Warm Mix Asphalt Binders Research Articles

Effects of Laboratory Ageing on the Chemical Composition and High-Temperature Performance of Warm Mix Asphalt Binders

Warm asphalt mixtures can suffer from decreased short-term high-temperature performance; therefore, introducing additional modifiers can mitigate this risk. This study investigates the effects of a liquid organosilane warm mix additive (WMAd) and grade-bumping polyethylene-based additive added simultaneously to asphalt binders on their chemical composition and its relationship with performance characteristics. Previous studies found relationships between the formation of certain chemical species during bitumen ageing and the increase in their viscosity, stiffness and other performance characteristics—the present work intended to verify these relationships when the two mentioned additives are used. Two asphalt binders were investigated—a paving-grade 50/70 binder and a 45/80-55 polymer-modified bitumen. The chemical analysis was performed using Fourier-transform infrared (FTIR) spectroscopy in attenuated total reflectance mode and focused on the quantification of carbonyl, sulfoxide, polybutadiene and polystyrene structures in the asphalt binders subjected to laboratory short- and long-term ageing. Additionally, the relationships between asphalt binder performance and selected FTIR indices were evaluated using a dynamic shear rheometer. It was found that the investigated additives significantly affected the apparent contents of all evaluated chemical structures in the asphalt binders; however, these changes were not reflected in their performance evaluation.

Full extraction of asbuton bitumen for binder replacement in warm mix asphalt

Abstract Asbuton can be utilized as an optional binder in asphalt mixture by semi-extraction or full extraction. Full extraction of asbuton by using solvent can maximize the content of bitumen while discarding the mineral. However, different solvent content influenced the asbuton bitumen properties. Thus, this study evaluated the effect of different percentages of toluene solvent on the full extraction. Four different percentages of solvent content 1 to 4 % of toluene were used in this study. The asbuton bitumen was then tested for penetration, softening point, flash point, specific gravity, and thin film oven test. The asbuton bitumen was then used to design warm mix asphalt (WMA). Based on the Marshall mix design, the optimum bitumen content (OBC) is 6.25 %. The WMA with full extraction asbuton bitumen fulfilled the Marshall requirement by stability of 1374 kg, and 96.97% retained stability. It also produced 3.57 mm flow with 3.46 % void in mix, 15.08 % void mineral aggregatte, and 76.41 of void filled bitumen. As a result, it is discovered that full extraction asbuton can serving as the WMA binder replacement.

Using tribological approach to assess production temperatures of asphalt binders

In this study, ball on three plates (BOTP) experiment has been used to propose an approach for evaluating the mixing and compaction temperatures of asphalt binder. The results are compared and correlated with equi-viscous- and workability- based methods to arrive at the proposed criterion. A viscosity grade binder, VG30, was modified with varying dosages of Sasobit and Rediset, and the study was executed considering two different types of aggregates (Granite and Dolerite). It was found that warm mix asphalt (WMA) binders can reduce the production temperatures of VG30, irrespective of the test methodology. Equi-viscous method was found to be inappropriate in the quantification of the production temperatures of WMA binders. Workability test results indicated that reduction in mixing and compaction temperatures is a function of the type of warm mix additive, dosages used, and aggregate source. Based on the variability of test parameters in BOTP test, a normal load of “1 N” and a sliding speed of “0.3 m/s” were found to give consistent results of coefficient of friction (CoF). The effect of plate type (Granite, Dolerite, and steel) on the values of CoF was found to be insignificant, and the use of steel plates was recommended. The results of BOTP and workability were in good agreement with each other. Temperature ranges corresponding to the CoF of “0.255–0.282” and “0.317–0.350” are proposed for assessing the mixing and compaction temperatures, respectively.

The Combined Effects of Additives on the Conventional and High-Temperature Performance Properties of Warm Mix Asphalt Binders.

