperature. Table 3-2. Summary trends for WMA laboratory-conditioning for dry MR stiffness of PMLC specimens vs. PMFC cores at construction.
34 trends observed for the different performance parameters measured in laboratory tests. The comparisons in test results shown in these summary tables are based on the following for each test parameter: ⢠Wet IDT strength: ANOVA and Tukeyâs HSD statistical analysis at a 5% significance level. ⢠TSR: d2s value of 9.3% (Azari 2010). ⢠Wet MR stiffnesses: ANOVA and Tukeyâs HSD statistical analysis at a 5% significance level. ⢠MR-ratio: assumed d2s value of 10%. ⢠HWTT SIP: numerical comparison with an allowable dif- ference of 2,000 load cycles based on data from the Texas field project. ⢠HWTT stripping slope: numerical comparison with the allowable difference of 0.2 mm/cycle based on data from the Texas field project. Moisture Susceptibility Table 3-3 summarizes the comparison of WMA versus HMA mixture performance from the four field projects in terms of wet IDT strength and TSR for PMFC cores at construction and after field aging, onsite and offsite PMLC specimens, and LMLC specimens. This same comparison is shown for HWTT SIP and stripping slope in Table 3-4, and Table 3-5 shows the comparisons for wet MR stiffness and MR-ratio for only onsite and offsite PMLC specimens and LMLC specimens. In Tables 3-3, 3-4, and 3-5, red shading indicates decreased WMA performance as compared to HMA, and green shad- ing indicates WMA performance at least equivalent to that of HMA. Tables 3-3, 3-4, and 3-5 also indicate when WMA fails common thresholds even with better or equivalent performance as compared to HMA and when WMA passes common thresholds but exhibits inferior performance as compared to HMA. These common performance thresholds include minimum 80% for TSR and MR-ratio, minimum SIP of 10,000 based on the Iowa specification, and minimum wet IDT strengths of 65 psi and 80 psi for mixtures with unmodi- fied (Iowa) and modified (Montana, New Mexico, and Texas) binders based on averages from the Nevada, Tennessee, and Texas specifications. In the Iowa field project, generally inferior performance was exhibited by WMA with RAP in terms of wet IDT strengths and TSR values of PMFC cores at construction and PMFC cores after winter at 6 months in service. However, there was a significant increase in these parameters for PMFC cores after summer at 12 months in service such that WMA with RAP performance was at least equivalent to HMA with RAP. This same trend was shown for the Texas field project when comparing WMA versus HMA PMFC cores at construction to PMFC cores after summer at 8 months in service in terms of as they experienced approximately the same level of binder aging, with the PMFC cores possibly aging more during transportation to the paving site. Dry MR stiffness results from the Texas field project verified this expected behav- ior, while corresponding results from the Iowa field proj- ect showed a different trend. For the Iowa field project, the onsite PMLC specimens showed higher dry MR stiffnesses as compared with those for the PMFC cores at construction. To evaluate these differences with respect to binder stiffness and aggregate orientation, binders were extracted and recovered from HMA and Evotherm WMA onsite PMLC specimens and PMFC cores obtained from both projects. The stiffness of the extracted binders was then evaluated with the DSR in terms of Gâ/sin d. In addition, the effect of the aggregate orientation was estimated via image analysis techniques, and differences in AV content were considered. The stiffness of the binder extracted from PMFC cores at construction was higher than the stiffness of the binder extracted from onsite PMLC specimens, as indicated by DSR testing. Thus, the discrepancy in mixture and binder stiff- ness between PMFC cores at construction and onsite PMLC specimens was likely due to other factors that overcome the difference in binder stiffness, such as mixture anisotropy induced by different compaction methods (i.e., laboratory versus field) and different AV. Based on image analysis tech- niques, the onsite PMLC specimens showed less horizontal anisotropy as compared with PMFC cores at construction, as expected, resulting in less resistance to the diametral load in the MR test. Higher AV may also significantly reduce the mix- ture stiffness in terms of MR. Therefore, mixture anisotropy and overall AV had a greater effect on mixture stiffness than the increasing binder stiffness. WMA Moisture Susceptibility The objectives of the WMA moisture-susceptibility experi- ment were to (1) evaluate moisture susceptibility of WMA as compared with that of HMA based on standard labora- tory tests and (2) examine the effects of anti-stripping agents to improve moisture susceptibility. HMA and WMA per- formance was compared in terms of moisture susceptibil- ity evaluated on the basis of wet IDT strength and TSR, wet MR stiffness and MR-ratio, and HWTT SIP and stripping slope. Different specimen types were also compared within each mixture type to examine important differences in (1) LMLC specimens used in mix design, (2) PMLC speci- mens used in QA, (3) PMLC specimens reheated for offsite compaction, and (4) field performance as determined by laboratory testing of PMFC cores. Appendix B provides detailed results for the different per- formance parameters by mixture type. Summary results are presented in this section for this experiment in tables of the
Location Specimen Type Wet IDT TSR Evotherm Sasobit Foaming Evotherm Sasobit Foaming Iowa Cores at construction Fail N/A N/A Cores after winter Fail Cores after summer Onsite PMLC Pass Pass Offsite PMLC Fail LMLC Fail Montana Cores at construction Cores after winter Onsite PMLC Fail Fail Fail Fail Fail Fail Offsite PMLC Pass Pass Pass Texas Cores at construction Fail N/A Fail Fail N/A Cores after summer Onsite PMLC Fail Fail Offsite PMLC Pass Fail Fail LMLC New Mexico Cores at construction Pass N/A N/A Onsite PMLC Offsite PMLC LMLC Fail Fail Fail Key WMA HMA WMA < HMA Table 3-3. Summary trends for IDT strength results. Location Specimen Type HWTT SIP HWTT Stripping Slope Evotherm Sasobit Foaming Evotherm Sasobit Foaming Iowa Cores at construction Fail Fail N/A N/A Cores after winter Fail Fail Cores after summer Fail Fail Onsite PMLC Fail Fail Offsite PMLC N/A N/A LMLC Fail Fail Montana Cores at construction Cores after winter Fail Onsite PMLC Offsite PMLC Pass Texas Cores at construction N/A N/A Cores after summer Onsite PMLC Fail Offsite PMLC Pass LMLC New Mexico Cores at construction N/A N/A Onsite PMLC Offsite PMLC LMLC Key WMA HMA WMA < HMA Table 3-4. Summary trends for hWTT results.
