Residual moisture from incompletely dried aggregates would most likely remain in the Warm Mix Asphalt (WMA) due to its lower production and compaction temperature, resulting in harmful effects on field performance. Dynamic modulus has been recognized as a parameter that reflects the overall behavior of asphalt mixtures and possesses promising correlations with field performance. This study aims to investigate the effects of moisture susceptibility of WMA on dynamic modulus and simulate the field performance with the aid of Mechanistic-Empirical Pavement Design Guide (MEPDG) software. Four distinct sets of WMA specimens were prepared as follows: 1. fully dried aggregates without moisture conditioning; 2. fully dried aggregates with moisture conditioning; 3. incompletely dried aggregates without moisture conditioning; and 4. incompletely dried aggregates with moisture conditioning. Simple Performance Test (SPT) was employed to collect the raw data of dynamic modulus tests and master curves were constructed from the reduced data using Hirsch model. The results show that moisture can negatively influence the dynamic modulus values and moisture conditioning had more effect than residual moisture from incompletely dried aggregates. Two types of distress, fatigue cracking and rutting, were analyzed in the simulation. Moisture can significantly decrease the resistance against rutting and to a lesser extent, the resistance against fatigue cracking.

Warm-Mix Asphalt (WMA) refers to the asphalt concrete paving material produced and placed at temperatures approximately 50°F lower than those used for Hot-Mix Asphalt (HMA). Economic, environmental and engineering benefits have boosted the use of WMA technology across the world during the past decade. While WMA technology has been successfully utilized as a paving material, several specifications and mix design protocols remain under development. For example, currently, there is no consistent laboratory conditioning procedure for preparing WMA specimens for performance tests, despite being essential for mix performance. Based on previous studies, several candidate conditioning protocols for WMA Laboratory Mixed Laboratory Compacted (LMLC) and off-site Plant Mixed Laboratory Compacted (PMLC) specimens were selected, and their effects on mixture properties were evaluated. Mixture stiffness evaluated in a dry condition using the Resilient Modulus (MR) test (ASTM D-7369) was the main parameter used to select a conditioning protocol to simulate pavement stiffness in its early life. The number of Superpave Gyratory Compactor (SGC) gyrations to get 7±0.5% air voids (AV) was the alternative parameter. Extracted binder stiffness and aggregate orientation of field cores and on-site PMLC specimens were evaluated using the Dynamic Shear Rheometer (DSR) (AASHTO T315) and image analysis techniques, respectively. In addition, mixture stiffness in a wet condition was evaluated using the Hamburg Wheel-Track Test (HWTT) (AASHTO T324) stripping inflection point (SIP) and rutting depth at a certain number of passes. Several conclusions are made based on test results. LMLC specimens conditioned for 2 hours at 240°F (116°C) for WMA and 275°F (135°C) for HMA had similar stiffnesses as cores collected during the early life of field pavements. For off-site PMLC specimens, different conditioning protocols are recommended to simulate stiffnesses of on-site PMLC specimens: reheat to 240°F (116°C) for WMA with additives and reheat to 275°F (135°C) for HMA and foamed WMA. Additionally, binder stiffness, aggregate orientation, and overall AV had significant effects on mixture stiffness. Mixture stiffness results for PMFC cores and on-site PMLC specimens in a wet condition as indicated by HWTT agree with those in a dry condition in MR testing.

"The presence of moisture can lead to serious damage in Hot Mix Asphalt mixes and failures of HMA pavements. This is of an even greater concern for Warm Mix Asphalt (WMA) due to the use of much lower production temperatures which may not be high enough to completely dry the aggregates. In this Maine DOT study, the use of fracture energy parameters was evaluated to determine the influence of incomplete drying of mixes on their mechanical properties. Fracture energy based parameters (ER: energy ratio; RER: ratio of energy ratio) were determined from the following indirect tensile testing on mixes with fully and partially dried aggregates, some of which were subjected to moisture conditioning: Resilient modulus (Mr), creep compliance, and indirect tensile strength (ITS) strength at 5oC. The results indicate that: i. resilient modulus, creep compliance, and indirect tensile strength were all affected by the presence of moisture in mixes; ii. the trend and degree of influence by moisture for the different mechanical parameters are different; iii. The moisture conditioning process has caused larger decreases in resilient modulus and ITS values than incomplete drying of aggregates; however, the same moisture conditioning process has caused much larger decreases in modulus and ITS in asphalt mixes prepared with incompletely dried aggregates than the counterparts prepared with fully dried aggregates; and iv. fracture energy-based parameters (ER and RER) appear to be more distinctive moisture effect/damage indicators than the other parameters. "

Asphalt-rubber mixtures have been shown to have useful properties with respect to distresses observed in asphalt concrete pavements. The most notable change in properties is a large increase in viscosity and improved low-temperature cracking resistance. Warm mix additives can lower production and compaction temperatures. Lower temperatures reduce harmful emissions and lower energy consumption, and thus provide environmental benefits and cut costs. In this study, the effects of crumb rubber modification on various asphalts such as California Valley, Boscan, Alaska North Slope, Laguna and Cold Lake were also studied. The materials used for warm mix modification were obtained from various commercial sources. The RAF binder was produced by Imperial Oil in their Nanticoke, Ontario, refinery on Lake Erie. A second commercial PG 52-34 (hereafter denoted as NER) was obtained/sampled during the construction of a northern Ontario MTO contract. Some regular tests such as Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR), Multiple Stress Creep Recovery (MSCR) and some modified new protocols such as the extended BBR test (LS-308) and the Double-Edge Notched Tension (DENT) test (LS-299) are used to study, the effect of warm mix and a host of other additives on rheological, aging and failure properties. A comparison in the properties of RAF and NER asphalts has also been made as RAF is good quality asphalt and NER is bad quality asphalt. From the studies the effect of additives on chemical and physical hardening tendencies was found to be significant. The asphalt samples tested in this study showed a range of tendencies for chemical and physical hardening. / Thesis (Master, Chemistry) -- Queen's University, 2014-01-30 11:56:43.978

The implementation of warm-mix asphalt (WMA) is becoming more widespread in the United States of America with a growing number of contractors choosing to utilize various WMA technologies. WMA technologies were developed in order to reduce mixing and compaction temperatures of hot mix asphalt (HMA) without affecting the quality of the pavement. Research into the effects of WMA additives suggests that it may be more susceptible to rutting and moisture damage than traditional HMA pavements. The objective of this research is to evaluate the effects of a single WMA additive on resistance to rutting and moisture damage on lab mixed and field mixed pavements. This objective was completed by conducting extensive laboratory experiments to determine and assess the performance of both WMA and HMA mixtures produced using Iowa aggregates. The conclusions of this study are as follow: * Reduced mixing and compaction temperatures were achieved using the selected additive. * The selected WMA additive was successfully used and samples were taken during a local resurfacing project. * Moisture sensitivity of both field mixed WMA and field mixed HMA were comparable although both failed to meet Iowa DOT standards. * Dry Indirect Tensile Strength values of lab mixed WMA and HMA samples were nearly the same. * TSR values of lab mixed HMA surpassed those of lab mixed WMA although both failed to meet Iowa DOT standards. * The aged field mixed HMA successfully passed the Hamburg Wheel Tracker Test and provided the best creep and stripping values compared to all other field mixed specimens. * Lab mixed HMA using a PG 64-22 binder performed the best compared to all other lab mixed specimens although none of the lab mixed specimens successfully passed the Hamburg Wheel Tracker Test.

Reclaimed asphalt pavement (RAP) is a valuable resource that can be recycled into new asphalt mixtures. In recent years, the continued rise of raw material costs has generated considerable interest in increasing RAP usage. Warm mix asphalt (WMA) is a modern development in the asphalt industry that can potentially help increase RAP usage and achieve adequate mixture performance. The purpose of this dissertation is to: 1) develop a method to characterize the absorbed, inert and effective bituminous components in RAP; and 2) evaluate performance of high RAP-WMA mixtures for various pavement applications including airfield surfaces, highway surfaces and highway bases. A unique approach was taken to characterize RAP properties that coupled a dataset of 568 asphalt mix designs spanning five years of practice and testing 100% RAP with added virgin binder; 394 compacted specimens and 68 loose specimens were tested. A method to predict RAP absorbed asphalt was developed and shown to yield more reasonable results than conventional methods which were shown very likely to give incorrect absorbed asphalt contents in some conditions. The relative effectiveness of RAP surface asphalt was evaluated and estimates of inert and effective RAP asphalt were made for a variety of temperature, compactive effort, and warm mix additive conditions. Results showed different behaviors between RAP sources and between hot and warm mix temperatures. These results were also observed in volumetrics of high RAP mixtures. Performance evaluation was based on testing 75 slab specimens and more than 1100 gyratory specimens. Test data indicated a potential for decreased durability as RAP content increases; however 25% RAP highway surface mixtures and 50% RAP base mixtures had similar performance to current practice. Low temperature mixture stiffness testing and thermal cracking analysis indicated slightly increased stiffness with high RAP and 25% RAP highway surface mixtures that had comparable performance to current practice. Dry rut testing indicated high RAP mixtures are rut resistant. Moisture damage testing of high RAP mixtures indicated passing results in tensile strength ratio testing but potential for moisture damage in loaded wheel tracking. Overall, 25% RAP highway surface mixtures are recommended for immediate implementation.

abstract: A recent joint study by Arizona State University and the Arizona Department of Transportation (ADOT) was conducted to evaluate certain Warm Mix Asphalt (WMA) properties in the laboratory. WMA material was taken from an actual ADOT project that involved two WMA sections. The first section used a foamed-based WMA admixture, and the second section used a chemical-based WMA admixture. The rest of the project included control hot mix asphalt (HMA) mixture. The evaluation included testing of field-core specimens and laboratory compacted specimens. The laboratory specimens were compacted at two different temperatures; 270 °F (132 °C) and 310 °F (154 °C). The experimental plan included four laboratory tests: the dynamic modulus (E*), indirect tensile strength (IDT), moisture damage evaluation using AASHTO T-283 test, and the Hamburg Wheel-track Test. The dynamic modulus E* results of the field cores at 70 °F showed similar E* values for control HMA and foaming-based WMA mixtures; the E* values of the chemical-based WMA mixture were relatively higher. IDT test results of the field cores had comparable finding as the E* results. For the laboratory compacted specimens, both E* and IDT results indicated that decreasing the compaction temperatures from 310 °F to 270 °F did not have any negative effect on the material strength for both WMA mixtures; while the control HMA strength was affected to some extent. It was noticed that E* and IDT results of the chemical-based WMA field cores were high; however, the laboratory compacted specimens results didn't show the same tendency. The moisture sensitivity findings from TSR test disagreed with those of Hamburg test; while TSR results indicated relatively low values of about 60% for all three mixtures, Hamburg test results were quite excellent. In general, the results of this study indicated that both WMA mixes can be best evaluated through field compacted mixes/cores; the results of the laboratory compacted specimens were helpful to a certain extent. The dynamic moduli for the field-core specimens were higher than for those compacted in the laboratory. The moisture damage findings indicated that more investigations are needed to evaluate moisture damage susceptibility in field. / Dissertation/Thesis / M.S. Civil and Environmental Engineering 2011

Hot Mix Asphalt (HMA) has been used over the years for laying roads. It required the aggregate and the binder to be heated to temperatures above 160°C (320°F). Heating the aggregate and binder in large quantities consumed a lot of fuel. This called for alternative solutions in the technology of laying roads. This brought about a new technology called Warm Mix Asphalt (WMA). WMA is an emerging technology that can allow asphalt to be produced and compacted at a significantly lower temperature. In the past, a number of researchers evaluated various WMA mixtures using selected testing procedures in the laboratory. However, none of them evaluated all the major WMA products and compared them with WMA mixtures without an additive using a comprehensive set of testing protocols. This paper presents a comprehensive evaluation result of three major WMA additives (Sasobit®, Evotherm J1 and RedisetTM) regarding their viscosity, tensile strength, moisture sensitivity, dynamic modulus and flow number. These three additives were chosen since all of them are prepared from a base wax product. The asphalt showed a decreasing trend in viscosity with increase in the concentration of the additives. The WMA specimen with additives exhibits similar air voids as control WMA specimens which indicate these WMA additives are effective in compacting asphalt mixtures at low temperatures. The Indirect Tensile Strengths (ITS) and Tensile Strength Ratio (TSR) values of the WMA specimen with admixtures were found to be higher than the control WMA specimens. This result indicates that the admixtures play a significant role in enhancing the properties of WMA. WMA mixtures with additives exhibited higher dynamic modulus than the control WMA at all temperatures. All the specimens passed the requirement of 10,000 cycles of repeated loading. The WMA specimen with Sasobit® additive exhibited the lowest permanent deformation. Based on overall test results it can be concluded that Sasobit®, Evotherm J1 and RedisetTM WMA additives are effective in producing WMA mixtures in the laboratory which have high strengths.

This thesis aims to contribute to the growing body of warm mix asphalt (WMA) research by evaluating the differences in behavioral properties of three WMA mixtures, representing the three warm mix technology (WMT) categories (foaming, chemical additives, and organic waxes), relative to a control hot mix asphalt (HMA) in a specific set of conditions which is not well documented in literature. These conditions are: plant produced mixtures with all virgin aggregates and binder (i.e. no recycled materials) and no additives other than the warm mix technology. These mixtures were evaluated at low, intermediate, and high testing temperatures before and after a set of conditioning protocols (CPs), which utilized varying levels of isolated and combined oxidative, moisture, and freeze-thaw damage. A key feature of this thesis is that damage induced by these CPs has been benchmarked relative to measured field aging effects through studies which evaluated the three WMA mixtures and one HMA mixture used to obtain the results presented here, along with additional mixtures not considered in this thesis.

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