The present study investigates the effects of the simultaneous use of two additives, an organosilane warm mix asphalt (WMA) agent and a grade-bumping polyolefin compound, on the conventional and high-temperature performance properties of a paving grade 50/70 bitumen and a polymer-modified 45/80-55 bitumen. The WMA agent and polyolefin additive were introduced to the binders at rates of up to 0.3% and 2%, respectively. The base asphalt binders and their blends with the additives were tested before and after aging in a rolling thin film oven test at a temperature of 143 °C. The effects of the investigated additives were found to be dependent on the type of base binder and its aging state. It was generally observed that the WMA additive decreased the performance of the asphalt binders and limited the effects of the other additive, which increased the high-temperature stiffness and non-recoverable compliance of the blends. This interaction amounted to as much as an approx. 20% decrease in high-temperature stiffness and non-recoverable compliance of the binders. The additives caused a small increase in the elasticity of the binders and improved their creep performance when measured in multiple stress creep recovery tests.

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.

Understanding the moisture sensitivity of warm-mix asphalt binders based on bond strength

Moisture damage in asphalt mixtures is typically attributed to the loss of bond strength at the interface of the asphalt binder and aggregate matrix. Selecting an appropriate combination of materials that resist moisture-induced damage is therefore critical. This concern is of utmost importance when asphalt mixtures are prepared at lower temperatures (i.e. warm-mix asphalt (WMA) mixtures). An attempt was thus made to quantify the impact of moisture on asphalt mixtures prepared using four different WMA additives and two aggregates through bond strength tests. The results showed that WMA binders imparted similar or even higher bond strength than the base asphalt binder, regardless of the aggregate source and moisture exposure (wet or dry). The use of WMA additives improved the moisture sensitivity (evaluated through the bond strength ratio), despite lower production temperatures, compared with the base asphalt binder (VG30). Statistical analysis showed that the asphalt binder type significantly affected the bonding mechanism and moisture sensitivity. Based on the ranking protocol used in this study, use of the chemical-based WMA additive Rediset showed the best performance compared with other WMA additives in VG30.

Exploring the consequences of reduced aging on the performance of warm mix asphalt binders

ABSTRACT Warm mix asphalt (WMA) technology has proven to be a viable alternative to asphalt pavement production due to its lower mixing and compaction temperatures. However, the performance of asphalt binders is a concern linked to WMA technology due to its reduced aging effect. This study investigates the impact of redcued aging temperature on the performance of two different WMA additives blended with VG30 binder. Fourier transform infrared spectroscopy (FTIR) was performed to check changes in chemical composition of asphalt binder due to aging. Performance of the WM modified asphalt binders was assessed using linear amplitude sweep (LAS), multiple stress creep and recovery (MSCR), and bitumen bond strength (BBS) tests. FTIR analysis showed that used WMA additives increases the aging resistance of asphalt binder. Test results revealed that the application of Rediset enhanced the fatigue performance compared to neat and Sasobit modified asphalt binder. On the other hand, Sasobit decreased the non-recoverable creep compliance (Jnr) and increased the percent recovery (%R), whereas the contrary trend was observed with the addition of Rediset. It was found that Rediset exhibits the antistripping properties thereby improving the bond between asphalt binder and the aggregate, even at reduced production temperature.

A novel method for determining the wax precipitation temperature in wax-based warm mix asphalt

ABSTRACT To accurately determine the wax precipitation temperature (WPT) of wax-based warm mix asphalt binder, a novel algorithm for WPT calculation was proposed, and the process of wax precipitation in asphalt, as well as the effects of aging, cooling rate, and shear rate on wax precipitation characteristics, were investigated through dynamic shear rheometer (DSR) tests and polarised light microscopy (PLM) experiments. The research findings reveal the following: The refined WPT algorithm exhibits heightened precision compared to the traditional viscosity method, showcasing superior reproducibility and mitigating human-induced errors. During the cooling process, wax molecules become oversaturated, leading to the precipitation of wax crystals and the transformation of asphalt into a solid–liquid two-phase system. The aging of asphalt causes changes in its composition, shifting the phase equilibrium towards favouring wax precipitation. The WPT of asphalt is also influenced by the cooling rate and shear rate, and a larger cooling rate and shear rate will reduce the WPT. Wax crystals are less numerous and more regular in shape at low cooling rates.