36 ing mixtures (to 275°F [135°C] as for HMA) that resulted in unexpected inferior performance. For this same comparison in the Iowa field project, adequate (at least equivalent) perfor- mance was exhibited by WMA in terms of wet IDT strengths and TSR values only after reheating to compact off site. This same trend was shown in the New Mexico field project for WMA foaming with RAP in terms of wet MR and MR-ratio, while WMA Evotherm® 3G with RAP showed no difference. This same increase in performance after reheating was seen for WMA Evotherm DAT⢠in the Texas field project for wet MR and WMA foaming in the Montana field project for MR-ratio, while most of the other WMA mixtures showed no difference as compared to HMA for these performance parameters. Exceptions where unexpected inferior performance as com- pared to HMA was obtained after reheating were observed in the case of WMA foaming in the Texas field project for MR-ratio and WMA Evotherm® 3G in the Montana field proj- ect for wet MR. This same phenomenon of unexpected inferior performance after reheating the plant mix was exhibited by WMA Sasobit® for both wet IDT strength and TSR and WMA Evotherm® 3G for only wet IDT strength in the Montana field project. WMA foaming in this field project showed no dif- ference with HMA for both of these parameters, and WMA Evotherm® 3G showed no difference for TSR value. For the Texas field project, generally inferior performance of WMA was noted in terms of the HWTT parameters for both onsite and offsite PMLC specimens, with only WMA Evotherm DAT⢠showing an increase in performance with reheat- HWTT SIP and stripping slope. For the Montana field project, at least equivalent performance of WMA as compared to HMA was shown for PMFC cores at construction and after winter at 6 months in service for wet IDT strength, TSR, and HWTT performance parameters. This same trend was observed for the Texas field project, but only for wet IDT strength and TSR for all except the WMA foaming PMFC cores at construction. Again, the same trend was shown for the Iowa field project for all PMFC cores in terms of HWTT SIP, but for stripping slope, WMA Sasobit® with RAP exhibited inferior performance as compared to HMA with RAP for all PMFC cores, and WMA Evotherm® 3G with RAP exhibited generally adequate perfor- mance for PMFC cores. With only PMFC cores at construc- tion available in the New Mexico project, WMA with RAP had adequate (at least equivalent) performance as compared to HMA with RAP for both HWTT parameters and TSR values; wet IDT strength with inadequate performance was noted for Evotherm® 3G with RAP, but the value was still above the 80 psi common threshold for modified binders. Comparing onsite and offsite PMLC specimens, there was no difference between WMA with RAP and HMA with RAP for the Iowa field project in terms of wet MR and MR-ratio and for the New Mexico field project in terms of wet IDT strength and TSR and HWTT SIP and stripping slope. Generally, there was no difference between WMA and HMA for these speci- mens for the Texas field project for wet IDT strength and TSR and for the Montana field project for the HWTT parameters. Exceptions were generally seen when reheating WMA foam- Location Specimen Type Wet MR MR-ratio Evotherm Sasobit Foaming Evotherm Sasobit Foaming Iowa Onsite PMLC N/A Fail Fail N/A Offsite PMLC Fail Fail LMLC Fail Fail Montana Onsite PMLC Pass Offsite PMLC Texas Onsite PMLC N/A Fail N/A Fail Offsite PMLC Fail LMLC New Mexico Onsite PMLC N/A N/A Offsite PMLC LMLC Fail Fail Key WMA HMA WMA < HMA Table 3-5. Summary trends for MR results.
37 decreased performance as compared to the design mixture, yellow shading indicates equivalent performance as com- pared to the design mixture, and green shading indicates improved performance as compared to the design mixture. For this experiment, LMLC specimens were produced for the Iowa and Texas field projects to evaluate the effect of adding hydrated lime or LAS in terms of wet IDT strength and TSR and wet MR stiffness and MR-ratio. Before compaction, the loose mix was conditioned according to the proposed labo- ratory-conditioning experiment protocol. In general, when looking at all of the performance param- eters evaluated, the addition of either hydrated lime or LAS did not improve the performance of either WMA or HMA across all parameters (wet IDT strength, wet MR, and MR-ratio), although some benefits were noted for some mixtures for some of these parameters. In terms of the traditional param- eter for assessing moisture susceptibility (TSR), addition of LAS resulted in improved performance for four out of the six mixtures evaluated. WMA Sasobit® with RAP in the Iowa field project and WMA foaming in the Texas field project also ben- efitted in terms of this parameter and wet MR with the addi- tion of hydrated lime. Adding hydrated lime also resulted in improved performance for WMA foaming in the Texas field project for MR-ratio, and adding LAS resulted in improved performance for WMA Sasobit® with RAP in the Iowa field project for MR-ratio and for WMA Evotherm DAT⢠in the Texas field project for wet IDT strength. HMA with RAP in the Iowa field project also showed improved performance with hydrated lime for wet IDT strength. The most benefits from the addition of anti-stripping agents were shown for the WMA foaming from the Texas project and the WMA Sasobit® with RAP from the Iowa field project. These mixtures were weaker in terms of moisture-susceptibility parameters, as discussed in detail in Appendix B. Finally, the incorporation of additional ing for the stripping slope. Finally, for the Iowa field proj- ect where HWTT results were not available for offsite PMLC specimens, inferior performance was shown in terms of strip- ping slope, but adequate performance was noted for SIP. LMLC specimens were available for the Iowa, Texas, and New Mexico field projects. For the New Mexico field project, there were no differences noted between WMA with RAP and HMA with RAP for any of the moisture susceptibility parame- ters evaluated. This same trend was noted for both WMA mix- tures with RAP in the Iowa field project for both ratios (TSR and MR-ratio) and SIP, but inferior performance as compared to HMA with RAP was shown for wet IDT strength, wet MR, and stripping slope. For the Texas field project, WMA foam- ing exhibited inferior performance as compared to HMA for all of the moisture-susceptibility parameters evaluated, while WMA Evotherm DAT⢠exhibited inferior performance for both HWTT parameters and TSR. Based on the complete set of laboratory performance tests for all four field projects, WMA can be more moisture suscepti- ble in its early life prior to a summer of aging. However, WMA generally exhibits adequate (at least equivalent) performance as compared to HMA in terms of moisture susceptibility mea- sured in the laboratory after a summer of aging. The use of anti-stripping agents may reduce this susceptibility. Finally, there are differences in offsite and onsite PMLC specimens in terms of laboratory-measured moisture susceptibility, with the artificial aging due to reheating generally producing specimens with improved resistance to moisture damage. Effect of Anti-Stripping Agents Tables 3-6 and 3-7 summarize the comparison of WMA and HMA design mixtures with those with added anti- stripping agents. In Tables 3-6 and 3-7, red shading indicates Location Mixture Type Wet IDT TSR Hydrated Lime LAS Hydrated Lime LAS Iowa HMA+RAP Evotherm 3G+RAP Sasobit+RAP Texas HMA Evotherm DAT Foaming Key AS = Design AS < Design AS > Design Table 3-6. Summary trends for IDT strength results from the anti-stripping agent experiment.
