Warm mix asphalt (WMA) is an environmental friendly technology that contributes to the workers safety, reduction of energy consumption and emissions. In this study, the rheological properties of a PG 64-22 asphalt binder blended with Cecabase RT, Rediset, Evotherm, and Sasobit WMA additives are investigated as a function of laboratory aging. Binders modified with WMA additives and the control samples were both aged in the rolling thin film oven (RTFO) at 143°C and at 163°C, respectively. All samples were then long-term aged in an environmental chamber kept at 60°C. The longterm aged samples were collected at different intervals during a six-month period. Rheological data were collected on each aged sample by performing dynamic shear rheometer (DSR) frequency sweep from 25 to 0.1 Hz. at three different temperatures, i.e. 45°C, 60°C, and 76°C. Samples were also evaluated with the Bending Beam Rheometer (BBR) and Fourier-Transform Infrared (FTIR) Spectroscopy. Gauss-Newton method was vii used for non-linear parameter estimation for modeling the relationship of complex modulus (G*) with temperature, frequency, and aging. Regression analysis was also used for modeling BBR creep stiffness and BBR m-value. Although FTIR results show higher oxidation levels for control than all WMA samples, DSR and BBR results show that Sasobit tends to behave closely to control while Cecabase, Evotherm, and Rediset exhibit lower stiffness than both. / text

Economic, environmental and engineering benefits promote the rapid implementation of WMA technologies. However, concerns remain based on changes in the production process that may lead to moisture susceptibility in the early life as compared to HMA. To evaluate WMA moisture susceptibility during this critical period, standard laboratory tests were used for three field projects each with an HMA control mixtures and multiple WMA mixtures. Different specimen types were also evaluated to capture differences in mix design, quality control/quality assurance, and field performance. Specimens were evaluated for moisture susceptibility by Indirect Tensile (IDT) Strength, Resilient Modulus (MR) and Hamburg Wheel-Track Testing (HWTT). Specimens for IDT and MR were tested dry and then tested wet after conditioning as described in AASHTO T283 with one freeze-thaw cycle. HWTT was used to assess both moisture susceptibility and rutting potential under repeated loads in the presence of water at elevated temperatures (i.e., 122°F [50°C]), and the output parameters used for evaluation were the calculated Stripping Inflection Point (SIP) and the rut depth at 5000 load cycles. Based on the results of the laboratory tests performed on PMFC cores acquired at construction and with time, WMA during its early life exhibited inferior moisture resistance when compared to HMA. However, with time, specifically after one summer, the dry and wet properties of WMA became equivalent to those of HMA. For WMA constructed in the fall, the results from this study suggest that the inclusion of recycled asphalt pavement (RAP) or an anti-stripping agent may alleviate possible moisture susceptibility issues in the early life during wet, winter weather conditions. While some laboratory test results demonstrated that WMA is more moisture susceptible than HMA, field performance reported to date from the three projects used in this study shows no evidence of moisture damage. Therefore the search for a laboratory test to screen mixtures for moisture susceptibility continues. An alternative approach, applying Griffith crack growth theory and utilizing IDT, MR and air voids% the adhesive bond energy of asphalt mixtures was calculated for Texas field project. This value holds promise for characterizing performance of asphalt mixtures by considering basic properties and grouping into one representative value.

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.

Warm mix asphalt (WMA) technology has now been successfully used in Ontario for a few years. This shift in usage relates to extensions in construction season, reduced emissions, larger compaction windows, and potential fuel savings. This research between Miller Paving Ltd. and the Centre for Pavement and Transportation Technology attempts to better quantify the difference in hot mix asphalt (HMA) and WMA. The object of this study was three-fold. The first part of the research was to examine the strength characteristics of HMA and WMA as a function of storage time. The purpose of this evaluation was to quantify indirect tensile strength (ITS) and moisture susceptibility of HMA and WMA over time. The second objective involved evaluating the performance characteristics of HMA and WMA. Resilient modulus and dynamic modulus testing were completed on plant-produced HMA and WMA material, which was used to determine long-term performance properties of both mixes. The third and final objective of this study was an economic analysis performed to determine the difference in cost for construction and maintenance for the HMA and WMA pavements. This was completed to determine if the cost of the warm mix technology used in the production of the WMA was offset by fuel savings at the plant. The findings of the research included: • HMA and WMA had statistically equivalent air voids over a four-week storage period. • Dry and wet ITS results for the WMA increased over a four-week storage period while the HMA specimens did not show this same increase. • WMA material had slightly better workability than the HMA material although the values were statistically equivalent. • WMA mix had higher resilient modulus values than the HMA mix. • Dynamic modulus testing showed that at high temperatures, WMA showed to be slightly more susceptible to rutting than the HMA mix, and at lower temperatures, the HMA showed to be slightly more susceptible to fatigue cracking than the WMA mix. • The MEPDG showed that both the HMA and WMA pavements were deemed to be structurally adequate. • An economic analysis of the HMA and WMA pavements compared a life cycle cost analysis over a 20-year design life which included all costs associated with construction, maintenance, and rehabilitation of both the HMA and WMA and showed that the HMA was slightly more cost effective than the WMA. • A field trial was performed by Miller Paving Limited on Highway 62 in Madoc, Ontario showed that the WMA material was more effective at maintaining the temperature of the asphalt mixture during long hauling distances. • Overall the WMA exhibited the same performance properties as the HMA.

