Impact of Rejuvenators on Moisture Susceptibility and Cracking in WMA with RAP

Over the past decade, the use of warm mix asphalt (WMA) for asphalt pavement construction has increased in the United States. However, questions remain about the long-term performance and durability of WMA pavements. One key issue is the moisture susceptibility of WMA pavements. Concerns about WMA moisture susceptibility include the possibility that aggregates will be inadequately dried at lower production temperatures and the fact that several WMA technologies introduce additional moisture in the production process. The objectives of National Cooperative Highway Research Program (NCHRP) Project 9-49 were to (1) assess whether WMA technologies adversely affect the moisture susceptibility of asphalt pavements and (2) develop guidelines for identifying and limiting moisture susceptibility in WMA pavements. The research was conducted through coordinated laboratory and field experiments that investigated the potential for moisture susceptibility in WMA compared to hot mix asphalt (HMA). Design of the experiments was guided by a survey of the state departments of transportation and industry on WMA pavement construction and performance. The survey identified no instances of moisture damage to WMA pavements in service through 2010. This negative finding is supported by the results of recently completed NCHRP Project 9-47A, which conducted intensive evaluations of WMA pavements constructed across the United States between 2006 and 2011. Project 9-49 then focused on development of guidelines for WMA mix design and quality control to identify and minimize any possibility of moisture susceptibility. The laboratory experiments evaluated (1) laboratory-conditioning protocols for WMA before moisture susceptibility testing, (2) the ability of standard test methods to detect moisture susceptibility of WMA, and (3) potential differences in WMA moisture susceptibility measured on laboratory-mixed and -compacted specimens; plant-mixed, laboratory-compacted specimens; and plant-mixed, field-compacted cores. The guidelines are presented in the form of a workflow of conditioning protocols and standard test methods that first assess the potential moisture susceptibility of a WMA mix design or field mixture and then recommend remedies to minimize such susceptibility. Specific test thresholds in the guidelines are based on the results of testing of WMA from field projects in Iowa, Montana, New Mexico, and Texas. This report fully documents the research and includes the following Appendixes: Appendix A, Laboratory Conditioning Experiment; Appendix B, Moisture Conditioning Experiment; Appendix C, Performance Evolution Experiment; Appendix D, Construction Reports and Performance of Field Projects; Appendix E, Mixture Volumetrics; Appendix F, Proposed Draft Revisions to the Appendix to AASHTO R 35; Appendix G, Future Work Plan to Evaluate Moisture Susceptibility of HMA and WMA; and Appendix H, Statistical Results. Appendix F is included herein. Appendixes A—E, G, and H are available on the TRB website.

The effects of nano zinc oxide (ZnO) and nano reduced graphene oxide (RGO) on moisture susceptibility property of stone mastic asphalt (SMA)

Since its introduction, warm mix asphalt (WMA) has garnered a lot of attention and interest from the pavement industry as a promising technology to replace the conventional hot mix asphalt (HMA). Despite its many benefits, including reducing emissions and fuel usage, definitive answers on the feasibility of replacing HMA pavements with WMA are yet to be answered. A major concern for WMA is susceptibility to moisture-induced damage. In this research study, mixtures prepared using three WMA technologies- viz. Sasobit, Advera WMA and the Foamer were evaluated for their moisture susceptibility and permanent deformation in comparison with an HMA mixture. Tensile strength ratio (TSR) and asphalt pavement analyzer (APA) tests were conducted on these mixtures. Results show that moisture-based WMA technologies (Advera and Foamer) are more susceptible to moisture damage. However, rut depths evaluated using APA, even for moisture-conditioned specimens, indicated WMA performance on par with that of HMA. Even ...

A study on the moisture damage and rutting resistance of polypropylene modified bituminous mixes with crushed brick aggregate wastes

Effect of recycled additives on pure mode I fracture resistance and moisture susceptibility of hot mix asphalt (HMA): An experimental study using semicircular bending (SCB) and indirect tensile strength (ITS) tests

Using the surface free energy (SFE) method to investigate the effects of additives on moisture susceptibility of asphalt mixtures