38 generally able to represent early-life field performance (PMFC cores at construction and after winter at 6 months in service for WMA Evotherm® 3G); for two WMAs, the onsite PMLC specimens exhibited lower wet IDT strengths. For the third WMA for this field project (i.e., WMA foaming), the PMFC cores at construction and after winter at 6 months in service had wet IDT strengths between the onsite PMLC specimens and the offsite PMLC specimens, with the latter showing the largest IDT strength for the Montana WMA foaming. When comparing TSR values, the LMLC specimens suc- cessfully represented the early-life field performance for the Iowa field project with equivalent values based on the d2s value for this test method for PMFC cores at construc- tion and for the Texas field project with values between the PMFC cores at construction and those after summer at 8 months in service. For the New Mexico project, LMLC specimens did not represent PMFC cores at construction. In addition, onsite and offsite PMLC specimens exhibited equivalent TSR values (based on the d2s value) for both WMAs in both the Iowa and Texas field projects and one WMA in the New Mexico field project. However, for all three WMAs in the Montana field project and the other WMA in the New Mexico field project, these types of specimens were not equivalent in terms of TSR. For wet MR, LMLC specimens for the Iowa project were not representative of the onsite or offsite PMLC specimens that exhibited increased wet MR values for both WMAs. Better representation by the LMLC specimens of the onsite and offsite PMLC specimens was shown for both WMAs in the Texas field project. In addition, the onsite and offsite PMLC specimens produced statistically equivalent wet MR values for all of the WMAs, except WMA Evotherm in both the Texas and Montana field projects and WMA foaming with RAP in the New Mexico field project. This same general agreement LAS to WMA Evotherm from either the Iowa or Texas field projects showed a counterproductive effect, decreasing perfor- mance in four cases. This could be attributed to the incompat- ibility between the amine compounds in Evotherm with the LAS components used in this study. Based on the mixed results shown, the selection of an opti- mum anti-stripping agent does not appear to be related to WMA technology or different from the process used for HMA. As for HMA, an important factor to consider is the aggregate type; LAS agents are likely more sensitive to the com- patibility with the aggregate and the WMA additive type than hydrated lime. Effect of Specimen Type Tables 3-8 through 3-10 summarize the comparison of specimen types from the four field projects in terms of wet IDT strength and TSR, HWTT SIP and stripping slope, and wet MR and MR-ratio, respectively. The analysis focused on these comparisons for the WMA mixtures. For both WMAs from both the Iowa and Texas field proj- ects, the LMLC specimens successfully represented the early- life field performance (PMFC cores at construction and after winter at 6 months in service for Iowa) in terms of wet IDT strength. For the Iowa field project, the onsite and off- site PMLC specimens for both WMAs with RAP generally represented the PMFC cores after field aging over a summer (12 months in service) for this parameter. For the Texas field project, the PMFC cores after summer at 8 months in ser- vice for both WMAs exhibited increased wet IDT strength as compared to onsite and offsite PMLC specimens that also represented the early-life field performance (PMFC cores at construction). For the Montana field project, which did not include LMLC specimens, the offsite PMLC specimens were Location Mixture Type Wet MR MR-Ratio Hydrated Lime LAS Hydrated Lime LAS Iowa HMA+RAP Evotherm 3G+RAP Sasobit+RAP Texas HMA Evotherm Foaming Key AS = Design AS < Design AS > Design Table 3-7. Summary trends for MR results from anti-stripping agent experiment.
39 onsite and offsite PMLC specimens for this parameter. For stripping slope, only one WMA in the Texas field project and both WMAs in the New Mexico field project showed agree- ment in terms of LMLC specimens representing early-life field performance (PMFC cores at construction). In general, strip- ping slope seemed to be a more sensitive parameter than SIP for identifying differences in mixture and specimen types. WMA Performance Evolution The objectives of the two-phase WMA performance evo- lution experiment were to (1) determine when (or if) prop- erties of HMA and WMA converged and (2) evaluate the evolution of performance of WMA as compared to HMA in the early life of the pavement. In the first phase, the moisture susceptibility of WMA was determined in terms of a critical between onsite and offsite PMLC specimens was observed for MR-ratio for all WMAs, except WMA Evotherm® 3G from the Montana field project and WMA foaming from both the Texas and New Mexico field projects. For the HWTT parameters (SIP and stripping slope), LMLC specimens successfully represented the early-life field per- formance (PMFC cores at construction and after winter at 6 months in service for Iowa) in terms of SIP for all WMAs in all field projects, except WMA foaming in the Texas field project. All WMAs, except WMA Evotherm DAT⢠in the Texas field project, also showed agreement in this parameter between onsite and offsite PMLC specimens. Agreement between these specimen types was also shown for stripping slope for two WMAs in the Montana field project and both WMAs with RAP in the New Mexico field project. The WMAs in both the Iowa and Texas field projects did not show agreement between Location Specimen Type Wet IDT TSR Evotherm Sasobit Foaming Evotherm Sasobit Foaming Iowa Cores at construction B C N/A N/A Cores after winter B C Cores after summer A A Onsite PMLC A B Offsite PMLC A A LMLC B C Montana Cores at construction A A-B B Cores after winter A A B Onsite PMLC B C C Offsite PMLC A B A Texas Cores at construction C N/A B N/A Cores after summer A A Onsite PMLC B-C B Offsite PMLC B B LMLC B-C B New Mexico Cores at construction A N/A A N/A Onsite PMLC A B Offsite PMLC A C LMLC B D Key TSR LMLC = Cores Different Offsite = Onsite PMLC Table 3-8. Effect of specimen type based on IDT strength results.