Warm mix asphalt (WMA) technology has now been successfully used in Ontario for a few years. This shift in usage relates to extensions in construction season, reduced emissions, larger compaction windows, and potential fuel savings. This research between Miller Paving Ltd. and the Centre for Pavement and Transportation Technology attempts to better quantify the difference in hot mix asphalt (HMA) and WMA. The object of this study was three-fold. The first part of the research was to examine the strength characteristics of HMA and WMA as a function of storage time. The purpose of this evaluation was to quantify indirect tensile strength (ITS) and moisture susceptibility of HMA and WMA over time. The second objective involved evaluating the performance characteristics of HMA and WMA. Resilient modulus and dynamic modulus testing were completed on plant-produced HMA and WMA material, which was used to determine long-term performance properties of both mixes. The third and final objective of this study was an economic analysis performed to determine the difference in cost for construction and maintenance for the HMA and WMA pavements. This was completed to determine if the cost of the warm mix technology used in the production of the WMA was offset by fuel savings at the plant. The findings of the research included: • HMA and WMA had statistically equivalent air voids over a four-week storage period. • Dry and wet ITS results for the WMA increased over a four-week storage period while the HMA specimens did not show this same increase. • WMA material had slightly better workability than the HMA material although the values were statistically equivalent. • WMA mix had higher resilient modulus values than the HMA mix. • Dynamic modulus testing showed that at high temperatures, WMA showed to be slightly more susceptible to rutting than the HMA mix, and at lower temperatures, the HMA showed to be slightly more susceptible to fatigue cracking than the WMA mix. • The MEPDG showed that both the HMA and WMA pavements were deemed to be structurally adequate. • An economic analysis of the HMA and WMA pavements compared a life cycle cost analysis over a 20-year design life which included all costs associated with construction, maintenance, and rehabilitation of both the HMA and WMA and showed that the HMA was slightly more cost effective than the WMA. • A field trial was performed by Miller Paving Limited on Highway 62 in Madoc, Ontario showed that the WMA material was more effective at maintaining the temperature of the asphalt mixture during long hauling distances. • Overall the WMA exhibited the same performance properties as the HMA.

Warm mix asphalt (WMA) represents a group of technologies that allows production of asphalt mixtures at lower temperatures compared to traditional hot mix asphalt (HMA). This results in less fuel consumption and reduction in CO2 ¬and fumes emission. This research was conducted in order to provide North Dakota department of transportation (NDDOT) with a thorough study on state of the practice of WMA in USA and compare WMA performance with HMA. Extensive literature study was conducted, collecting reports and field experiment data from DOTs of states with climate similar to ND. Viewpoints of experts in the field were collected and analyzed using a comprehensive survey. These were added to analysis of collected data on WMA performance. The research results suggest using foaming processes (Double Barrel Green in particular) and chemical additives (Evotherm in particular) at this early stage with guidelines for modifications in WMA specification and testing compared to HMA. / North Dakota Department of Transportation

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.

No description available.