Warm Mix Asphalt Binder Utilizing Water Foaming and Fluxing Using Bio-Derived Agent.

The present paper investigates the effects of simultaneous mechanical foaming using water and fluxing with a bio-derived agent on the properties of three distinct asphalt binders: 50/70 paving-grade bitumen, 45/80-55 polymer-modified bitumen, and 45/80-80 highly modified asphalt binder. The testing involved classical tests for assessing binder consistency (penetration at 25 °C, ring and ball softening point, Fraass breaking point, and dynamic viscosity) as well as performance tests (high and low Superpave critical temperatures and multiple stress creep recovery). The tests included assessment directly after asphalt binder foaming and were repeated after a 14-day period. It was shown that bitumen foaming had only short-term effects on the asphalt binders, which did not persist in the repeated tests after 14 days. The fluxing agent that was utilized caused significant changes in the consistency of all asphalt binders. The changes in the performance characteristics of the 50/70 and 45/80-55 binders were severe and amounted to a significant decrease in high-temperature performance of these binders. On the other hand, an improvement in all performance characteristics in the case of the 45/80-80 asphalt binder was observed as a result of the applied processes, particularly when measured 14 days after foaming. This study shows that the simultaneous use of foaming and the fluxing additive decreased the dynamic viscosity of the 45/80-80 binder, while improving its properties relating the pavement performance.

Physical, Chemical and Thermal Properties of Palm Oil Boiler Ash/Rediset-Modified Asphalt Binder

The growth of the palm oil industry has resulted in an increase in the production of solid waste, created from the extraction of fresh fruit bunches, which can take the form of palm oil boiler ash (POBA). POBA can be used to modify asphalt binder and asphalt mixtures to reduce the harmful effect of this waste on the environment. The objective of each modification is to increase the strength, stiffness, durability, workability and constructability of asphalt mixtures while reducing the environmental effects. This study examines the physical and chemical properties of 60/70 penetration-grade asphalt binder, modified using POBA and warm mix asphalt (WMA) additive. Ranges of modified binder were prepared by adding 2% of the warm additive Rediset with different POBA contents (3%, 5%, 7% and 9%) throughout the wet mixing process. Physical properties of modified binder were obtained from penetration, softening point, ductility and rotational viscosity tests. Molecular components and structures of the modified binder were identified using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to determine the thermal properties of modified asphalt binder. The addition of 7% POBA in WMA binder showed the best characteristics in the tested consistency of its physical properties. As a modifier, POBA showed no chemical interaction with the molecules and structures of the asphalt binder and did not significantly change the physicochemical transitions. From the results, it can be concluded that using POBA in WMA binder for pavement construction is a viable option.

The study on potential use of RAP in WMA pavement layers with the inclusion of Basalt Fibers for the effect of mechanical and moisture Performance

Pavement engineers are facing difficulties for optimizing the use of natural resources and minimizing the consumption fuel involved in the manufacturing process of Hot Mix Asphalt (HMA). As a matter of fact the preparation of HMA involves in the release of harmful gases and to prevent, researches are working towards improving the environmental effects. Warm mix asphalt (WMA) is one of the solutions to increase the pavement performance with a concern to environmental effects that has gained a lot of popularity. In the present study, laboratory investigations were carried for the evaluation of laboratory prepared WMA mixes containing Reclaimed Asphalt Pavements (RAP) and with the inclusion of fiber at different proportion. This method of mix modification will not only lower the energy consumption but also reduce the release of harmful gases as observed in HMA mix proportions. Nevertheless the above mix combinations are intended to achieve sustainable pavement construction practices. The purpose of this research is to look into the effect of using RAP in modified mixes on mechanical and durability proportions in order to evaluate the effect of partial replacement of BC grade-2 WMA mixtures.. In this work, the effectiveness of basalt fibre modified bitumen mixtures was also examined using fibre in various amounts. Compaction test on binder modification, moisture damage, indirect tensile strength tests, and Marshall test effects on RAP, WMA mixes were used to assess the performance of binder modification, RAP, and fibre modified mixes. The laboratory test results indicated that the asphaltene proportions were shown better results at 3%WMA binder prepared with sasobit, a wax compound. The WMA asphalt mix prepared with RAP at 20% and with 0.6% of basalt fiber has provided better performance compared with the WMA mixes alone. This will certainly minimize the environmental effects through energy reduction and improved mechanical properties along with the durability performance.

