Performance Of Warm Mix Asphalt Research Articles

A probabilistic investigation of long-term field performance of warm mix asphalt pavements

Warm-mix asphalt (WMA) has been gaining popularity in sustainable road engineering due to its reduced environmental impacts. However, uncertainties remain regarding its long-term pavement performance compared to hot mix asphalt (HMA). Especially, the critical factors influencing the field performance of WMA are yet to be determined. Hence, this study analyzes the long-term field performance of pavement overlaid with WMA, using data from the Specific Pavement Studies 10 (SPS-10) of the long-term pavement performance (LTPP) program. The evaluation includes 58 field sections from nine projects across the United States, encompassing two WMA types (foaming processing and chemical additive) and their corresponding HMA control sections. Performance indicators such as alligator cracking, longitudinal cracking in the wheel path, transverse cracking, rutting, and roughness (measured by the international roughness index, IRI) were considered. Per-state and per-climate region Bayesian multilevel models were built to account for site- and region-level heterogeneity. The study results demonstrated that pavement with WMA performed equally well to the HMA counterparts under similar conditions, indicating that their potential for widespread application in meeting both performance standards and environmental conservation requirements. Also, WMA technologies did not differ in pavement performance, and thus the field performance of WMA was not a dominant factor in deciding WMA technology types. Furthermore, Bayesian multilevel models proved highly effective in performance data varying across construction sites and regions.

Comparative assessment of hot and warm mix asphalt to develop a sustainable pavement: Kg Ayer Merah Mersing case study

Abstract In this study, the construction and pavement properties of warm mix asphalt (WMA) in rural areas were examined in comparison with the conventional mixture of hot mix asphalt (HMA). Both WMA and HMA mixtures were constructed at Kg Ayer Merah, Mersing, Johor in accordance with Public Work Department specifications, regarding redesign of road pavements in rural areas. This study to evaluate the comparison performance of WMA and HMA mixtures at one month and four months after construction based on performance in mechanical (Rate of cooling, density, Marshall, resilient modulus and dynamic creep) and macrotexture performance (sand patch and pendulum test value) and environmental analysis (carbon emission). The findings showed that WMA mixtures showed similar and better performance over HMA mixtures after four months construction in mechanical performance. WMA also obtained a higher rate of cooling than HMA besides reducing carbon emissions during production and road construction indicating the mixture more convenient to cater for double handling in rural areas. This huge impact is in line with the sustainable development goals (SDGs), which aim to develop sustainable infrastructure and reduce global warming issues.

Waste motor engine oil – the influence in warm mix asphalt

Employing Hot Mix Asphalt (HMA) technology for asphalt pavement construction results in the emission of greenhouse gases and other harmful pollutants, contributing to significant air pollution due to extensive energy consumption. Consequently, the adoption of Warm Mix Asphalt (WMA) is recommended, given its potential for enhanced energy efficiency and reduced emissions due to lower mixing and production temperatures compared to HMA. This research delves into the impact of incorporating waste motor engine oil (WMEO) as a bitumen modifier in warm mix asphalt. The investigation involved adding WMEO at various percentages, specifically 0%, 3%, 4%, and 5% based on the weight of bitumen. The study assessed the performance of the samples in terms of penetration, softening point, stability, flow, and stiffness. The findings revealed that the incorporation of WMEO in warm mix asphalt led to a substantial improvement in penetration and softening point. Moreover, the results indicated that incorporating WMEO as a bitumen modifier could enhance the performance of WMA in terms of stability, flow, and stiffness.

Characterization of aged bitumen recovered from in-situ polymer-modified HMA and WMA using advanced technologies