40 ceptibility evaluated on the basis of wet IDT strength, TSR, wet MR stiffness, MR-ratio, HWTT SIP, and stripping slope after LTOA of compacted specimens at different time periods. Appendix C provides detailed results for the evolution of dry MR stiffness and moisture susceptibility parameters mea- sured in laboratory tests due to field and laboratory aging of age to reach a dry MR stiffness equivalent to that of an HMA control mixture. The evolution of dry MR stiffness in HMA and WMA in the field and laboratory were evaluated sep- arately, followed by the correlation of laboratory and field aging. In the second phase, HMA and WMA performance was compared in terms of dry MR stiffness and moisture sus- Location Specimen Type Wet MR MR-ratio Evotherm Sasobit Foaming Evotherm Sasobit Foaming Iowa Onsite PMLC A A N/A N/A Offsite PMLC A A LMLC B B Montana Onsite PMLC A A A Offsite PMLC B A A Texas Onsite PMLC B N/A A-B N/A Offsite PMLC A A LMLC A-B B New Mexico Onsite PMLC A N/A B N/A Offsite PMLC A A LMLC B B Key MR-ratio Different Offsite = Onsite PMLC Table 3-9. Effect of specimen type based on MR results. Location Specimen Type HWTT SIP HWTT Stripping Slope Evotherm Sasobit Foaming Evotherm Sasobit Foaming Iowa Cores at construction N/A N/A Cores after winter Cores after summer Onsite PMLC Offsite PMLC LMLC Montana Cores at construction Cores after winter Onsite PMLC Offsite PMLC Texas Cores at construction N/A N/A Cores after summer Onsite PMLC Offsite PMLC LMLC New Mexico Cores at construction N/A N/A Onsite PMLC Offsite PMLC LMLC Key LMLC = Cores Different Offsite = Onsite PMLC Table 3-10. Effect of specimen type based on hWTT results.
41 In addition, onsite PMLC specimens from the Texas field project conditioned 1â2 h at Tc as compared to those condi- tioned 0â1 h at the same temperature exhibited equivalent dry MR stiffnesses. Equivalent stiffnesses were also shown for onsite PMLC specimens and PMFC cores at construction for the Texas field project, indicating the same level of mix- ture aging as expected. Conversely, for the Iowa field project, onsite PMLC specimens exhibited higher MR stiffnesses than PMFC cores at construction. These differences were attrib- uted to aggregate anisotropy resulting from different com- paction methods and total AV in the specimens. From the dry MR stiffness results, it can be inferred that HMA and WMA PMFC cores from both field projects expe- rienced a significant increase in stiffness with aging in the field. The increase in stiffness after a summer was more sig- nificant than that after a winter, probably because of the high in-service temperature and substantial aging experienced by the pavement in the summer. Equivalent stiffnesses between HMA with RAP and WMA with RAP were achieved for PMFC cores after winter at 6 months in service for Iowa, while for the Texas field project, PMFC cores of WMA Evotherm DAT⢠were less stiff than those of HMA and WMA foaming. Thus, in the case of Texas, PMFC cores over a longer service time in the field would be needed to determine the period necessary for the stiffness of HMA and WMA Evotherm DAT⢠to converge. Additionally, a higher rate of increase in MR stiffness was shown for WMA pavements as compared to HMA pavements for both Iowa and Texas field projects, with the exception of WMA Evotherm® 3G with RAP for the Iowa field project. Laboratory Aging Figures 3-3 and 3-4 indicate that, for both the Iowa and Texas field projects, the dry MR stiffness of HMA and WMA LMLC specimens increased significantly after subjecting HMA and WMA. Summary results are presented in this sec- tion for both phases of this experiment. Phase I Field Aging The period in the field where equivalent dry MR stiffness between HMA and WMA was achieved was determined for the Iowa and Texas field projects, respectively, from Figure 3-1 and Figure 3-2. For Iowa (Figure 3-1), the initial stiffness of PMFC cores for HMA with RAP was higher than that for WMA Sasobit® with RAP and equivalent to that for WMA Evotherm® 3G with RAP. For PMFC cores after winter at 6 months in ser- vice, equivalent stiffness between HMA with RAP and WMAs with RAP was achieved. For Texas (Figure 3-2), the stiffness of PMFC cores at construction for HMA was higher than both WMA mixtures, while the stiffness of WMA foaming was higher than that of WMA Evotherm DATâ¢. After summer at 8 months in service, the stiffness of PMFC cores for all mixtures increased significantly, and equivalent stiffness was achieved between HMA and WMA foaming. 0 100 200 300 400 500 0 2 4 6 8 10 12 14 R es il ie n t M od ul us (k si ) Time in the Field (months) HMA+RAP Evotherm 3G+RAP Sasobit+RAP Figure 3-1. Evolution of MR stiffness with field aging for the Iowa field project. 0 100 200 300 400 500 600 700 800 900 0 2 4 6 8 10 12 14 R es il ie n t M od ul us (k si ) Time in the Field (months) HMA Evotherm DAT Foaming Figure 3-2. Evolution of MR stiffness with field aging for the Texas field project. Figure 3-3. Evolution of MR stiffness with laboratory aging at 140î¸F (60î¸C) for the Iowa field project. 0 100 200 300 400 500 600 700 800 900 0 2 4 6 8 10 12 14 16 R es il ie n t M od ul us (k si ) Aging Time in the Laboratory (weeks) HMA+RAP Evotherm 3G+RAP Sasobit+RAP
42 5 days at 185°F (85°C) by AASHTO R 30 was selected as the third protocol. Correlation of Laboratory and Field Aging Table 3-11 summarizes the comparison of dry MR stiffnesses for LMLC specimens with different laboratory aging protocols versus those for PMFC cores after different in-service times, including statistical analysis by Tukeyâs HSD test at a 5% sig- nificance level to compare the different laboratory aging pro- tocols. In Table 3-11, red shading indicates statistically higher MR stiffness values for LMLC specimens as compared to PMFC cores, green shading indicates statistically equivalent perfor- mance for these specimen comparisons, and yellow shading indicates that LMLC specimens exhibited statistically lower MR stiffness values for the same comparisons. As shown in Table 3-11, equivalent dry MR stiffness between LMLC specimens with LTOA protocols at 140°F (60°C) for up to 2 weeks and PMFC cores at construction and after a winter (at 6 months in service for Iowa) was shown for most of Iowa and Texas mixtures, indicating equivalent initial stiff- ness in the laboratory and field. In addition, the laboratory LTOA protocols at 140°F (60°C) for 4 to 16 weeks were repre- sentative of the field aging experienced by PMFC cores after a summer (at 12 months in service for Iowa and at 8 months in service for Texas). Phase II In Phase II of the WMA performance evolution experi- ment, new sets of LMLC specimens were fabricated and, after compaction, subjected to the three LTOA protocols selected in Phase I prior to being evaluated on performance. The effects of field aging and laboratory LTOA on HMA and WMA performance, the