Physical properties of palm oil boiler ash modified bitumen with Rediset

This study examines the physical properties of a 60/70 penetration grade bitumen modified using warm mix asphalt (WMA) additive, Rediset and palm oil boiler ash (POBA) as a modifier. Modified binders were prepared by adding 2% of Rediset with different POBA contents (3, 5, 7, and 9%) through wet mixing process. Physical properties of modified bituminous binder were obtained from penetration, softening point, rotational viscosity and ductility tests. The addition of 7% POBA in WMA binder has the best characteristics in term of its physical properties. The penetration values, softening point temperatures and ductility characteristics show inconsistent patterns. However, the rotational viscosity of each combination had decreased with the increment of temperature even though the trend was not significantly constant. Penetration index (PI) showed an increment with 3 and 5% and decrement pattern on 7 and 9% as well as penetration viscosity number (PVN) showing an inconsistent decrement with the addition of POBA. From the results, it can be concluded that using POBA in WMA binder for pavement construction is a viable option and can be further investigated.

Rheological and Chemical Evolution of HMA and WMA Binders Based on Ageing Kinetics.

It is fundamental to predict or estimate the rheological behavioural evolutions of binders and mixture to ensure a durability service life of the whole infrastructure. This study compared the long-term ageing kinetics of hot mix asphalt (HMA) and warm mix asphalt (WMA) produced with the same base bitumen. The difference in the component was that the WMA contained 1% of Cecabase warm agent and 5.5% of water by the weight of bitumen, to obtain a large expansion ratio (47 times). Rolling thin-film oven test (RTFOT) and pressure ageing vessel (PAV) laboratory ageing were carried out on the binder with or without the warm agent. The oven ageing procedure was conducted on the loose HMA and WMA mixtures for 0, 3, 6, and 9 days. Research results indicated that the dual effect of the studied warm agent and the foaming water sharply decreased the viscosity of the binder at a high temperature. Compared with the HMA, the warm agent improved the ageing resistance of the asphalt binder. However, higher content, such as 5.5 wt.%, of foaming water deteriorated viscosity due to a thinner bitumen film, which was more susceptible to oxidation. Therefore, less than 2 wt.% of warm agent and foaming water was recommended in the foamed WMA preparation.

Microwave Induction Heating of Polymer-Modified Asphalt Materials for Self-Healing and Deicing

This study evaluates the influence of polymer-modification on the induction heating capability of asphalt mastic in a microwave field, and investigates how effectively this approach can be utilized for ice melting and self-healing purposes. To this end, different asphalt mastic mixtures with different polymer-modification and mixing procedures were tested under microwave field exposure for induction heating capability, ice-melting ability, and self-healing capacity. The mixtures were made through warm-mix and hot-mix procedures with four bituminous binders, including virgin (unmodified) asphalt and the same binder modified with three types of polymers. The results showed the effectiveness of microwave induction heating of asphalt mastic for both crack-healing and deicing purposes. The binder type was found to influence the ice melting and crack healing rates, such that using a warm-mix asphalt binder resulted in a more efficient heat generation and conduction than using a virgin asphalt binder. While polymer-modification undermined induction-heating, ice-melting, and self-healing performances, SBS-modified asphalt binders exhibited better performance than the other polymer-modified binders.