The growing attention of public opinion towards the environment has prompted, in the last decades, to find eco-sustainable and economic alternatives to the traditional productions of hot-mix asphalt (HMA). Under these auspices, the use of warm mix asphalt (WMA) technology applied to mixtures containing reclaimed asphalt (RA) has grown, also due to the well-proven advantages in terms of plant odor emissions and improved working conditions. In addition, it is now known that the mechanical performance of WMAs is completely comparable, even superior in some cases, to that of HMAs. However, to date, there is no comparison in terms of long-term performance of bitumens used in full-scale pavements laid with the two different technologies. Therefore, the aim of this research is to evaluate the oxidative and rheological state of four bitumens recovered from different layers of a full-scale pavement prepared with WMA and HMA technologies and set up a methodology tool set for investigating the physicochemical properties of bitumens. An in-depth laboratory investigation, carried out through physicochemical and rheological tests, has shown that the bitumens used in WMA mixtures are characterized by less oxidation than HMA ones (which are characterized by longer relaxation and glass transition times) and the Styrene-Butadiene-Styrene (SBS) polymers inside them are less degraded and still contribute positively to the rheological response even after five years in service, demonstrating the ability of the chemical additive to act as possible “sacrificial agent”, safeguarding the rheological characteristics of polymer modified bitumens (PMBs).

Suitability of warm mix asphalt (WMA) technologies based on performance and energy consumption

Studying the effects of material variability on the performance of warm mix asphalt (WMA) is important to understand the benefits of reduced production temperatures. This study compares the performance of five different WMA mixtures prepared with two varying base binders and two different aggregate sources. The rutting, fatigue, and moisture sensitivity of asphalt mixtures were evaluated using cyclic compression test, indirect tensile cracking test, and modified Lottman test, respectively. Additionally, a theoretical analysis was used to compare the energy consumption during the production process. The results indicated that the performance of WMA is a function of the type of the base binder, aggregate source, and the type of WMA technology. Nonetheless, all the WMA mixtures contributed to higher energy savings in comparison to hot mix asphalt (HMA). Based on the ranking framework used in this study, the use of Rediset is recommended to achieve adequate performance and lower energy consumption.

Investigating the Effect of Experimental Factors on the Performance of Warm Mix Asphalt with Wax Additive using Application of the Taguchi Method

The objective of this study was to assess the impact of experimental factors on the volumetric properties and performance of warm mix asphalt (WMA) with RH-WMA using the Taguchi method. The gradations of the mixtures were based on AC 14, as specified by the Public Works Department of Malaysia. An L16 orthogonal array was employed to design the mixtures, considering three factors: compaction temperatures ranging from 95 to 140°C, RH-WMA contents ranging from 1% to 4%, and asphalt contents ranging from 3.5% to 6.5%. Sixteen mixtures were prepared according to the L16 array. The study focused on investigating several volumetric properties, including bulk-specific gravity, air voids, voids filled with asphalt, and voids in mineral aggregates. Additionally, the strength behavior of the samples was analyzed using the Taguchi method. The resilient modulus and performance of the mixtures were also evaluated. The results of the study indicate that a high RH-WMA content led to a slight decrease in the strength of the asphalt mixture and air voids. However, it increased the voids filled with asphalt (VFA) and resulted in softening of the asphalt mixtures.

Evaluating the use of different fillers and Kaowax additive in warm mix asphalt mixtures

The existing concerns about the global warming have prompted many researchers to study the warm mix asphalt (WMA) mixtures. Although WMA enjoys several advantages over the hot mix asphalt (HMA), it suffers from certain flaws such as moisture susceptibility and low temperature cracking. Therefore, it is important to enhance the performance of WMA, and one way of doing it is to use suitable fillers in the asphalt mixtures. The study aim is to evaluate the impact of the Portland cement type-II, fly ash, and the calcium carbonate as filler, on the WMA performance that made with Kaowax additive. We performed the semi-circular bending (SCB) test at low temperature, the four-point bending fatigue test, the indirect tensile strength (ITS), resilient modulus tests at medium temperature, and the dynamic creep test at high temperature. According to the obtained results, the presence of Kaowax increased resilient modulus and the rutting strength of the asphalt mix. The WMA samples containing the fly ash filler had good moisture susceptibility. The use of cement filler in the WMA resulted in improved rutting resistance. The calcium carbonate filler increased the performance of the WMA mixtures at all temperatures.