correlation between laboratory the compacted specimens to aging in the laboratory at 140°F (60°C). As shown, the rate of aging or slopes of the piecewise linear relationships were similar for HMA and WMA, with steeper slopes for both types of mixtures during the first week of laboratory aging. To further explore the laboratory aging behavior, an exponential curve was fitted to the dry MR stiff- ness data. Based on these fitted curves, the laboratory aging protocol of 2 weeks at 140°F (60°C) was selected for Phase II of the WMA performance-evolution experiment. This aging period represented the time at which the stiffness of WMA was similar to the initial stiffness of HMA (Iowa field proj- ect) or the stiffness of HMA and WMA converged (Texas field project). Additionally, considering a previous study in Texas on the correlation between laboratory and field aging (Glover et al. 2005), a second laboratory aging protocol of 16 weeks at 140°F (60°C) was selected to characterize the field aging of asphalt pavements approximately 1 to 2 years after construction. The standard laboratory aging protocol of Figure 3-4. Evolution of MR stiffness with laboratory aging at 140î¸F (60î¸C) for the Texas field project. 0 200 400 600 800 1000 1200 0 2 4 6 8 10 12 14 16 R es il ie n t M od ul us (k si ) Aging Time in the Laboratory (weeks) HMA Evotherm DAT Foaming Location Mixture Type LTOA Protocols â Weeks at 140°F (60°C) 0 1 2 4 8 16 0 1 2 4 8 16 0 1 2 4 8 16 vs. PMFC Cores at Construction vs. PMFC Cores after 1st Winter vs. PMFC Cores after 1st Summer Iowa HMA+ RAP Evotherm 3G+RAP Sasobit Texas HMA N/A Evotherm DAT Foaming Key LMLC > PMFC Cores LMLC = PMFC Cores LMLC < PMFC Cores Table 3-11. Summary trends for dry MR stiffness in Phase I of WMA performance evolution.
43 ⢠HWTT stripping slope: numerical comparison with an allowable difference of 0.2 mm/cycle. Effect of Aging on Mixture Performance Table 3-12 summarizes the comparison of Iowa and Texas mixture performance in IDT strength, MR, and HWTT tests for PMFC cores after field aging in the summer and winter versus those at construction. In Table 3-12, red shading indi- cates decreased performance for aged mixtures as compared to those at construction; green shading indicates increased performance with aging; and yellow shading indicates equiv- alent performance with aging. In the Iowa field project for HMA with RAP and two WMAs with RAP, dry and wet IDT strengths of PMFC cores and field aging, and a comparison of HMA versus WMA for each aging stage are provided in this section in summary tables of the trends observed for the different performance parameters measured in laboratory tests. The comparisons in test results shown are based on the following for each test parameter: ⢠Dry and wet IDT strength: ANOVA and Tukeyâs HSD sta- tistical analysis at a 55% significance level. ⢠TSR: d2s value of 9.3% (Azari 2010). ⢠Dry and wet MR stiffnesses: ANOVA and Tukeyâs HSD sta- tistical analysis at a 55% significance level. ⢠MR-ratio: assumed d2s value of 10%. ⢠HWTT SIP: numerical comparison with an allowable dif- ference of 2,000 load cycles. Mixture Test Parameters Iowa Winter Aging Cores @ 6 months Iowa Summer Aging Cores @ 12 months Texas Summer Aging Cores @ 8 months Iowa HMA+RAP/ Texas HMA IDT Dry IDT Strength Wet IDT Strength TSR MR Dry MR Wet MR N/A MR-ratio HWTT SIP N/A Stripping Slope Iowa Evotherm 3G+RAP/ Texas Evotherm DAT IDT Dry IDT Strength Wet IDT Strength TSR MR Dry MR Wet MR N/A MR-ratio HWTT SIP N/A Stripping Slope Iowa Sasobit+RAP IDT Dry IDT Strength N/A Wet IDT Strength TSR MR Dry MR Wet MR N/A MR-ratio HWTT SIP Stripping Slope Texas Foaming IDT Dry IDT Strength N/A Wet IDT Strength TSR MR Dry MR Wet MR N/A MR-ratio HWTT SIP Stripping Slope Key Decreased Performance Increased Performance Equivalent Performance Table 3-12. Summary trends in field aging of PMFC cores.
44 cantly better performance in the HWTT test. For the two WMAs, PMFC cores after summer at 8 months in service had increased SIP values and decreased stripping slopes as com- pared to those at construction, indicating improved resistance to moisture susceptibility. In general, PMFC cores after field aging in the summer (Iowa PMFC cores after 12 months in service and Texas PMFC cores after 8 months in service) had significantly better performance in the laboratory tests as compared to PMFC cores at construc- tion. However, the difference between PMFC cores after field aging in the winter (Iowa PMFC cores after 6 months in service) and those at construction was insignificant. Tables 3-13 through 3-15 summarize the comparison of mixture performance in IDT strength, MR, and HWTT tests for LMLC specimens with LTOA protocols and those with- out LTOA, for Iowa, Texas, and New Mexico mixtures, respec- tively, with colored shading as described previously. For the Iowa field project, the laboratory LTOA protocol of 16 weeks at 140°F (60°C) significantly increased the dry and wet IDT strengths and dry and wet MR stiffnesses of HMA with RAP and two WMAs with RAP but had no significant effect on at construction and PMFC cores after winter at 6 months in service were generally statistically equivalent. However, dry and wet IDT strengths and dry MR stiffnesses for PMFC cores after summer at 12 months in service increased significantly. The TSR values of HMA with RAP for PMFC cores decreased from 91 to 62% as field aging time increased from at construc- tion to after summer at 12 months in service. However, the decrease in TSR values for this same aging period for WMA Evotherm® 3G with RAP and WMA Sasobit® with RAP PMFC cores was insignificant. In the Texas field project for HMA and two WMAs, PMFC cores after summer at 8 months in service had generally higher dry and wet IDT strengths, dry MR stiffnesses, and TSR val- ues as compared to those at construction. The TSR values of PMFC cores at construction for HMA and two WMAs were lower than 70%, while those of PMFC cores after summer at 8 months in service were closer to or above 80%. For all mix- tures in this field project, PMFC cores at construction did not meet the Texas criteria of 20,000 load cycles with less than 0.5 inch (12.5 mm) rut depth. However, PMFC cores after summer at 8 months in service were shown to have signifi- Mixture Test Parameters LTOA 2 weeks @ 60°C LTOA 16 weeks @ 60°C LTOA 5 days @ 85°C HMA+RAP IDT Dry IDT Strength N/A N/A Wet IDT Strength TSR MR Dry MR N/A Wet MR N/A MR-ratio HWTT SIP N/A Stripping Slope Evotherm 3G+RAP IDT Dry IDT Strength N/A N/A Wet IDT Strength TSR MR Dry MR N/A Wet MR N/A MR-ratio HWTT SIP N/A Stripping Slope Sasobit+RAP IDT Dry IDT Strength N/A N/A Wet IDT Strength TSR MR Dry MR N/A Wet MR N/A MR-ratio HWTT SIP N/A Stripping Slope Key Decreased Performance Increased Performance Equivalent Performance Table 3-13. Summary trends in laboratory aging of LMLC specimens for the Iowa field project.