Characterization of Fatigue Resistance of Warm Mix Binders Using Linear Amplitude Sweep Test

Fatigue failure in asphalt pavements occur due to the accumulation of damage under repeated traffic loading. Fatigue cracks generally occur within the binder phase of the asphalt mixture. Hence the specifications for properties related to fatigue resistance of asphalt binder become an important screening tool to select binders that are not inherently susceptible to fatigue under given environmental and traffic conditions. The Current Superpave Performance Grading (PG) specifications use parameter |G*|.·sinδ of asphalt binder to assess the fatigue susceptibility of asphalt mixes. These specifications do not accurately characterize the fatigue resistance of asphalt binders because |G*|.·sinδ is determined by applying a cyclic loading in the Dynamic Shear Rheometer (DSR) at a very small strain amplitude (1%). In this study, Linear Amplitude Sweep (LAS) test was considered to characterize the fatigue resistance of asphalt binders with warm mix additives. Warm mix asphalt (WMA) is a developing technology that can allow asphalt concrete to be produced at lower temperatures. This paper presents result of a study carried out to investigate the fatigue characteristics of warm-mix asphalt binders using a linear amplitude sweep test. Three warm-mix additives; Sasobit®, Evotherm™ and Rediset® are considered. Viscosity grade (VG 30), Polymer modified binder (PMB 40) and Crumb rubber modified binder (CRMB 60) were selected as base binders for this investigation. Physical and rheological tests were carried out for the characterization of these binders. The LAS test was carried out at 25 °C in a DSR, and the fatigue parameters were calculated from stress–strain plots. Test results showed that the changing trend in fatigue life of mixes is more related to the fatigue parameter Nf from LAS test than to |G*|. sinδ values of the binders. It was also observed that most of the warm mix binders have improved fatigue resistance at 25 °C in comparison to the control binders. The effect of Rediset® additive was found to be insignificant in the case of VG 30 grade binder only.

Evaluation of mix design volumetrics and cracking potential of foamed Warm Mix Asphalt (WMA) containing Reclaimed Asphalt Pavement (RAP)

ABSTRACT In this study, the mix design volumetrics and cracking potential of foamed Warm Mix Asphalt (WMA) containing various amounts of Reclaimed Asphalt Pavement (RAP) were evaluated. It was found that the increased coating ability of the foamed WMA binder counteracted the lowering of mixing and compaction temperatures for WMA. Therefore, both control HMA and foamed WMA exhibited similar mix design volumetrics up to certain lower temperatures. However, further reductions in the mixing and compaction temperatures for foamed WMA were found to exhibit improper mixing between aggregates and foamed binder. Despite foamed WMA exhibiting similar volumetric properties as HMA up to certain lower temperature, their fatigue cracking performance was found to be significantly different. The foamed WMA was found to exhibit higher cracking resistance compared to HMA in Louisiana Semi-Circular Bending (SCB) and Illinois Flexibility Index Test (I-FIT) tests. A similar trend in the cracking resistance was observed for coarser mixes in the Abrasion Loss Test (commonly known as Cantabro test). However, the Cantabro test could not screen finer mixes for their cracking resistance as it lacks a mechanistic basis. Finally, the foamed WMA technology was found to increase the cracking resistance of asphalt mixes. The higher RAP content in the foamed WMA, on the contrary was found to lower the cracking resistance of asphalt mixes due to incorporation of aged and stiffer binder from RAP.

Influence of Ultraviolet and Oxygen Coupling Aging on Rheological Properties and Functional Group Index of Warm Mix Asphalt Binder

Warm-mixed asphalt (WMA) has the characteristics of low mixing temperature and energy consumption, which makes it more suitable than hot-mixed asphalt for plateau regions (the altitude is above 500 m, and the terrain is relatively flat or has a wide area with certain undulations). However, WMA is subject to severe ultraviolet (UV) aging because the UV radiation in plateau areas is more intense. The asphalt’s aging changes its rheological properties inevitably, and thus degrades the asphalt pavement’s performance. Accordingly, the purpose of this paper is to investigate the effect of UV and oxygen coupling aging on WMA’s rheological properties and functional group index. Temperature and frequency sweep tests were performed with a dynamic shear rheometer. At the same time, the functional group index was used as an indicator to compare the changes in the WMA’s infrared spectrum before and after UV aging. The results showed that WMA’s elasticity increased and its viscosity decreased after aging with UV. Under the condition of UV–oxygen isolation, as the aging period increased, the WMA’s rutting factor increased gradually. The degree of improvement was greater than that under the condition of oxygen isolation. In contrast, the time required for the WMA’s complex shear modulus to recover under the condition of UV–oxygen coupling was delayed. An increase in the peak value of infrared spectrum indicates that the WMA has undergone oxygen aging. The presence and change in the carbonyl group reflects the degree of the WMA’s UV aging, and the UV aging condition had a greater effect on the peak values of the carbonyl and sulfoxide groups.