Feasibility assessment of palmitamide derived from waste edible oil as a warm mix asphalt additive

The disposal of waste edible oil (WEO) has become a global challenge with both environmental and economic issues. To provide a novel strategy for the refinement recycling of WEO, this work investigated the feasibility of palmitamide derived from WEO as a warm mix asphalt (WMA) additive. The molecular structure and thermodynamic characteristics of palmitamide were first determined. Following, WMA binders with different palmitamide contents were prepared and their temperature sensitivity and rheological properties were evaluated. Additionally, the engineering performance of WMA mixtures was explored and the environmental benefits of WEO-derived palmitamide were assessed using the gas chromatography-mass spectrometry. The results demonstrate that the phase transition temperature of WEO-derived palmitamide is 98.87 °C, which shows great potential as a WMA additive. Palmitamide provides asphalt workability suitable for construction at relatively low temperatures through reducing the flow activation energy of asphalt. In addition, the moisture damage resistance and deformation resistance of WMA is also improved due to the hydrophobicity and filling effect of palmitamide, respectively. While it is inevitable that palmitamide slightly weakens the fatigue and low-temperature performance of WMA. Moreover, the application of WEO-derived palmitamide can reduce the volatile organic compounds of asphalt in the mixing stage and compaction stage by 40.3% and 30.8%, respectively. The findings contribute to the sustainable development of road engineering and the circular of waste resources.

The Effect of Rubber Crumbs on Marshall Properties for Warm Mix Asphalt

A new pavement technology has been developed in Highway engineering: asphalt pavement production is less susceptible to oxidation and the consequent damages. The warm mix asphalt (WMA) is produced at a temperature of about (10-40) oC lower than the hot asphalt paving. This is done using one of the methods of producing a WMA. Although WMA's performance is rather good, according to previous studies, as it is less susceptible to oxidation, it is possible to modify some of its properties using different materials, including polymers. Waste tires of vehicles are one of the types of polymers because of their flexible properties. The production of HMA, WMA, and WMA modified with proportions of (1, 1.5, and 2%) of rubber crumbs by the dry method are accomplished in this work. Marshall Test and volumetric properties determination are performed to evaluate its performance. The results showed that using 1% of rubber crumbs as a replacement for fine aggregate in the warm asphalt mixture produced the best properties of the WMA compared to the conventional WMA.

Nanoscale study on adhesion performance and aging degree prediction of warm mix asphalt under UV aging condition

Compared with hot mix asphalt, warm mix asphalt ( WMA) has inferior adhesion performance, and ultraviolet (UV) aging will further weaken the adhesion performance of WMA. There are, however, few investigations on the aging mechanism under conditions of single UV radiation, and the majority of current research on UV aging is conducted under the combined action of UV radiation and oxygen. In this paper, an indoor accelerated experimental equipment for UV aging was developed, and two experimental schemes of oxygen isolation condition and light-oxygen coupling condition were designed. The developed UV aging tests were carried out on WMA this for 0–50–100–150 and 200 h. The nano adhesion properties were studied by atomic force microscopy ( AFM) and gel permeation chromatography ( GPC) experiments. The characterization method of WMA nano adhesion performance was proposed using correlation analysis. In addition, the nonlinear differential equations between nano-indexes and aging time were established by the Verhulst model. The results showed that the generation of microcracks and the increase of large molecular weight during UV aging will decrease WMA adhesion performance, and the degradation is more significant under the light-oxygen coupling conditions. Moreover, the correlation coefficients between large molecular weight and nano-adhesion under two UV aging conditions were higher than 0.90, showing that large molecular weight could characterize the degradation of nano-adhesion of WMA after UV aging. The saturation characteristics of the honeycomb structure area ratio were prominent, and the coefficient of determination of the nonlinear equations were higher than 0.93 for both two UV aging conditions. The aging model can be used to accurately characterize and predict the WMA UV aging state through the variation of honeycomb structure area ratio.