45 (mixtures and LTOA protocols), LMLC specimens with labo- ratory LTOA protocols had higher SIP and lower stripping slope than those without LTOA. For the New Mexico field project, the same trends as for both the Iowa and Texas field projects were shown only for the dry and wet MR stiffnesses (increased with aging) for HMA with RAP and two WMAs with RAP after LTOA protocols of 2 weeks at 140°F (60°C) and 5 days at 185°F (85°C). MR-ratios also increased with aging for all three mixtures after the LTOA protocol of 2 weeks at 140°F (60°C) and for HMA with RAP after LTOA protocol of 5 days at 185°F (85°C), but unexpect- edly, no significant aging effect was shown for this parameter for the longer LTOA protocol for both WMAs with RAP. All mixtures also exhibited no significant aging effect on either HWTT parameter (SIP and stripping slope) after both LTOA protocols of 2 weeks at 140°F (60°C) and 5 days at 185°F (85°C). For dry and wet IDT strengths, there was a change in the aging effect for LMLC specimens after the LTOA protocol of 2 weeks at 140°F (60°C) and after the LTOA protocol of 5 days at 185°F (85°C) with the HMA with RAP, and one WMA with RAP generally showed no effect after the shorter increasing the TSR values or MR-ratios of LMLC specimens. Additionally, the increase in mixture dry MR stiffness from the LTOA protocol of 16 weeks at 140°F (60°C) was more signifi- cant than that from LTOA protocol of 2 weeks at 140°F (60°C). For the Texas field project, the same trends as for the Iowa field project were shown for dry and wet IDT strengths and dry and wet MR stiffnesses (increased with aging) and for TSR values and MR-ratios (no change with aging) for HMA and two WMAs with the LTOA protocol of 16 weeks at 140°F (60°C), LTOA protocol of 2 weeks at 140°F (60°C), and LTOA protocol of 5 days at 185°F (85°C). The increase in IDT strength and MR stiffness after the LTOA protocol of 5 days at 185°F (85°C) was significantly greater than or equivalent to that after LTOA protocol of 2 weeks at 140°F (60°C) for HMA. For the two WMAs, the difference between these two aging protocols was less significant. For all mixtures in the Texas field project, LMLC specimens without LTOA did not meet the Texas criteria of 20,000 load cycles with less than 0.5 inch (12.5 mm) rut depth. However, LMLC specimens with laboratory LTOA protocols were shown to have signifi- cantly better performance in the HWTT test. For all cases Mixture Test Parameters LTOA 2 weeks @ 60°C LTOA 16 weeks @ 60°C LTOA 5 days @ 85°C HMA IDT Dry IDT Strength Wet IDT Strength TSR MR Dry MR Wet MR MR-ratio HWTT SIP N/A Stripping Slope Evotherm DAT IDT Dry IDT Strength Wet IDT Strength TSR MR Dry MR Wet MR MR-ratio HWTT SIP N/A Stripping Slope Foaming IDT Dry IDT Strength Wet IDT Strength TSR MR Dry MR Wet MR MR-ratio HWTT SIP N/A Stripping Slope Key Decreased Performance Increased Performance Equivalent Performance Table 3-14. Summary trends in laboratory aging of LMLC specimens for the Texas field project.
46 these comparisons, and red shading indicates that LMLC specimens exhibited increased performance for the same comparisons. For the Iowa field project with limited data available, LTOA protocol of 16 weeks at 140°F (60°C) produced LMLC specimens with increased or equivalent performance as com- pared to PMFC cores after field aging for all performance parameters for both HMA with RAP and two WMAs with RAP. A similar trend was generally shown for dry MR stiff- ness for LMLC specimens with LTOA protocol of 2 weeks at 140°F (60°C). For some performance parameters with labora- tory aging, increased properties were shown as compared to PMFC cores after winter at 6 months in service, but the laboratory LTOA protocol produced LMLC specimens with equivalent properties with further field aging as compared to PMFC cores after summer at 12 months in service. For TSR values for HMA with RAP and one Evotherm® 3G with RAP, the opposite trend was observed. For the Texas field project (Table 3-17), the LTOA protocols of 16 weeks at 140°F (60°C) and 5 days at 185°F (85°C) produced LMLC specimens with increased or equivalent performance as protocol but increased IDT strengths after the longer proto- col. For the other WMA with RAP, there was no aging effect on IDT strengths for either LTOA protocol. The TSR value for this same WMA with RAP also had no aging effect for either LTOA protocol, and the HMA with RAP showed increased TSR values for both LTOA protocols. The other WMA with RAP exhibited an increased TSR value for the shorter LTOA protocol, but unexpectedly, there was no aging effect for the longer protocol. In general, for all Iowa, Texas, and New Mexico mixtures, LMLC specimens with different LTOA protocols in this study had significantly better performance than those without LTOA, indicating the significant effect of laboratory LTOA in increasing mixture performance. Tables 3-16 and 3-17 summarize the comparison of mix- ture performance in IDT strength, MR, and HWTT tests for PMFC cores after aging in the field and LMLC specimens with LTOA protocols, for Iowa and Texas mixtures, respec- tively. In these tables, yellow shading indicates decreased per- formance for LMLC specimens as compared to aged PMFC cores, green shading indicates equivalent performance for Mixture Test Parameters LTOA 2 weeks @ 60°C LTOA 5 days @ 85°C HMA+RAP IDT Dry IDT Strength Wet IDT Strength TSR MR Dry MR Wet MR MR-ratio HWTT SIP Stripping Slope Evotherm 3G+RAP IDT Dry IDT Strength Wet IDT Strength TSR MR Dry MR Wet MR MR-ratio HWTT SIP Stripping Slope Foaming+RAP IDT Dry IDT Strength Wet IDT Strength TSR MR Dry MR Wet MR MR-ratio HWTT SIP Stripping Slope Key Decreased Performance Increased Performance Equivalent Performance Table 3-15. Summary trends in laboratory aging of LMLC specimens for the New Mexico field project.