This study used a mechanistic framework (i.e., surface free energy) to evaluate the moisture susceptibility of warm mix asphalt (WMA) with three different WMA additives, namely, Sasobit, Advera, and Evotherm. The surface free energy (SFE) components of modified PG64-22 asphalt binder with different percentages of WMA additives and selected aggregates were measured in the laboratory. The wettability, the work of adhesion, the work of debonding, and energy ratios were estimated in order to assess the moisture-induced damage potential of combinations of modified asphalt binders and different aggregates. The results indicate that Sasobit and Advera are able to reduce the moisture susceptibility potential of the mixes, but their use is not recommended with highly acidic aggregates such as granite. Evotherm resulted in the highest increases in wettability, total surface free energy, and increased work of adhesion and a reduction in the work of debonding, resulting in a better possible aggregate coating with asphalt binder and lower moisture susceptibility with all types of tested aggregates relative to those of other WMA additives. Furthermore, tensile strength ratio (TSR) tests were conducted on Advera and Evotherm-modified and neat (unmodified) asphalt mixes, and the results were compared with those from the SFE test. It was found that the SFE approach is a better indicator of moisture susceptibility than the traditional TSR test. The findings of the present study would help the highway engineers and agencies to better understand the moisture damage potential of flexible pavements constructed with WMA technologies.

This study used the cyclic direct tension test, indirect tensile strength test, and Hamburg wheel tracking device (HWTD) test to evaluate the moisture susceptibility of warm-mix asphalt (WMA) mixtures. The stripped areas that were quantified by digital imaging analysis were derived from the cyclic direct tension, indirect tensile strength, and HWTD tests and were compared with the mechanical properties of the mixtures to identify sensitive moisture susceptibility indicators. These methods were applied to a Superpave® 9.5-mm hot-mix asphalt mixture and five corresponding WMA mixtures that used the following technologies: (a) Evotherm 3G that contained a chemical additive, (b) foaming, (c) WMA-A that contained a chemical additive and was under development, (d) WMA-B that contained an organic additive and was under development, and (e) WMA-C that also contained an organic additive (different from that used in WMA-B) and was under development. Fatigue life ratios obtained from the simplified viscoelastic continuum damage model combined with layered viscoelastic analyses were determined to be the most sensitive indicators for moisture susceptibility. The stripping infection points derived from the HWTD tests also showed good sensitivity to moisture conditioning; however, each stripping infection point was affected by the permanent deformation characteristics of a given mixture as well as its moisture susceptibility; therefore, the observation was inconclusive.

Zeolite-Foamed Asphalt (ZFA), as a typical-used Warm Mix Asphalt (WMA) in practice, has significant advantages in environmental friendliness and construction convenience, but its moisture susceptibility is relatively weak. Most of the existing research regarding its moisture susceptibility was carried out by performing macroscopic tests, which are incapable of providing theoretical bases for moisture susceptibility optimisation. This article studies the moisture susceptibility of ZFA from a mesoscopic perspective based on the Surface Free Energy (SFE) concept. To determine the SFE of each composition, sessile drop tests were first conducted on three types of aggregates (i.e., basalt, diabase and granite) and three types of bitumen binder (i.e., virgin binder, SBS modified binder and rubber modified binder), respectively, considering four different zeolite incorporation contents (i.e., 0%, 3%, 6% and 9% by the binder mass). Several SFE-based factors, including work of cohesion, dry work of adhesion, work of debonding, spreading coefficient and a SFE-related energy ratio (EP1), were calculated. These factors were correlated with the mass loss ratio of the binder-aggregate systems obtained through boiling water stripping tests to validate their feasibility in evaluating the moisture susceptibility of ZFA. The results indicate that the increase of the polar component and the decrease of the dispersion component of the binder’s SFE resulting from the zeolite foaming process affect the moisture susceptibility of the ZFA either positively or negatively, depending on the dominated failure mode and the aggregate’s SFE. An aggregate with a higher polar component of the SFE, such as the granite in the present work, is more recommended for preparing ZFA when an interfacial adhesion failure occurs. Dry work of adhesion and EP1 demonstrate good correlations with the mass loss ratios and the correlation coefficients are not lower than 0.8057. ZFA prepared with the rubber-modified binder, granite and 9% zeolite is suggested in the present work. The results can theoretically guide the optimisation of the moisture susceptibility of ZFA in practice.

This paper presents the mechanical properties of porous asphalt (PA) with nanosilica (NS) modified asphalt binder in terms of its Moisture Susceptibility. This test is essential to evaluate the performance of NS-PA towards the resistance of moisture induced damage. Moisture susceptibility can be defined as the loss durability, strength and stiffness of PA due to the existence of moisture, causing the adhesive loss of binder and aggregate. It is interesting to know that the existence of nanoparticle with different proportion can affect the moisture susceptibility behavior of NS-PA. Three different percentages of nanosilica were mixed with PEN 60-70 type of binder in this study. Then, all these blended modified binder were used to prepare PA Grading B specimens using Marshall Mix Design Method. Nanoparticle used in this study was Nanosilica with the average size of 10 to 15 nanometer. In addition, Moisture Susceptibility of NS-PA was evaluated using Indirect Tensile Strength Test, based on Modified Lottman Test. From the result, the maximum TSR value obtained at 2% NS-PA, which was 91%. Meanwhile, for conventional PA (0% NS), TSR value was only 74%. In accordance to AASTHOT283, TSR value should be equal or more than 80% to withstand moisture induced damage. However, for PA, 70% TSR value is consider acceptable due to porous nature of PA that permit water to flow inside the mix. From this result, it was concluded that the optimum amount of NS required for PA to withstand moisture induced damage was 2%. Thus, with proper NS concentration, the performance of PA with NS modified binder in terms of moisture susceptibility can be enhanced.

It is known that the freezing of the road brings high risks to the traffic in winter. However, Traditional deicing technology has low deicing efficiency and severe damage to the road surface. Therefore, the new develop pavement conductive wearing surface with graphite heating film (PCWSG) could be one option to solve this problem. So the main objective of this paper is to investigate the road performance (high-temperature, low-temperature, moisture susceptibility, friction-resistance) of pavement conductive wearing surface with graphite heating film (PCWSG) and then evaluate its deicing potential. In this paper, several tests are conducted to evaluate the performance of PCWSG. The high-temperature performance is conducted by the laboratory wheel-tracking rut test. Low-temperature performance is characterized by the low-temperature bending test. Moisture susceptibility is studied by the freeze-thaw split test. Friction-resistance performance is estimated by the pendulum type friction coefficient measuring instrument and the small acceleration loading device. Furthermore, removing ice potential is studied by asphalt rutting slabs (various gradations) with graphite conductive wearing surface. The results show that pavement conductive wearing surface with graphite heating film (PCWSG) could improve the high-temperature, low-temperature, and friction-resistance compared with the original asphalt mixture. Although moisture susceptibility and wear performance decrease lightly but also satisfy the specification requirement. Moreover, removing ice potential of asphalt slabs with PCWSG results shows that AC-20 asphalt concrete with higher porosity has better deicing and snow removal effect. The PCWSG has lower heating and deicing cost and more effective deicing effects.

Electrolytic additives can be used to accelerate strength gain in cement-modified soils. However, one of the consequences of adding electrolytic additives, such as calcium chloride (CaCl2), is the potential to increase moisture susceptibility. Moisture susceptibility affects the strength of the material and its ability to withstand repeated freeze-thaw cycling. In order to evaluate the moisture susceptibility of soil-cement as a function of calcium chloride, different dosages were tested, i.e. 0% control, 5% and 10% of cement weight, with three different soil types. Samples were subjected to tube suction testing, a method which essentially measures capillary rise in soils and aggregates. The data indicate that calcium chloride has a dosage-dependent influence on the extent of capillary rise. It was also found that different soil types exhibit varying suction behavior. In terms of application of this research, moisture susceptibility analysis should be undertaken to assess whether proposed electrolytic chemical additives are appropriate for a given soil type.

In recent decades, some of the main goals of pavement engineers have been to increase bearing capacity, enhance tensile strength, and improve the moisture susceptibility of asphalt mixtures. Because moisture and frost intensify the damage caused by traffic loads on pavements in cold climates, the life and safety of asphalt pavements in this climate are reduced. Finally, cracking at low temperatures and moisture damage leads to a decrease in the serviceability of asphalt pavement in cold climates relative to temperate climates. Hence, a comprehensive and accurate program is necessary to estimate the fracture toughness and moisture susceptibility of asphalt mixtures in cold climates. In recent years, nanotechnology has become very popular due to its unique features in enhancing the operation of bitumen and asphalt mixtures. For this purpose, in this study, the impact of nano-TiO2 on pavement performance against cracking and moisture susceptibility is investigated. To achieve this objective, SCB specimens were fabricated with different ratios of nano-TiO2 (0.0% and 0.9%) and studied at the three temperatures of −5°C, −15°C, and −25°C under pure mode I, pure mode II, and four distinct mixed-mode (I/II) loading (Me=0.2, Me=0.4, Me=0.6, Me=0.8) for various crack geometry, including vertical and angular cracks for which the crack angle is 45° in samples with angular cracks. In addition, the indirect tensile strength (ITS) test was employed to estimate the moisture susceptibility. The results indicated that modifying the asphalt mixture properties with 0.9% nano-TiO2 had a significant impact on the fracture behavior of the samples in both vertical and angular cracks under all temperatures. Additionally, with the application of nano-TiO2 and decreasing temperature, the fracture toughness of the samples increased. Furthermore, the findings displayed that the employment of 0.9% nano-TiO2 reduced the moisture susceptibility of asphalt mixtures by approximately 6%.

The primary objective of the present study is to evaluate the effectiveness of the widely used moisture conditioning methods for moisture susceptibility evaluation while designing the Foamed Bitumen Stabilised Mixes (FBMs). The effectiveness of three different moisture conditioning methods, such as the conventional 24 h of water soaking, vacuum saturation (AASHTO T283), and ASTM D7870 conditioning (hydrostatic pore pressure) were compared based on their ability to distinguish between moisture susceptible and moisture damage resistant FBMs. It was observed that the ASTM D7870 moisture conditioning method could distinguish between moisture-resistant and moisture-susceptible mixes more effectively compared to the existing 24 h of water-soaking method, and can potentially be a more suitable conditioning method for moisture susceptibility evaluation of FBMs. The study also recommended threshold moisture susceptibility criteria in terms of retained tensile strength (TSR) for the ASTM D7870 conditioning method based on the existing moisture susceptibility criteria for 24 h of water soaking by performing Receiver Operation Characteristics (ROC) analysis on the TSR results. For different TSR criteria of 80%, 70%, and 60% for 24 h of water soaking, the equivalent TSR threshold for ASTM D7870 conditioning is recommended as 60%, 55%, and 50% respectively.

In south China, suffering from the rainiest climate, porous asphalt mixtures have been receiving increasing attention. However, with the increase in the application of pavement and the growth of service life, the importance of the recycling application of old reclaimed porous asphalt pavement (RPAP) has gradually become prominent. Based on this, this paper established RPAP content ranging from 0% to 30% in increments of 5% and designed experimental groups with and without regenerating agent to investigate the effects of RAP content and regenerating agent addition on the high-temperature stability, low- and normal-temperature crack resistance, moisture susceptibility, drainage capacity, and mechanical properties of PAC-13 reclaimed porous asphalt mixtures. Subsequently, the practical performance of PAC-13 RPAP was verified through a pavement test. The results indicate that, as the RPAP content increases, the high-temperature stability and mechanical properties of the recycled mixture improve. Specifically, as the planer content is increased to 30%, the dynamic stability of the regenerated porous asphalt increases by 61.1%, and the dynamic modulus at 25 Hz also shows an increase of 25.3%. However, the crack resistance, moisture susceptibility, and drainage capacity at both low temperatures and room temperature exhibited accelerated weakening. When the RPAP content increases to 30%, the reduction in failure strain of regenerated PAC-13 reaches 41.8%, and the reduction in submergence stability reaches 21%. Simultaneously, the water permeability coefficient, void ratio, and interconnected void ratio all demonstrate significant reductions of 23.5%, 6.5%, and 10.0%, respectively, indicating a diminished drainage capacity in the recycled porous pavement mixture. Then again, with the addition of the regenerant, the high-temperature stability of the regenerated porous mixture is reduced by 10.8%, and the mechanical properties are reduced by 6.48%, while the crack resistance at low temperature and room temperature, moisture susceptibility, and drainage ability are enhanced. The verification results of the test section demonstrate the feasibility of utilizing reclaimed asphalt pavement (RAP) material in the porous asphalt mixture. Additionally, it is recommended to select RAP material with a particle size of 4.75 mm or larger while ensuring that the proportion of RAP does not exceed 20%. The research findings of this paper are anticipated to offer guidance for the preparation of PAC-13 reclaimed porous asphalt mixtures while facilitating the recycling and large-scale utilization of old porous pavement materials.