Environmental impact evaluation and long-term rutting resistance performance of warm mix asphalt technologies

The adoption of warm mix asphalt (WMA) technologies is well accepted due to its promising environmental benefits, however, their long-term field performance is not well understood. This study focused on the long-term rutting resistance of WMA and their companion hot mix asphalt (HMA) based on 83 field samples collected from 28 field projects across the United States covering four climate zones, and quantified environmental impacts for various WMA technologies as compared to HMA. Field cores were evaluated by dynamic modulus, creep compliance, and Hamburg wheel-tracking device tests. Asphalt binders extracted from field cores were evaluated by continuous performance grading (PG), multiple stress creep recovery (MSCR), and monotonic shear tests. The results showed that WMA binders exhibited similar rutting resistance compared with the HMA binders after long-term field aging. Existence of polymer in the asphalt binder was displayed through the plot of non-recoverable creep compliance and percent recovery. The long-term field aged polymer modified asphalt binders for WMA and HMA were comparable. The results also showed that the CO2 reduction by using WMA ranged from 89.09% to 42.79% depending on WMA type. On average, the CO2 emission was reduced to 66.89% by using WMA technologies. Overall, environmental impact analysis and long-term field performance results validated the confident use of WMA technologies.

Effect of laboratory long-term oven aging on the stiffness of asphalt mixtures

This study evaluates the effect of laboratory long-term oven aging (LTOA) on the stiffness of asphalt mixture using laboratory dynamic modulus test. A large variety of materials was subjected to diverse LTOA conditions including different aging temperatures and durations with loose mixture and compacted samples. Dynamic modulus master curve and dynamic modulus ratio (DMR) data shows that the aging of loose mixture at 95 °C could be an ideal LTOA procedure with the efficiency and capability to characterize the long-term aging in the field. The variety of materials including the use of recycled asphalt pavement, warm mix asphalt technologies and asphalt binder performance grade was also found to have appreciable effect on the LTOA properties.

High-Temperature Performance and Workability of Crumb Rubber–Modified Warm-Mix Asphalt

Abstract Crumb rubber produced from scrap tires has been widely applied in asphalt mixtures to improve the pavement performance. Warm-mix technology has also been employed to lower the production temperature of asphalt mixtures. The objective of this article is to investigate the effects of warm-mix additive types and crumb rubber concentration on the resistance to deformation of crumb rubber–modified (CRM) binders through the repeated creep and recovery test (RCRT), dynamic shear rheometer (DSR), and rotational viscosity test. The CRM binders with crumb rubber concentrations of 10 %, 15 %, 20 %, and 25 % were prepared first as the control binders. Then, three types of warm-mix additives, Sasobit, RH, and Advera, were added into the CRM asphalt to produce CRM warm-mix asphalt (WMA) binder. Generally, the workability of CRM asphalt can be improved with the addition of warm-mix additives. The effect of warm-mix additive on the high-temperature performance is highly dependent on the crumb rubber dosage. The RCRT results overall showed that the warm-mix additives can improve the high-temperature performance of asphalt when the crumb rubber concentration is low. However, according to the DSR test, Sasobit improved the rutting resistance of CRM asphalt, while the RH and Advera sacrificed the rutting resistance. The inconsistency between the RCRT and DSR results suggests that it may be necessary to conduct both the tests when investigating the high-temperature performance of CRM asphalt with warm-mix additives.