WMA Overlay Optimization Based on the LTPP Database: Using the RSM Method

This study investigates the field performance of Warm Mix Asphalt (WMA) road overlays containing various amounts of RAP and binder. Rutting, the International Roughness Index (IRI), and transverse, longitudinal and alligator cracking are the key parameters considered here. Our research is based on a Specific Pavement Study-10 experiment (SPS-10) conducted in nine states of North America (eight in the USA and one in Canada) that included 31 road sections in dry and wet regions. Road overlays were evaluated 1 and 4 years after their placement in terms of anti-cracking behavior and were compared with the pre-treatment status of the road. The best rutting resistance occurred at 15% and 12% RAP in dry and wet regions, respectively. For IRI, 30% and 0.0% RAP were the best for dry and wet regions as well. The maximum longitudinal crack recovery rates were found at site 3 (BA01, Arizona; dry region) and site 26 (AA65, Missouri; wet region), with RAP contents of 20% and 36%, respectively. In addition, alligator cracking did not occur post-overlay, so optimal RAP and binder contents cannot be suggested. The greatest improvements were found at site 15 (AA01, Washington state; dry) and site 30 (AA63, Oklahoma; wet). The response surface method (RSM) was also developed to explore the optimal models for RAP and selection of binder contents to minimize the rutting, IRI, and transverse and longitudinal crack lengths.

Laboratory and Field Performance Evaluation of Warm Mix Asphalt Incorporating RAP and RAS

Pavement sustainability draws attention from different stakeholders in recent years. Warm mix asphalt (WMA) incorporating reclaimed asphalt pavement (RAP) or reclaimed asphalt shingles (RAS) has been widely recognized as a sustainable combo for pavement construction by conserving natural resources and reducing greenhouse gas emission. However, as their usage surges, little research has been conducted to date through a comprehensive laboratory and field evaluation to verify the performance of WMA incorporating RAP and RAS compared to traditional hot mix asphalt (HMA). In this research, five WMA sections with different WMA techniques and one control HMA section constructed in Oklahoma were continuously monitored for four years. The aggregate consensus, source, and gradation properties were tested in the laboratory. Mixture characteristics for lab-compacted samples including cracking resistance, rutting performance, moisture susceptibility, and water permeability were measured to compare WMA to HMA incorporating RAP and RAS. In addition, pavement surface conditions in terms of pavement cracking, rutting, roughness, texture, and friction were collected from the field site ten times in four years by using several state-of-the-art high-speed devices without traffic control. The laboratory and four-years field monitoring results demonstrate that WMA incorporating RAP and RAS accomplishes desired performance while providing sustainable benefits.

Performance Evaluation of Fatigue and Fracture Resistance of WMA Containing High Percentages of RAP

Sustainability and durability are the key requirements of pavement structure. Sustainability of asphalt pavement structure involves utilization of Warm Mix Asphalt (WMA) technologies with the addition of Reclaimed Asphalt Pavement (RAP), where durability of asphalt involves performance parameters like fatigue and fracture resistance properties etc. Utilizing the RAP content in asphalt mix increases the mixing and compaction temperature which may degrade the performance of asphalt. Hence, numerous studies have recommended different WMA technologies to decrease mixing and compaction temperature of asphalt mix containing RAP. The present research work evaluates the fatigue and fracture performance of WMA and Hot Mix Asphalt (HMA) with varying percentages of RAP and Sasobit. Different mixes of WMA and HMA were designed with varying percentages of RAP (0, 20, 40 and 60%) through Marshall Mix design. Sasobit (organic/wax-based additive) was used as WMA technology to prepare WMA at varying percentages (0, 2, 4 and 6%). The fatigue behavior of asphalt was evaluated using four-point bending test, where fracture resistance of asphalt was determined using Semi Circular Bending (SCB) test in the laboratory. Fatigue and fracture resistance of WMA were improved with the increase in percentages of Sasobit and RAP content, while the addition of RAP in HMA showed a decreasing trend of fatigue and fracture resistance due to the stiffer nature of RAP. Furthermore, WMA was identified as economical for construction besides other benefits like improved properties and environment friendly asphalt mix. Doi: 10.28991/cej-2021-03091741 Full Text: PDF

Performance Evaluation of Warm Asphalt Mixtures Containing Chemical Additive and Effect of Incorporating High Reclaimed Asphalt Content.

Reclaimed asphalt (RA) and Warm mix asphalt (WMA) are two widely used environmentally friendly mixtures in the paving industry. This study compares the laboratory performance of conventional hot mix asphalt (HMA) with virgin WMA, and WMA containing 60% RA content, using thermal stress restrained specimen test, wheel tracking test, and indirect tensile strength test. Based on test results, a reduction of 15 °C in mixing temperature was achieved for WMA mixtures compared to HMA using the given chemical additive. The virgin WMA mixture showed superior cracking resistance but lower rutting resistance than HMA, and incorporation of RA material without any further modification in the binder, deteriorated both cracking and rutting performance of WMA. It was also shown that laboratory short-term aging can significantly affect the performance of the mixtures.