47 Comparison of WMA vs. HMA Table 3-18 summarizes the comparison of WMA and HMA with different field aging times and laboratory LTOA proto- cols in the Iowa and Texas field projects. Red shading indi- cates decreased performance for WMA as compared to HMA; green shading indicates increased or equivalent performance for WMA as compared to HMA. For the Iowa field project, PMFC cores at construction and after winter at 6 months in service for two WMAs with RAP exhibited increased or equivalent performance as compared to those of HMA with RAP for dry MR stiffness and dry IDT strength. Decreased performance was shown for PMFC cores for wet IDT strength and TSR, and these mixtures improved in terms of both of these performance parameters with field aging after a summer at 12 months in service. All TSR values of PMFC cores except those with WMA Sasobit® with RAP after winter at 6 months in service and HMA with RAP after summer at 12 months in service were higher than 70%. In addition, the LTOA protocol of 16 weeks at 140°F (60°C) produced LMLC specimens with compared to PMFC cores after summer at 8 months in service for most of the performance parameters for HMA and both WMAs. Decreased performance as compared to PMFC cores after field aging was shown only for dry IDT strength for HMA after LTOA of 5 days at 185°F (85°C) and for TSR for WMA foaming after LTOA of 16 weeks at 140°F (60°C). Both WMAs after LTOA of 2 weeks at 140°F (60°C) also exhibited decreased performance for most performance parameters, whereas the HMA exhibited increased or equivalent performance for most parameters after this shorter aging protocol. Based on these results, laboratory LTOA protocols can be used in conjunction with the STOA proposed in this project to capture the evolution of WMA performance in early life. General trends in the test results for both field projects showed that, compared to PMFC cores after field aging, LMLC speci- mens with LTOA protocols of 16 weeks at 140°F (60°C) and 5 days at 185°F (85°C) exhibited increased or equivalent per- formance. On the other hand, WMAs with LTOA protocol of 2 weeks at 140°F (60°C) showed decreased performance in the selected laboratory tests. Mixture Test Parameters LTOA 2 weeks @ 60°C LTOA 16 weeks @ 60°C LTOA 5 days @ 85°C HMA+RAP IDT Dry IDT Strength N/A N/A Wet IDT Strength TSR W S MR Dry MR W S N/A Wet MR N/A MR-ratio HWTT SIP N/A Stripping Slope Evotherm 3G+RAP IDT Dry IDT Strength N/A W S N/A Wet IDT Strength TSR W S MR Dry MR N/A Wet MR N/A MR-ratio HWTT SIP N/A Stripping Slope Sasobit+RAP IDT Dry IDT Strength N/A W S N/A Wet IDT Strength W S TSR MR Dry MR W S N/A Wet MR N/A MR-ratio HWTT SIP N/A Stripping Slope Key Increased Performance Equivalent Performance Decreased Performance Note: W: field aging in the winter, PMFC cores after winter at 6 months in service; S: field aging in the summer, PMFC cores after summer at 12 months in service. Table 3-16. Summary trends in laboratory vs. field aging for the Iowa field project.
48 lent performance was exhibited by LMLC specimens of both WMAs in terms of wet and dry IDT strength, SIP, and strip- ping slope. Mixed results in terms of improved WMA per- formance were shown for these two longer laboratory LTOA protocols for wet and dry MR stiffness, MR-ratio, and TSR. All WMA foaming LMLC specimens, except those subjected to the LTOA protocol of 5 days at 185°F (85°C), had the lowest TSR values of all mixture types and lower than the minimum threshold of 80% suggested by AASHTO T 283. WMA foam- ing also had the lowest MR ratio values for all LMLC speci- mens with and without LTOA protocols. For the New Mexico field project with only PMFC cores at construction available, WMA Evotherm® 3G with RAP generally exhibited decreased performance as compared to HMA with RAP for many of the performance parameters, while WMA foaming with RAP exhibited increased or equiv- alent performance for the same parameters. For both WMAs, increased or equivalent performance was shown for TSR, SIP, and stripping slope. All laboratory LTOA protocols examined for the New Mexico field project resulted in LMLC specimens with increased or equivalent performance for both WMAs with RAP as compared to HMA with RAP for all perfor- mance parameters except TSR for WMA foaming with RAP improved and increased or equivalent performance for both WMAs with RAP as compared to HMA with RAP for all per- formance parameters except dry MR stiffness and wet IDT strength for WMA Sasobit® with RAP. These same WMAs with RAP exhibited decreased performance as compared to HMA with RAP for wet and dry IDT strength and wet and dry MR stiffness with LMLC specimens with no LTOA. Equivalent TSR and MR-ratio values between HMA with RAP and two WMAs with RAP were obtained for LMLC specimens with no LTOA and with LTOA of 16 weeks at 140°F (60°C). For the Texas field project, field aging after summer at 8 months in service produced PMFC cores with improved and increased or equivalent performance for both WMAs as compared to HMA for TSR, dry MR stiffness, SIP, and strip- ping slope. Increased or equivalent performance for both WMAs as compared to HMA was exhibited for all PMFC cores for wet IDT strength. For most of the performance parameters, LMLC specimens with no LTOA or with LTOA protocol of 2 weeks at 140°F (60°C) for at least one WMA showed decreased performance as compared to HMA. But after LTOA protocols of either 16 weeks at 140°F (60°C) or 5 days at 185°F (85°C), improved and increased or equiva- Mixture Test Parameters LTOA 2 weeks @ 60°C LTOA 16 weeks @ 60°C LTOA 5 days @ 85°C HMA IDT Dry IDT Strength Wet IDT Strength TSR MR Dry MR Wet MR N/A MR-ratio HWTT SIP N/A Stripping Slope Evotherm DAT IDT Dry IDT Strength Wet IDT Strength TSR MR Dry MR Wet MR N/A MR-ratio HWTT SIP N/A Stripping Slope Foaming IDT Dry IDT Strength Wet IDT Strength TSR MR Dry MR Wet MR N/A MR-ratio HWTT SIP N/A Stripping Slope Key Increased Performance Equivalent Performance Decreased Performance Table 3-17. Summary trends in laboratory vs. field aging for the Texas field project.