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Hot Mix Asphalt (HMA) plays a large role in the transportation infrastructure and is used to construct highways, runways, parking areas, foot paths and cycle paths. Asphalt is thus being produced in massive amounts around the world. The latest figures on asphalt production indicate that 1.6 trillion metric tonnes of asphalt are produced annually worldwide. This vast quantity of asphalt produced annually has a significant effect on the environment, economy and the surrounding society. According to Mike Acott from the National Asphalt Pavement Association (NAPA) the key strategy to improve HMA is to continuously strive to improve the health safety and environmental practices of HMA. He also emphasises the importance of engaging improvements and innovation in the design and operation phases of HMA as it will result into more health, safety and environmental benefits. (Acott, 2007) It is thus important to improve the sustainability of HMA as it will be used for generations to come. The purpose of this study is to investigate the potential benefits and risks of applying new technology to the current methods of design and construction of asphalt by the South African asphalt industry. The technologies that are investigated in this study are Warm Mix Asphalt (WMA) technology and the use of Reclaimed Asphalt (RA). WMA is asphalt that is designed to be manufactured at a lower temperature than HMA. RA is the use of recycled asphalt material in Hot Mix Asphalt (HMA) thus replacing virgin aggregate and virgin bitumen with recycled components. Both these technologies can have an effect on the sustainability of HMA. This study investigates the benefits and risks of the integration and application of WMA technology and RA into HMA industry in South Africa. The study uses interviews along with environmental and cost analyses to investigate this integration. The findings show that these technologies have definite environmental and cost benefits and that the magnitude of these benefits cannot be ignored. The current use of these technologies is a cause for concern as they are used in limited projects and limited authorities have warmed up to the use of these technologies. The risks involved in using these technologies are caused by a lack of experience and knowledge of these technologies which is aggravated as there are no standard specifications for their use. It is important that the right strategy is put into place to integrate these technologies into the South African asphalt industry in such a way that minimal risk and monetary losses are achieved. / AFRIKAANSE OPSOMMING: HMA speel 'n groot rol in vervoer-infrastruktuur en word gebruik om paaie, aanloopbane, parkeerareas, voet en fiets paaie te bou. Asfalt word dus wêreldwyd in groot hoeveelhede geproduseer. Die nuutste syfers toon dat 1.6 triljoen kubieke meter asfalt jaarliks wêreldwyd geproduseer word. Hierdie groot hoeveelheid asfalt wat geproduseer word het ‘n beduidende effek op die omgewing, ekonomie en die omliggende gemeenskap. Volgens Mike Acott van die Nasionale Asfalt Plaveisel Assosiasie (NAPA) is die voortdurende strewe om die gesondheids, veiligheids en omgewings impakte van HMA te verminder die sleutel-strategie om HMA te verbeter. Hy beklemtoon ook die belangrikheid om verbeterings en innovering in die ontwerp en bedryf fases van HMA aan te bring wat kan lei tot meer veiligheids, gesondheids en omgewings voordele. (Acott, 2007) Dit is dus belangrik om die volhoubaarheid van HMA te verbeter as dit bewaar wil word vir toekomstige geslagte te kom. Die doel van hierdie studie is om die potensiële voordele en risiko's van die gebruik van nuwe tegnologieë op die huidige ontwerp en konstruksie metodes in Suid-Afrika se asfalt bedryf te ondersoek. Die tegnologieë wat in hierdie studie ondersoek word is Warm Mengsel Asfalt (WMA) en die gebruik van Herwonne Asfalt (RA). WMA is asfalt wat ontwerp is om teen ‘n laer temperatuur as konvensionele HMA vervaardig te word. RA is die gebruik van herwinde asfalt in HMA wat lei tot die besparing van nuwe aggregaat en bitumen. Beide hierdie tegnologieë kan 'n invloed op die volhoubaarheid van HMA hê. Hierdie studie ondersoek dus die voordele en risiko's van die integrasie en gebruik van WMA en RA tegnologie in die HMA-industrie in Suid-Afrika. Die studie maak gebruik van onderhoude asook omgewings en koste impak analises om hierdie integrasie te ondersoek. Die bevindinge in die studie toon aan dat hierdie tegnologie definitief voordelig is vir die omgewing en die ekonomie en dat hierdie voordele groot genoeg is om nie geïgnoreer te word nie. Die huidige gebruik van hierdie tegnologieë is 'n rede vir bekommernis, want dit word slegs in ‘n paar projekte aangewend en daar is slegs ‘n paar owerhede wat die tegnologieë ondersteun. Die risiko's wat betrokke is in die gebruik van hierdie tegnologieë word veroorsaak deur 'n gebrek aan ondervinding en kennis van die tegnologieë wat verder vererger word deur die gebrek aan standaard spesifikasies vir die gebruik daarvan.

Recent improvements in warm mix asphalt technologies have spurred an aggressive adoption of these new practices within the asphalt paving industry. Concerns have arisen among federal and state agencies about the effects of this line of products on the performance of asphalt pavements. An investigation of the effects of lowering mixing, aging and compactions temperatures while varying the loose mix aging time was performed. Hamburg Wheel Tracking, Flow Number, Dynamic Modulus and Fracture Energy testing were used to evaluate mechanistic properties of the materials.