Rutting and moisture-induced damage potential of foamed warm mix asphalt (WMA) containing RAP

Despite significant economic and environmental benefits, performance of warm mix asphalt (WMA) containing reclaimed asphalt pavement (RAP) remains a matter of concern. Among the current WMA technologies, the plant foaming technique (called “foamed WMA” in this study) has gained the most attention, since it eliminates the need for chemical additives. In the present study, the laboratory performance, namely rutting and moisture-induced damage potential of foamed WMA containing RAP were evaluated and compared with those of similar hot mix asphalt (HMA) containing identical amount of RAP. Dynamic modulus, Hamburg wheel tracking (HWT) and flow number tests were performed to assess the rutting resistance of the mixes. Also, stripping inflection point from HWT tests and tensile strength ratio after AASHTO T 283 and moisture induced sensitivity test (MIST) conditioning were used to evaluate the moisture-induced damage of asphalt mixes. It was found that MIST conditioning effectively simulates the moisture-induced damage and can capture the propensity of asphalt mixes to moisture damage more distinctly compared to AASHTO T 283 method due to application of cyclic loadings. The foamed WMA was found to exhibit higher rutting and moisture-induced damage potential due to lower mixing and compaction temperatures compared to HMA. However, the increase in RAP content was found to reduce rutting and moisture-induced damage potential for WMA. Therefore, the lower stiffness of foamed WMA may be compensated with the addition of stiffer binder from RAP.

Characteristics of Warm Mix Asphalt Incorporating Coarse Steel Slag Aggregates

The major goal of sustainable practices is to preserve raw resources through the utilization of waste materials as an alternative to natural resources. Decreasing the temperature required to produce asphalt mixes contributes to environmental sustainability by reducing energy consumption and toxic emissions. In this study, warm mix asphalt incorporating coarse steel slag aggregates was investigated. Warm mix asphalt was produced at different temperatures lower than the control asphalt mixes (hot mix asphalt) by 10, 20, and 30 °C. The performances of the control and warm mix asphalt were assessed through laboratory tests examining stiffness modulus, dynamic creep, and moisture sensitivity. Furthermore, a response surface methodology (RSM) was conducted by means of DESIGN EXPERT 11 to develop prediction models for the performance of warm mix asphalt. The findings of this study illustrate that producing warm mix asphalt at a temperature 10 °C lower than that of hot mix asphalt exhibited the best results, compared to the other mixes. Additionally, the warm mix asphalt produced at 30 °C lower than the hot mix asphalt exhibited comparable performance to the hot mix asphalt. However, as the production temperature increases, the performance of the warm mix asphalt improves.

Comparative Performance of Different Warm Mix Asphalt Technologies under the Influence of High Aircraft Tire Pressure and Temperature

Warm mix asphalt (WMA) technologies allow the production and placement of asphalt concrete materials at a lower temperature than the traditional hot mix asphalt (HMA). These materials simultaneously reduce the production fuel costs, increase the available hauling distance, lengthen the paving season, are eco-friendly, and ensure safer working conditions. Airport authorities can use such materials for construction applications to minimize the downtime and user-delay costs. However, the existing Federal Aviation Administration (FAA) construction specifications do not provide guidance on the implementation of such technologies, especially under the conditions created by aircraft with high tire pressure. To this end, the FAA National Airport Pavement and Materials Research Center (NAPMRC) conducted accelerated pavement tests as part of Test Cycle 1 (TC-1) to study the application potential of WMA (using chemical additive) on airport pavements. TC-1 results showed WMA performance was comparable to P-401 HMA performance in rutting. Test Cycle 2 (TC-2) study investigated the rutting performance of chemical, organic, and hybrid additive-based warm mixes alongside an FAA specification P-401 HMA counterpart. Four different test lanes were constructed accordingly in the outdoor area of NAPMRC, each encompassing three different test sections. Using the sixth-generation airport heavy vehicle simulator (HVS-A), sections on the north side of the test lanes were trafficked with 61.3 kips (272.7 kN) moving wheel load at a controlled temperature of 120°F (48.9°C). The chemical additive-based warm mix appeared to exhibit comparable performance to the HMA. A laboratory characterization effort also seemed to corroborate the rutting observations from traffic tests.

Performance comparison of warm mix asphalt for plateau area

The warm mix asphalt (WMA) technology is commonly applied for highway pavements in high-altitude plateau regions in China, where extreme weather conditions are common. The study is to evaluate the performance of WMA with different additives in the areas. The tests show that all the additives could reduce the viscosity of asphalt binder to reduce the mixing and compacting temperature of asphalt mixture. The solid additives could also decrease the penetration and ductility value, and increase the softening point and the PG high temperature of asphalt binder; therefore, are suitable for improving the high-temperature performance of WMA in the high-temperature regions. However, the surface-active liquid additives are suitable in the plateau areas in low-temperature conditions. The lab data for the Ya-Kang highway pavement to Tibet Plateau show it is suitable to control the mixing temperature at about 20°C lower than the normal hot mix asphalt during the construction period.

The Role of Additives in Warm Mix Asphalt Technology: An Insight into Their Mechanisms of Improving an Emerging Technology.

The asphalt industry’s incentive to reduce greenhouse gas emissions has increased since the 1990s due to growing concerns on environmental issues such as global warming and carbon footprint. This has stimulated the introduction of Warm Mix Asphalt (WMA) and its technologies which serve the purpose of reducing greenhouse gas emissions by reducing the mixing and compaction temperatures of asphalt mix. WMA gained popularity due to the environmental benefit it offers without compromising the properties, performance and quality of the asphalt mix. WMA is produced at significantly lower temperatures (slightly above 100 °C) and thus results in less energy consumption, fewer emissions, reduced ageing, lower mixing and compaction temperatures, cool weather paving and better workability of the mix. The latter of these benefits is attributed to the incorporation of additives into WMA. These additives can also confer even better performance of WMA in comparison to conventional Hot Mix Asphalt (HMA) methods. Even though there are recommended dosages of several WMA additives, there is no general standardized mixture design procedure and this makes it challenging to characterize the mechanism(s) of action of these additives in the warm mix. The effects of the addition of additives into WMA are known to a reasonable extent but not so much is known about the underlying interactions and phenomena which bring about the mechanism(s) by which these additives confer beneficial features into the warm mix. Additives in a certain way are being used to bridge the gap and minimize or even nullify the effect of the mixing temperature deficit involved in WMA processes while improving the general properties of the mix. This review presents WMA technologies such as wax, chemical additives and foaming processes and the mechanisms by which they function to confer desired characteristics and improve the durability of the mix. Hybrid techniques are also briefly mentioned in this paper in addition to a detailed description of the specific modes of action of popular WMA technologies such as Sasobit, Evotherm and Advera. This paper highlights the environmental and technical advantages of WMA over the conventional HMA methods and also comprehensively analyzes the mechanism(s) of action of additives in conferring desirable characteristics on WMA, which ultimately improves its durability.

Investigation of aggregate moisture content variation and its impact on pavement performance of WMA

For warm mix asphalt (WMA), aggregates cannot be completely dried due to the low heating temperature, which further adversely affects the pavement performance. This study aimed to (1) analyze the effect of particle size, heating temperature and heating time on the variation in the moisture content in aggregates, (2) compare the interaction ability between warm mix asphalt binders and aggregates with different moisture contents from a rheological perspective and (3) to study the effect of aggregate moisture contents on the pavement performance of WMA. Results show that the quadratic function can be used to express the decline in moisture content over time. The decline rate of moisture content increases with the decrease in particle size. The moisture content of fine aggregate dominates that of the whole aggregate system. The decline rate of moisture content exhibits strong temperature sensitivity in the heating temperature ranging from 110 °C to 150 °C. The sensitivities of different evaluation parameters of the asphalt-aggregate interaction were compared by sensitivity analysis. With the decrease in the moisture content of aggregates, the pavement performance of WMA can be improved. These findings provide understanding on the variation in aggregate moisture content during the heating process, and prove that reducing aggregate moisture content can improve the pavement performance of WMA.