49 In general, the initial performance of HMA PMFC cores and LMLC specimens without field and laboratory aging was better than the performance of the WMA mixtures. However, the dif- ference was reduced with field aging and laboratory LTOA. Addi- tionally, better or equivalent performance of WMA versus HMA was achieved for several field and laboratory aging conditions. after LTOA of 2 weeks at 140°F (60°C) and MR-ratio for WMA Evotherm® 3G with RAP after LTOA of 5 days at 185°F (85°C). In addition, inadequate performance based on the minimum TSR threshold of 80% for TSR was indicated for HMA with RAP and both WMAs with RAP for LMLC specimens without LTOA and after LTOA of 5 days at 185°F (85°C) and for WMA foaming with RAP for all LTOA protocols. Table 3-18. Summary trends of WMA vs. hMA performance evolution. Aging Stage Test Parameters Iowa WMA vs. HMA Texas WMA vs. HMA New Mexico WMA vs. HMA PMFC Cores @ Construction IDT Dry IDT Strength E F Wet IDT Strength E S E F TSR E F MR Dry MR E F E F Wet MR N/A MR-ratio HWTT SIP N/A Stripping Slope E F PMFC Cores after 1st Summer Field Aging Iowa: after 12 months Texas: after 8 months IDT Dry IDT Strength N/A Wet IDT Strength TSR MR Dry MR Wet MR N/A MR-ratio HWTT SIP N/A Stripping Slope PMFC Cores after 1st Winter Field Aging Iowa: after 6 months IDT Dry IDT Strength N/A N/A Wet IDT Strength TSR E S MR Dry MR Wet MR N/A MR-ratio HWTT SIP Stripping Slope LMLC No LTOA IDT Dry IDT Strength Wet IDT Strength E F TSR MR Dry MR E F Wet MR E F MR-ratio E F HWTT SIP N/A Stripping Slope LMLC LTOA 2 weeks @ 60°C IDT Dry IDT Strength N/A E F Wet IDT Strength TSR E F MR Dry MR Wet MR MR-ratio E F HWTT SIP Stripping Slope (continued on next page)
50 LMLC LTOA 16 weeks @ 60°C IDT Dry IDT Strength N/A N/A Wet IDT Strength E S TSR E F MR Dry MR Wet MR MR-ratio HWTT SIP N/A Stripping Slope LMLC LTOA 5 days @ 85°C IDT Dry IDT Strength N/A Wet IDT Strength TSR MR Dry MR Wet MR MR-ratio E F E F HWTT SIP Stripping Slope Key Decreased Performance Equivalent or Increased Performance Note: E: Iowa WMA Evotherm® 3G with RAP or Texas WMA Evotherm DAT⢠or New Mexico WMA Evotherm® 3G with RAP; S: Iowa WMA Sasobit® with RAP; F: Texas WMA foaming or New Mexico WMA foaming with RAP. Aging Stage Test Parameters Iowa WMA vs. HMA Texas WMA vs. HMA New Mexico WMA vs. HMA Table 3-18. (Continued). â Wet IDT strength (AASHTO T 283 with one F/T cycle) ⥠65 psi and TSR (AASHTO T 283) ⥠70%. â Wet MR (ASTM D7369, condition by AASHTO T 283 with one F/T cycle) ⥠200 ksi and MR-ratio = wet MR/ dry MR ⥠70%. â HWTT SIP ⥠3,500 cycles and HWTT stripping slope ⤠5.3 mm/cycle. For offsite PMLC specimens of WMA mixtures with- out LTOA by one of the following selected laboratory tests, the following criteria are proposed: â Wet IDT strength (AASHTO T 283) ⥠100 psi and TSR (AASHTO T 283 with one F/T cycle) ⥠70%. â Wet MR (ASTM D7369, condition by AASHTO T 283 with one F/T cycle) ⥠300 ksi and MR-ratio = wet MR/ dry MR ⥠70%. â HWTT SIP ⥠6,000 cycles and HWTT stripping slope ⤠2.0 mm/cycle. If inadequate resistance is indicated without LTOA, WMA mixtures with LTOA of LMLC com- pacted specimens of 5 days at 85°C by AASHTO R 30 by same selected laboratory test to evaluate if a summer of aging prior to winter conditions would mitigate early- life moisture susceptibility: â Wet IDT strength (AASHTO T 283) ⥠115 psi. â Wet MR (ASTM D7369, condition by AASHTO T 283) ⥠450 ksi. â HWTT SIP ⥠12,000 cycles and HWTT stripping slope ⤠1.4 mm/cycle. Revisions to Draft AAShto Standards Appendix F provides revisions to AASHTO R 35 appendix based on the results generated and analyzed in this project and proposed as described in the next chapter. The following revisions are proposed as noted: ⢠Preparation of LMLC specimens of WMA mixtures for moisture-susceptibility performance tests to include short- term conditioning of 2 hours at 240°F (116°C) instead of the compaction temperature. ⢠Preparation of onsite PMLC specimens of WMA mix- tures for moisture-susceptibility tests to include sta- bilizing to 240°F (116°C) instead of the compaction temperature. ⢠Preparation of offsite PMLC specimens of WMA mix- tures for moisture-susceptibility performance tests to include reheating to 240°F (116°C) for all WMA mixtures (except foaming technologies) and to 275°F (135°C) (WMA foaming technologies) instead of the compaction temperature. ⢠Use of proposed moisture-sensitivity criteria instead of 80% TSR by AASHTO T 283. For LMLC specimens or onsite PMLC specimens of WMA mixtures without LTOA by one of the follow- ing selected laboratory tests, the following criteria are proposed:
