Search

This study evaluates the laboratory performance of Warm-Mix Asphalt (WMA) containing locally sourced Steel Slag (SS) and limestone (LS), focusing on stiffness and moisture sensitivity. Four asphalt mixes were tested: Hot mix with limestone (HL), hot mix with steel slag (HS), warm mix with limestone (WL), and warm mix with steel slag (WS). The binder used for all mixes was AC 60/70 penetration grade, and Aspha-min served as the warm mix additive. Testing included Marshall Stability, boiling water, indirect tensile strength, moisture-induced damage (TSR), and dynamic modulus. Image Analysis quantified the aggregate-retained coated area after the boiling test. Despite performance differences, all mixes met Egyptian code requirements for asphalt concrete mixes. Visual inspection and image analysis demonstrated the effectiveness of using steel slag to mitigate asphalt mix stripping. The retained coated area for limestone mixes ranged from 60 % to 75 %, while SS mixes exhibited over 95 %. Dynamic modulus tests indicated no significant stiffness difference with SS, and stability increased by 8 % and 14 % with and without the warm additive. Economic study confirmed the feasibility of utilizing SS. In conclusion, combining Aspha-Min and steel slag improves AC mix production and construction processes, offering a sustainable and advantageous option in Egypt. [ABSTRACT FROM AUTHOR]

This study evaluates the laboratory performance of Warm-Mix Asphalt (WMA) containing locally sourced Steel Slag (SS) and limestone (LS), focusing on stiffness and moisture sensitivity. Four asphalt mixes were tested: Hot mix with limestone (HL), hot mix with steel slag (HS), warm mix with limestone (WL), and warm mix with steel slag (WS). The binder used for all mixes was AC 60/70 penetration grade, and Aspha-min served as the warm mix additive.Testing included Marshall Stability, boiling water, indirect tensile strength, moisture-induced damage (TSR), and dynamic modulus. Image Analysis quantified the aggregate-retained coated area after the boiling test. Despite performance differences, all mixes met Egyptian code requirements for asphalt concrete mixes.Visual inspection and image analysis demonstrated the effectiveness of using steel slag to mitigate asphalt mix stripping. The retained coated area for limestone mixes ranged from 60 % to 75 %, while SS mixes exhibited over 95 %. Dynamic modulus tests indicated no significant stiffness difference with SS, and stability increased by 8 % and 14 % with and without the warm additive. Economic study confirmed the feasibility of utilizing SS. In conclusion, combining Aspha-Min and steel slag improves AC mix production and construction processes, offering a sustainable and advantageous option in Egypt.

With the increasing consideration of sustainability in infrastructure materials, both modified asphalt and warm-mix asphalt have received remarkable attention. However, little is known about characteristics of warm-mix styrene-butadiene-styrene (SBS) modified asphalt with foaming technique (FWMA-SBS). The present study is dedicated to optimizing fabrication of the FWMA-SBS binder and investigating the performance of the foamed SBS-modified asphalt mixture. To achieve desirable foaming characteristics, the FWMA-SBS binder is produced at foaming temperature of 130°C, water content of 2.0%, and air pressure of 0.55 MPa. The production temperature of the FWMA-SBS mixture is significantly lowered by 20°C compared to traditional SBS-modified asphalt mixture. It has demonstrated that engineering performance of FWMA-SBS binder coincides with the mixture. The FWMA-SBS mixture features better low-temperature cracking resistance and fatigue performance, while it exhibits lower rutting resistance and similar moisture stability in comparison with a traditional SBS-modified asphalt mixture. The sustainability assessment verifies that compared to conventional SBS-modified asphalt mixture, the production of 1 ton of FWMA-SBS mixture leads to energy savings of 9.8%, cost reduction of $1.81, and less energy associated with CO2 by 9.8%. The research accomplishments promote the utilization of the foamed SBS-modified asphalt, realizing the pavement sustainability from principles to practices. [ABSTRACT FROM AUTHOR]

A study was undertaken to evaluate the influence of an organic and a chemical additive on the short- and long-term ageing properties of warm-mix asphalt containing reclaimed asphalt pavement. Various mechanical tests, including dynamic creep, indirect tensile strength, semi-circular bending and resilient modulus, were conducted. The results indicated that the mixture containing reclaimed asphalt pavement without additives showed a higher flow number in both non-ageing and ageing processes, indicating higher resistance to rutting. The mixture containing the chemical additive demonstrated higher resistance to moisture susceptibility in comparison to the one with the organic admixture. Moreover, the mixtures containing recycled asphalt pavement and the chemical additive showed higher fracture energy than mixtures containing recycled asphalt pavement and the organic additive, while the latter showed the highest resilient modulus in the non-ageing and ageing process. [ABSTRACT FROM AUTHOR]

The application of warm-mixing technology brings considerable economical and environment benefits by decreasing the mixing temperature during warm asphalt mixture (WMA) production. However, the possible water residue also generates concerns for moisture susceptibility. For deep investigation on the influencing factors and mechanisms of the moisture susceptibility of WMA, surface free energy (SFE) tests and laboratory tests are applied in this research. A novel indicator based on SFE, namely, effective adhesion work, is proposed to assess the asphalt–aggregate adhesion with different moisture contents. Then, given the mixing procedure of the dry-mixing method, an advanced three-phase model as a form of asphalt–aggregate-warm mixing additive is introduced, improving the conventional two-phase asphalt–aggregate model for better reflecting the separate addition of warm-mixing additives during mixing. Afterwards, the influence of aggregate type, asphalt type, aggregate moisture content, warm-mixing agent type, and the warm-mixing process on the moisture susceptibility of WMA is analyzed utilizing the models and indicators proposed. Finally, the validity of the SFE indicator is verified by comparing the calculation of effective adhesion work with freeze–thaw splitting test results. The results show that all of the above factors impact the moisture susceptibility of WMA by influencing the interfacial adhesion, with the effect of moisture content being the most significant. Meanwhile, effective adhesion work and the three-phase model brought out in this research are proven to be feasible to characterize the adhesion properties of WMA, offering theoretical support to the research on warm-mixing technology. [ABSTRACT FROM AUTHOR]

To optimize the rheological properties of warm-mix asphalt and analyze its ultraviolet (UV) aging behaviors, organic montmorillonite was selected to modify the Sasobit warm-mix asphalt. 3% Sasobit was added into the hot mix asphalt to prepare warm-mix asphalt; and then, three different contents of organic montmorillonite (1%, 2%, and 3%) were added to modify the warm-mix asphalt compositely. Subsequently, the road performance and UV aging behaviors of prepared asphalt were evaluated by some rheological indicators; and then, the modification mechanism was investigated by micro testing methods, including Fourier transform infrared spectroscopy (FTIR) test and Fluorescent microscope (FM) test. Results show that with the introduction of Sasobit, construction workability and high-temperature properties of hot mix asphalt were improved, while its fatigue performance and low-temperature properties were decreased. Fortunately, adding organic montmorillonite into the prepared warm-mix asphalt can significantly optimize its fatigue performance while having little influence on its low-temperature properties. UV aging test results show that DSRFn is the most sensitive indicator to characterize the UV aging behaviors of asphalt. Meanwhile, DSRFn aging indexes of warm-mix asphalt and those with 1%–3% organic montmorillonite were reduced by 28.88%, 46.41%, 48.55%, and 46.15%, respectively, compared with that of hot mix asphalt, indicating that Sasobit warm-mix asphalt has superior aging resistance than hot mix asphalt and that the addition of organic montmorillonite can further improve this ability. Microscope test results confirm that the intercalated structure or exfoliated structure may be formed in the asphalt binders, thereby enhancing the rheological properties. In accordance with the presented results, it is recommended that the optimum content of montmorillonite is 2%, which can promote the prepared asphalt samples to obtain excellent rheological properties. [ABSTRACT FROM AUTHOR]

Roads account for a major part of energy/resource consumption and emission of GHGs, such as CO2, PM, NOx, O3, etc., due to high demand for virgin materials, specifically in developing regions. The applicability of recycled materials, such as recycled asphalt pavement (RAP) and other alternative approaches for, e.g., warm-mix asphalt (WMA), in developed countries is hindered by project-specific constraints and lack of empirical studies in these regions. Lifecycle assessment studies on the usage of these road options from actual projects in the developing countries can aid decision makers choose sustainable material approaches by providing case study examples as guidelines. To that end, this study analyses environmental in/out-flows for a traditional approach and multiple green approaches (RAP and WMA) for a major highway section in Abu Dhabi through a 30-year (2015–2045) lifecycle approach. Roadworks were modelled in SimaPro according to real-world conditions, and the expected burden mitigation in each stage is calculated. Benefits of using optimum RAP-based options and a virgin-material-based WMA case against the baseline virgin material case were also investigated. Results showed benefits of WMA as higher than replacing virgin asphalt with recycled asphalt (25% RAP asphalt base, 15% RAP binder and wearing courses). Land use (19%) and energy consumption (16%) showed the highest reduction, followed by ozone depletion (14%), ionizing radiation (11%), PM (8%), acidification (7%) and global warming potential (6%) across all pavement lifecycle stages and environmental indicators. Similar results were obtained for other scenarios with lesser degrees of reduction, which show the significance of replacing HMA with WMA for real-world projects, specifically in mega road projects in Abu Dhabi and the Middle East towards cutting the significant carbon footprint of asphalt pavements.

Moisture and stripping damages are the most prevalent cause of defects of both Hot-Mix Asphalt (HMA) and Warm-Mix Asphalt (WMA). Adhesion between aggregates and bitumen is a crucial factor that affects such defects. Various methods, such as incorporating additives, have strengthened the asphalt mixture's resistance to moisture and stripping. This paper aimed to experimentally investigate the effect of including a low-cost polymer additive (Superplast) into HMA and WMA mixtures. For this goal, a 60/70 penetration grade bitumen was used. For preparing the WMA mixtures, Showax was employed with percentages of 2, 3, 4, 5, and 6% by weight of bitumen. Polymer modified mixtures (HMA and WMA) were prepared by adding 3%, 4, and 5% of Superplast by weight of the binder. Performance characterizations of the unmodified and Superplast-modified mixtures include stiffness, moisture damage resistance, and bonding. These characteristics were evaluated via Marshall, Lottman, and Double Punching tests, respectively. Results revealed that incorporating Superplast improved the adhesion between bitumen and aggregates, which ultimately led to an increase in the stiffness and moisture resistance of both HMA and WMA. Moreover, Superplast-modified WMA mixtures exhibited the best moisture and stripping resistance performance compared to Superplast-modified HMA and other unmodified mixtures.

The application of warm-mixing technology brings considerable economical and environment benefits by decreasing the mixing temperature during warm asphalt mixture (WMA) production. However, the possible water residue also generates concerns for moisture susceptibility. For deep investigation on the influencing factors and mechanisms of the moisture susceptibility of WMA, surface free energy (SFE) tests and laboratory tests are applied in this research. A novel indicator based on SFE, namely, effective adhesion work, is proposed to assess the asphalt–aggregate adhesion with different moisture contents. Then, given the mixing procedure of the dry-mixing method, an advanced three-phase model as a form of asphalt–aggregate-warm mixing additive is introduced, improving the conventional two-phase asphalt–aggregate model for better reflecting the separate addition of warm-mixing additives during mixing. Afterwards, the influence of aggregate type, asphalt type, aggregate moisture content, warm-mixing agent type, and the warm-mixing process on the moisture susceptibility of WMA is analyzed utilizing the models and indicators proposed. Finally, the validity of the SFE indicator is verified by comparing the calculation of effective adhesion work with freeze–thaw splitting test results. The results show that all of the above factors impact the moisture susceptibility of WMA by influencing the interfacial adhesion, with the effect of moisture content being the most significant. Meanwhile, effective adhesion work and the three-phase model brought out in this research are proven to be feasible to characterize the adhesion properties of WMA, offering theoretical support to the research on warm-mixing technology.

Roads account for a major part of energy/resource consumption and emission of GHGs, such as CO2, PM, NOx, O3, etc., due to high demand for virgin materials, specifically in developing regions. The applicability of recycled materials, such as recycled asphalt pavement (RAP) and other alternative approaches for, e.g., warm-mix asphalt (WMA), in developed countries is hindered by project-specific constraints and lack of empirical studies in these regions. Lifecycle assessment studies on the usage of these road options from actual projects in the developing countries can aid decision makers choose sustainable material approaches by providing case study examples as guidelines. To that end, this study analyses environmental in/out-flows for a traditional approach and multiple green approaches (RAP and WMA) for a major highway section in Abu Dhabi through a 30-year (2015–2045) lifecycle approach. Roadworks were modelled in SimaPro according to real-world conditions, and the expected burden mitigation in each stage is calculated. Benefits of using optimum RAP-based options and a virgin-material-based WMA case against the baseline virgin material case were also investigated. Results showed benefits of WMA as higher than replacing virgin asphalt with recycled asphalt (25% RAP asphalt base, 15% RAP binder and wearing courses). Land use (19%) and energy consumption (16%) showed the highest reduction, followed by ozone depletion (14%), ionizing radiation (11%), PM (8%), acidification (7%) and global warming potential (6%) across all pavement lifecycle stages and environmental indicators. Similar results were obtained for other scenarios with lesser degrees of reduction, which show the significance of replacing HMA with WMA for real-world projects, specifically in mega road projects in Abu Dhabi and the Middle East towards cutting the significant carbon footprint of asphalt pavements. [ABSTRACT FROM AUTHOR]

Moisture and stripping damages are the most prevalent cause of defects of both Hot-Mix Asphalt (HMA) and Warm-Mix Asphalt (WMA). Adhesion between aggregates and bitumen is a crucial factor that affects such defects. Various methods, such as incorporating additives, have strengthened the asphalt mixture's resistance to moisture and stripping. This paper aimed to experimentally investigate the effect of including a low-cost polymer additive (Superplast) into HMA and WMA mixtures. For this goal, a 60/70 penetration grade bitumen was used. For preparing the WMA mixtures, Showax was employed with percentages of 2, 3, 4, 5, and 6% by weight of bitumen. Polymer modified mixtures (HMA and WMA) were prepared by adding 3%, 4, and 5% of Superplast by weight of the binder. Performance characterizations of the unmodified and Superplast-modified mixtures include stiffness, moisture damage resistance, and bonding. These characteristics were evaluated via Marshall, Lottman, and Double Punching tests, respectively. Results revealed that incorporating Superplast improved the adhesion between bitumen and aggregates, which ultimately led to an increase in the stiffness and moisture resistance of both HMA and WMA. Moreover, Superplast-modified WMA mixtures exhibited the best moisture and stripping resistance performance compared to Superplast-modified HMA and other unmodified mixtures. [ABSTRACT FROM AUTHOR]

The study compares warm-mix asphalt concrete (WMA) and a traditional hot mix asphalt concrete (HMA), evaluating permanent deformation, fatigue, stiffness modulus, and water sensitivity. The cost (construction only) differences are also addressed. Three WMA blends were prepared. One WMA was manufactured with the stand alone organic wax and incorporated 60% of recycled concrete aggregate (RCA). The other two used organic wax embedded in cellulosic fibres, one of them incorporated 35% of reclaimed asphalt pavement (RAP), and the other had no added sub-product. Trial sections were constructed with plant-produced mixtures, laid and compacted with conventional equipment. When considered a global indicator representing mixtures mechanical behaviour involving deformation, rutting, fatigue and moisture resistance, the results showed that performance of WMA blended with RAP and RCA was similar to HMA, and the conventional WMA was 25% better. The construction process proved to be feasible for any WMA. The direct construction costs as compared to conventional HMA were 6% higher for the conventional WMA and 5–8% lower when WMA used sub-products. The use of these sub-products is aimed to find innovative approaches to be undertaken throughout the product lifecycle, from manufacture through reuse, with the goal of reducing waste going to landfill. [ABSTRACT FROM AUTHOR]

The paper investigates the phenomena of adhesion in binder-aggregate systems produced to reflect warm-mix asphalt with water-foamed bitumen. The investigated materials included limestone and quartzite aggregates and a total of four asphalt binders: 50/70 and 45/80–55 bituminous binders obtained from two sources. The adhesive bonding between the asphalt binders and aggregates was evaluated in boiling water stripping tests, which results were quantified using digital image analysis. The bituminous binders were additionally tested for their dynamic viscosities, and their chemical composition was probed using FTIR spectroscopy. The tests were carried out using traditional liquid and foamed bituminous binders on samples prepared at temperatures characteristic of hot-mix asphalt and warm-mix asphalt production (20 °C decrease). The use of foamed binders yielded higher values of residual asphalt binder coverage of the aggregates. Limestone aggregates provided superior adhesion, with the lowest result amounting to approximately 88%, while with quartzite aggregates, the results ranged from approximately 40% to 87%. The refinery from which the asphalt binders were sourced had a significant influence on the results; however, the additional rheological and chemical analyses were insufficient to explain those differences. It was concluded that the process of asphalt binder foaming, per se, may have a beneficial impact on the resistance of the asphalt binder-aggregate system to the action of water.

Warm-mix asphalt (WMA) additives are widely used to reduce the mixing and compaction temperatures of the bituminous mixes. Due to lower aging temperature, one can expect a reduction in aging compounds in a WMA mix in comparison with the hot-mix asphalt (HMA) mix. In this study, an attempt is made to address the influence of the production process and the presence of WMA additive on the aging compounds formed in WMA binders. For this purpose, two binders, one unmodified (VG20 grade), and a crumb rubber modified, were used. A chemical WMA additive, Evotherm, was used. All the binders were subjected to short-term and long-term aging in the laboratory. The carbonyl and sulfoxide functionalities in all the binders were quantified using Fourier transform infrared spectroscopy. From the analysis, it was seen that the carbonyl index for WMA-modified VG20 binder and crumb rubber-modified binder (CRMB) are higher by 25 and 33% compared to the base VG20 binder and CRMB, respectively. Also, Evotherm-modified binders resulted in lower carbonyl compounds (about one-half) when compared with the HMA binders, aged at identical conditions. The magnitude and the rate of formation of sulfoxide compounds, however, varied with different binders owing to the overlapping effects of the formation and decomposition of sulfoxides. [ABSTRACT FROM AUTHOR]

Highlights • The densification through SGC reduces the compaction temperature of WMA. • Adding 1.5 and 3% of greasy diamide (additive) reduces the compaction temperature. • Additive reduces the phase angle and increase the dynamic shear rheological modulus. • Greasy diamide added up to 3% improved the viscosity and the lubricity of the WMA. • The rheological and mechanical properties of WMA reach the same level as HMA. Abstract Warm-mix asphalt (WMA) containing additives is used to decrease both the costs and harmful effects to the environment by reducing the viscosity, mixing temperature and compaction energy of asphalt without affecting its mechanical and dynamic properties. The lubricity effect is important in the densification of the mixture and must be measured during compaction (using a Superpave gyratory compactor). This work analyzes the impact of the addition of greasy diamide (DG) on the rheological-mechanical properties of dense-grade mixtures manufactured with asphalt AC-20 by examining a reference sample (HMA) and three improved samples (WMAs) with different percentages (1.5, 3.0 and 4.5%) of greasy diamide. The type of aggregate, content and type of asphalt and compaction energy were found to remain constant in the test mixtures. The rheological properties were measured according to current regulations, and the deformation was determined using a uniaxial cyclic compressive tester and a Hamburg loaded wheel. The results showed that the addition of greasy diamide to WMA improved the rheological properties while decreasing the compaction temperature and maintaining densification without significantly affecting the mechanical behavior. [ABSTRACT FROM AUTHOR]

Highlights • The chemical and rheological parameters were sensitive to material composition. • Fair to good correlations were observed among chemical and rheological properties. • All binder parameters yielded generally consistent observations with SCB J c. • The best ranking agreement with SCB J c was provided by Carbonyl Index and A LAS. Abstract This study was aimed to evaluate chemical and rheological properties of recovered asphalt binders, and to ascertain their implications on crack resistance as determined by the semi-circular bend test on the asphalt mixtures. The asphalt mixtures incorporated various contents of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) and warm-mix asphalt (WMA) technologies. The determined asphalt binder parameters generally presented consistent trends with respect to RAP/RAS content. The WMA technologies evaluated were found to produce mixtures with similar cracking performance with the conventional hot-mix asphalt mixtures. The rank correlations between asphalt properties and mixtures' crack resistance was also evaluated. [ABSTRACT FROM AUTHOR]

Highlights • Work of adhesion of may drop up to 50% when aggregate moisture content of 10%. • Bond energy of WMA mixes diminish less with increasing aggregate moisture contents. • PM binder bond energy showed about 6.7 times greater than that of AC20 binders. • Quadrant plot can effectively rank the asphalt-aggregate adhesion properties. Abstract Warm-mix asphalt (WMA) is one technology that has been found to have potential in minimizing the environmental harm caused by road construction activities. Its low mixing and compacting temperatures have opened great opportunities for more sustainable development. However, because WMA is mixed at low temperatures, the drying process of the aggregate may fail to dry the WMA completely. The binder-aggregate adhesion property can be damaged by moisture remaining from incomplete drying. The present study investigated the effects of aggregate moisture on the binder-aggregate interfacial characteristics of WMA by evaluating its surface free energy and adhesive bond strength. The results showed that for the Pen 60-70 binder type, the aggregate AG in general showed the higher bond energy and aggregate SD showed the lowest bond energy among three aggregate types. Also, the bond energy diminishes with increasing aggregate moisture contents but the percent drops in bond energy is less when WMA additives was included. For the PM binder, SL aggregate group showed the highest bond energy and SD aggregate group showed the lowest bond energy. For the work of adhesion, the results showed that with aggregate with 10% moisture contents has destructive effects on the work of adhesion which may decrease to 50% compare to dry aggregate condition. Finally, the four quadrant diagrams can be used to combine two distinct property of the bond energy and the work of adhesion as the hybrid performance indicator to rank the effect of moist aggregate to the adhesion properties at binder-aggregate interface. [ABSTRACT FROM AUTHOR]

This paper presents results stemming from a comparative experimental analysis of two warm-mix asphalts (WMA) and a dense-graded hot-mix asphalt (HMA). In order to evaluate asphalt mixture behavior, physical and rheological tests were conducted, including tests on resilient modulus, resistance to moisture-induced damage, resistance to fatigue and resistance to permanent deformation. Samples studied were subjected to short (STOA) and long-term (LTOA) aging. As far as asphalt mixture composition is concerned, the same particle size distribution and coarse aggregate were employed for both mixture types. The control HMA mixture was produced with AC 60-70, and the WMAs used the same asphalt cement modified with two chemical additives (Rediset WMX® and Cecabase RT®). The modified mixtures exhibited better resistance to permanent deformation, aging and moisture-induced damage (versus the control mixture). Likewise, WMAs generally saw increased fatigue resistance under controlled-stress loading, which rheological characterization showed is mainly attributable to binder additives and their concomitant modifications.

This paper focuses on the comparison of the mechanical performance of three warm-mix asphalt (WMA) blends with recycled concrete aggregate (RCA) or electric arc furnace slag (EAFS) as substitutes of part of the aggregate. A conventional hot mix asphalt (HMA) and a WMA without by-products were used as references. The evaluation was carried out in a laboratory by means of testing specimens taken from experimental pavement sections built in real production, laying and compaction circumstances. Performance testing included wheel-tracking tests, four-point bending tests, and indirect tensile strength to assess water sensitivity. An organic wax and a chemical surfactant were applied to lower handling temperatures of the WMA under study. Apart from the HMA and the WMA used as references, the study evaluated the influence of introducing 60% of RCA or 30% of EAFS into the WMA blends as substitutes of the aggregate. The obtained results for the WMA with by-products tested allowed to conclude that the introduction of EAFS or RCA into the WMA blends increases Marshall stability and may increase or decrease resistance to rutting. Findings also showed that stiffness modulus is somewhat reduced and fatigue resistance does not change significantly. Additionally, water sensitivity is slightly reduced. Comparing these results with the performance observed elsewhere for WMA without by-products revealed that the addition of RCA or EAFS is satisfactory. The construction of experimental sections used conventional batch plant, paver and compactors without any noticeable technical problems. [ABSTRACT FROM AUTHOR]

This paper presents a feasibility of a modified Asphalt Bond Strength (ABS) test method for use with a new adhesion testing device with three different pullout stubs and its application for evaluating Polyethylene (PE) wax-based Warm Mix Asphalt (WMA) additive. Four different asphalt binders were used to evaluate the feasibility of applying the existing AASHTO ABS test method using a new ASTM-certified adhesion testing device and three different pullout stubs. The modified ABS test method was used to evaluate the loss of adhesion and cohesion in asphalt bond strength due to moisture-induced damage. The paper also discusses rheological properties of extracted asphalt binders from three different test sections in Minnesota, Ohio and Iowa constructed using PE wax-based WMA additive and different amounts of Reclaimed Asphalt Pavement (RAP) materials. Based on the modified ABS test results using the new adhesion testing device, it was found that the proposed pullout stub with 0.0 mm thickness (no edge) exhibited consistent results. Based on the results from extracted asphalt performance grading and the multiple stress creep recovery (MSCR) test, it was found that the PE wax-based WMA additive, which was specially designed for asphalt mixtures with a high RAP content, significantly improved the rheological properties of aged asphalt binders from RAP materials. [ABSTRACT FROM AUTHOR]

This study proposes an aggregate pre-coating approach using both a synthesized thermoset polymer and an asphalt emulsion as a warm-mix asphalt mixture. An oil-in-water emulsified asphalt is added to initiate a moisture hardening reaction for aggregate coating with the polymer on the surface of the aggregate. Then, the PG64-22 asphalt binder is finally mixed with the pre-coated aggregates in the temperature range of 120–130 °C. The chemically modified epoxy can react with some polar components on the surface of aggregates, and it bonds with nonpolar groups in an asphalt binder so that it gives high adhesive strength on the surface of aggregates. The surface strength of the synthesized epoxy was at least 2-fold greater than the general epoxy sample, as verified by the Dolly test. The chemically modified epoxy was used as a coating agent for aggregates and made possible to react with the water molecules in the emulsified asphalt binder. The bonding effect was verified by the boiling test, maintaining greater than 90% of the coated film. [ABSTRACT FROM AUTHOR]

As tunnels are now longer and built more frequently, fire safety in tunnels has become a major issue throughout the world. The objective of this study is to investigate the flame resistance of warm-mix asphalt mixtures with flame retardants through a comprehensive testing program. In this study, a compound flame retardant (FR) was added to the asphalt and warm-mix asphalt. The comprehensive testing program included the flash point test and oxygen index test of the asphalt binder, the combustion test of loose and compacted mixtures, and a bench scale apparatus for combustion testing of asphalt mixtures in order to understand the flame resistance of the asphalt and mixtures. The results of the asphalt binder tests indicate that FR has no significant effect on the flash point but has an obvious effect on the fire point, and FR asphalt requires more oxygen because the FR prevents it from burning. During various combustion tests, the FR reduced the flame, lessened the smoke, and lowered the temperature but noticeably increased the burning time. It was noticed that the structural integrity of the burned FR mixture samples is preferable to the mixture without FR. The bench scale apparatus for combustion testing shows that the ignition time is extended, both the heat release and smoke for the FR mixtures are noticeably decreased, and both the carbon monoxide (CO) and carbon dioxide (CO2) emissions are reduced. This means FR mixtures have better flame resistance and will have less potential for environmental pollution. Moreover, the results also show that a warm-mix asphalt additive has little effect on the flash point, fire point, or oxygen index of the asphalt. It also has little effect on the burning time and the flame height of loose mixtures. Because the warm-mix asphalt additive aids combustion, it decreases the maximum temperature and mass loss of the compacted mixtures during the firing process. It also shortens the ignition time and decreases the released heat, the total smoke, and the release of CO and CO2. Thus, the flame resistance of warm-mix asphalt with FR is the best due to the combined effect of the FR and the warm-mix asphalt additive, which means that the combination of modified asphalt is preferable for asphalt pavement in tunnels. [ABSTRACT FROM AUTHOR]

A 50/70 bitumen was modified with five different commercial waxes, including Fischer-Tropsch, Montan and functionalized waxes. Thermal and morphological properties were investigated through Differential Scanning Calorimetry (DSC) and polarized optical microscopy (POM). Dynamic and continuous rheological tests were carried out to analyse the mechanical response of wax-modified bitumens (WMB). Theories behind possible mechanisms of asphalt/wax interaction are discussed. The entire frequency/temperature domain was divided into two macro-regions. The first one covers the glassy state, with independent waxy structures, where the bitumen mainly determines the mechanical response. The second macro region develops along the intermediate viscoelastic domain and propagates towards high temperatures/low frequencies. Within this domain, all WMB exhibits a complex mechanical response, with gel-like characteristics, thus suggesting the existence of physical networks and interconnections between contiguous wax crystalline segments. [ABSTRACT FROM AUTHOR]

Temperature segregation, which occurs as a result of differential cooling of asphalt mixtures, is a serious challenge during asphalt paving operations. The objective of this study is to investigate temperature segregation caused by paver stoppage through field measurements, laboratory tests, and finite-element (FE) analyses. Five Louisiana asphalt rehabilitation projects were selected for the study. A multisensor infrared temperature scanning bar (IR-bar) system was used for field measurements of the real-time thermal profiles of uncompacted asphalt mats behind the paver. Laboratory performance of thermally segregated asphalt pavements from three selected projects were evaluated by measuring the fracture resistance of field asphalt samples at 25°C using the semicircular bend (SCB) test. From field measurements, it was clear that temperature segregation occurs whenever the paver stops, and the level of segregation (temperature drop) is dependent on the duration of paver stoppage, e.g., temperature segregation of more than 55°C can occur within less than 1 h of the stoppage. Laboratory performance test results showed that the asphalt samples from unsegregated areas generally had better fracture resistance than the samples from the segregated areas did. FE analysis results showed nonlinear decreases of temperature in the uncompacted asphalt mats. Furthermore, the cooling rate of hot-mix asphalt (HMA) was almost twice as fast as the warm-mix. To avoid high-severity temperature segregation (more than 21°C), it is recommended that paver stoppage time should be kept minimum with a maximum duration of 4 min for hot-mix and 6 min for warm-mix asphalts, respectively. [ABSTRACT FROM AUTHOR]

This paper compares several warm-mix asphalt (WMA) blends and hot mix asphalt (HMA) in terms of their resistance to permanent deformation (wheel-tracking tests), fatigue performance and stiffness modulus (four-point bending tests), and water sensitivity (indirect tensile strength ratio). The first stage of the study included the production of Marshall specimens in laboratory to evaluate stability and flow of the blends’ specimens as well as their volumetric properties, aiming to select the most promising to apply in the field. WMA technologies involved the addition of four different products: a chemical surfactant, an organic wax, a chemical surfactant combined with cellulosic fibres and organic wax embedded in cellulosic fibres. One WMA blend incorporated 35% of reclaimed asphalt pavement (RAP). The second stage of the project involved the construction of trial sections in the field with plant-produced mixtures, laid and compacted with conventional equipment. Laboratory performance testing was carried out on specimens collected from the trial sections. The results showed that the level of mechanical performance of WMA was, globally, satisfactory and similar to the obtained for the HMA used as reference. Nevertheless, the warm-mix with surfactant additive revealed high sensitivity to temperature. The blend with RAP suffered some influence from the variation of binder quantity added by the RAP. The construction process in real production conditions proved to be feasible. [ABSTRACT FROM AUTHOR]

Characteristics of dynamic modulus (| E ∗ |) and phase angle ( δ ) functions of hot-mix asphalt (HMA) are well known from years of laboratory tests and available models in the literature. On the other hand, the | E ∗ | and δ functions of warm-mix asphalt (WMA) are not well defined yet for reasons like relatively newer use in United States as well as manufactured by using various WMA technologies (e.g. foaming, Evotherm, Cecabase RT, etc.) which use different WMA agents. This study evaluates the effects of different WMA agents on the | E ∗ | and δ of asphalt concrete (AC). A control HMA and four WMA mixtures were collected from a plant with identical aggregate type and size distribution. The loose AC mixtures were then compacted, cored and sawed to cylindrical specimens for | E ∗ | and δ testing in the laboratory. Statistical evidence showed that WMA agents significantly affect the | E ∗ | and δ of AC mixture. The | E ∗ |-values of HMA and WMA are comparable at mid-range frequencies only, indicating that fatigue performances at operational temperature of WMA and its HMA counterpart may be similar. However, high temperature rutting and low temperature cracking may not be similar for WMA and its HMA counterpart. [ABSTRACT FROM AUTHOR]

In recent years, numerous studies have been carried out on new technologies allowing to reduce of mix asphalt production temperatures. One of the possibilities is to foam the asphalt with “water-containing” additives, which include zeolites. So far, mainly synthetic zeolites of the Linde A structure type, obtained from chemical reagents, and natural clinoptilolite have been used in WMA technology. In this studies, the synthetic zeolites produced from fly ashes with 4 different types of crystalline structure were analyzed. Zeolite materials were characterized by textural parameters and thermal analysis. The amount of zeolite added to asphalt was 0, 3, 5, 7 wt % in relation to the weight of asphalt. Determination of dynamic viscosity was performed at two temperatures: 135 and 160 and 4 time intervals. The tests were performed for two asphalt binders: 35/50 and 100/150 penetration grade. As a conclusion, it was found that the viscosity of asphalt pastes with zeolitic materials increases with the increase in the amount of zeolite added. The increase level depends mainly on the textural parameters. The potential usefulness of fly ash derived zeolites in the process of asphalt foaming, which depends mainly on the amount of water contained in the zeolite structure and the method of its release, has been proved.

• The application of various environment-friendly materials in SFP was realized. • SFP with significant energy-saving and emission-reduction benefits was designed. • The environmental benefits of SFP in the whole life cycle were analyzed. Semi-flexible pavement (SFP) has excellent potential to improve pavement performance and durability. This study aims to reduce energy consumption and emissions in the whole life cycle of SFP based on ensuring its good pavement performance through applying fly ash, rubber particles, warm mixing technology, and recycled asphalt pavement (RAP) in SFP. It is observed that after the cement in the cement-based grouting material is replaced and modified with fly ash and rubber particles, the energy consumption and emission of SFP in the whole life cycle are significantly reduced. Compared with the gain effect of energy saving and emission reduction brought by cement replacement, the gain effect of environment-friendly modification of asphalt concrete matrix skeleton is in general. In particular, the application of RAP with high content will instead increase the energy consumption and emissions of SFP in the whole life cycle. At the same time, it is also found that the fatigue resistance of SFP has a significant impact on its energy consumption and emissions. It is a crucial method to reduce the energy consumption and emission of SFP in the whole life cycle to replace and modify the cement in the cement-based grouting materials by using environmentally friendly materials or technologies such as fly ash and rubber particles, and to guarantee or improve the performance of SFP. [ABSTRACT FROM AUTHOR]

[Display omitted] • The performance of the mixtures is influenced by the type of recycling agents. • WMA additive has a positive effect on performance of mixtures without RAP. • At intermediate temperature, RAP lowers the flexibility index. • RAP has a positive effect on rutting and moisture damage resistance of mixtures. • Performance interaction diagram approach should be included in designing mixtures. This research aims to use a balanced mix design (BMD) approach to investigate the effect of recycling agents (RAs) and an anti-stripping agent on the mechanical properties of warm-mix asphalt (WMA) containing different levels of reclaimed asphalt pavement (RAP). The BMD used three RAs (aromatic extract, triglycerides and fatty acids, and tall oil), an amidoamine WMA additive (PAWMA®), and an anti-stripping agent (Zycotherm®). The Dynamic Creep (DC), Indirect Tensile Strength (ITS), and Semi-Circular Bending (SCB) fracture tests were respectively used to evaluate the rutting, moisture susceptibility, and cracking resistance of mixtures. In addition, two-dimensional and three-dimensional (2-D and 3-D) performance interaction diagrams were developed as typical approaches for the BMD of asphalt mixtures. For mixtures with RAP, the results indicated that the aromatic extract and tall oil RAs decreased the moisture susceptibility, while triglycerides and fatty acids increased the moisture susceptibility. In addition, the RAs generally decreased the rutting resistance of mixtures while they increased the cracking resistance. This effect was more noticeable in the mixtures treated with triglycerides and fatty acids. The results also showed that introducing PAWMA® and Zycotherm® to the mixtures improved their resistance to moisture damage, cracking, and rutting. [ABSTRACT FROM AUTHOR]

In this study, comprehensive tests were carried out to assess the properties of asphalt binder and corresponding mixtures. The Marshall compaction tests of warm-mix and hot-mix styrene-butadiene-styrene (SBS) modified mixtures at various temperatures were performed. During plant simulated Marshall compaction tests, parameters including the moisture loss of aggregates were considered. Then, construction temperatures at various stages were recommended. Finally, the test sections in tunnels were paved and evaluated. The results show that 3% Sasobit is the optimum additive content. It is also determined that there is a 15 °C difference in compaction temperature between the traditional method and mixing plant method. Decreasing the heating temperature of aggregates does not impact the release of moisture. The field test sections show that the recommended compaction temperatures and other production temperatures for WMA are acceptable. [ABSTRACT FROM AUTHOR]

The use of foamed asphalt binder to produce warm-mix asphalt has increased significantly during the past few years. It is recognized that (1) foaming characteristics of the binder influence the workability of the asphalt mix, and (2) different asphalt binders tend to foam differently with all other factors being the same. The causes for the latter are relatively less explored and is the focus of this paper. The research reproted in this paper investigated the influence of the properties of asphalt binder on its foaming characteristics. A physical model for expansion of asphalt binder foam based on foam physics was used to quantify the effect of water content, temperature, surface tension, and liquid additive (through its effect on surface tension) on the expansion ratio of asphalt binder foam. Analysis of results demonstrates that the bubble size distribution (up to a certain limit) does not directly dictate the maximum expansion ratio of the asphalt binder foam. The analysis also shows that only a fraction of the water added to the binder is effective in creating the foam. The effective water content was strongly correlated with the surface tension of the binder, which was also substantiated by the solubility theory. Surface tension of the asphalt binder was also found to be strongly correlated to the stability of the foam. Foam characteristics of binders modified with additives also demonstrated that stability and expansion of foams can be significantly improved using carefully selected liquid additives. [ABSTRACT FROM AUTHOR]

This literature review paper presents the effects of a chemical warm mix additive, named Rediset on the rheological properties of asphalt binders, laboratory performance of asphalt mixtures, field behaviour of constructed road sections, energy consumption and air pollution, physicochemical properties of asphalt binders and behaviour of asphalt mortar. The rheological effects of Rediset on asphalt binder were evaluated from the viewpoint of very high temperature properties (viscosity of asphalt binder and workability of asphalt mixtures), high temperature properties (rutting resistance of asphalt binders and mixtures), intermediate temperature (fatigue behaviour) and also low temperature cracking properties. Other topics such as the mechanisms of temperature reduction by Rediset, storage stability of Rediset modified binders, moisture susceptibility, mix design issues, volumetric properties and economic benefits were also investigated. The information reported in this paper will help decision makers to appropriately select, apply and evaluate this warm additive type. In addition, researchers can identify gaps in existing knowledge for future research. [ABSTRACT FROM PUBLISHER]

• Bitumen aging increased the moisture sensitivity of asphalt mixture. • The NHL had a better performance in raising the specimens' TSR. • Long-term aging of bitumens increased their free energy of cohesion. • Long-term aging to the bitumens generally increased their cohesion free energy. • Long-term aging to the bitumens generally decreased their adhesion free energy. WMA due to its softer structure and high content of oils is more exposed to aging. Herein, the behavior of WMA in two states of control (unaged) and long-term aging in different compositions was examined and compared. The effect of factors contributing to WMA moisture sensitivity was minimized by utilizing suitable additives. Thermodynamic and mechanical approaches were adopted for this purpose. Two types of aggregates (granite and limestone) and bitumens (PG 58-22 and PG 64-16) were modified with nano-hydrated lime (NHL) and nano-calcium carbonate (NCC). The application of long-term aging increased the cohesion strength of both types of bitumen. Bitumen modification with the additives reduced the bitumen-aggregate debonding energy in the presence of water in control and long-term-aged specimens, which indicated the improved moisture damage resistance of the asphalt mixes By fitting the long-term aging results, the correlation coefficients between the indirect tensile strength ratio and free debonding energy increased from 0.6 to 0.7 in the first, and 0.8 to 0.9 in the third and fifth cycles. Thus, increasing the freeze–thaw cycles led to a stiffer bitumen with greater contribution to bearing the applied load, thereby promoting the validity and precision of mechanical and thermodynamic test results. [ABSTRACT FROM AUTHOR]

A number of completed or ongoing studies on warm-mix asphalt (WMA) and steel slag (SS) asphalt mixtures have been conducted all over the world. Moisture damage is one of the major concerns for both WMA and SS asphalt mixtures. This paper presents the results of a laboratory study aimed at verifying moisture susceptibility of WMA mixtures containing SS aggregates. The physical, chemical, and mechanical properties of aggregates and binders were evaluated to identify their effects on moisture susceptibility of asphalt mixtures. The moisture susceptibility of the asphalt mixtures was also evaluated by four different methods, including Marshall Stability Ratio, Resilient Modulus Ratio, Tensile Strength Ratio and Fracture Energy Ratio. The results generally indicated that use of coarse SS aggregate in WMA mixtures enhances the resistance of asphalt mixtures to moisture damage. Hence, use of steel slag aggregate in production of WMA mixture is recommended. [ABSTRACT FROM PUBLISHER]

Warm mix asphalt (WMA) describes various technologies that allow asphalt mixtures to be produced at lower temperatures as compared to hot mix asphalt (HMA). WMA technologies also offer improvements in workability, cost, and environmental sustainability such as reduced fuel usage, greenhouse gas emissions, and wear and tear at plants, while enhancing worker health and safety conditions. These benefits, as well as the mechanical properties of WMA mixtures, need to be quantified and compared to that of HMA. The primary objective of this study was to evaluate the laboratory performance of plant-produced lab-compacted mixtures utilizing various WMA technologies. The secondary objective of this study was to compare WMA energy consumption cost and emission data to conventional HMA mixtures in terms of fuel/energy savings at the plant and in terms of CO and CO2 emissions. Three projects in Louisiana utilizing four different WMA technologies were considered in this study, yielding 11 mixtures total. Each project included a companion HMA mixture section to allow for direct comparison. Loose mixtures were obtained from trucks at the plant and compacted on-site in a mobile asphalt laboratory. Laboratory tests included dynamic modulus (|E*|), flow number (FN), loaded wheel tracking (LWT) test, indirect tensile (IDT) test, semicircular bend (SCB) test, thermal stress restrained specimen test (TSRST), and the Lottman moisture susceptibility test. Results indicated that WMA mixtures exhibit similar high and intermediate temperature performances in the laboratory as compared to HMA. On average, $1.61 of energy savings per ton of produced asphalt mixture was observed, along with a considerable reduction in air pollutants at the plant. However, the cost of additives and royalty fees would reduce the total cost savings from usingWMA. These benefits were observed without reduction in the mechanistic performance of the mix. [ABSTRACT FROM AUTHOR]

Oxidation of an asphalt binder affects the long term performance of an asphalt pavement, especially under thermal and/or ultraviolet (UV) radiation conditions. The objective of this study is to investigate the rheological behaviors of various WMA binders after long term UV aging and conventional PAV aging procedures. The following rheological properties were tested and evaluated in this study: complex shear modulus, phase angle, elastic modulus, viscous modulus at an intermediate service temperature, and deflection, stiffness, and m -value at a low temperature. The experimental design included four asphalt binder sources (two grades); four WMA additives and control. Two aging methods of UV and PAV aging were utilized and a total of 40 binders were tested and evaluated. The test results indicated that UV and PAV aging procedures are significantly affected by asphalt binder source and grade. In addition, WMA additives generally have no influences on rheological properties of UV and PAV aged binders. Moreover, the differences in deflection, creep stiffness, and m -values of UV and PAV aged binders are generally not affected by their grade, source and WMA additives. Therefore, UV aging procedure used in this study may be an effective method in investigating rheological characteristics of WMA binder after a long term aging process. [ABSTRACT FROM AUTHOR]

Road transport is the most prevalent mode of transport in our country. However, large sections of our roads still suffer from congestion, inadequate pavement thickness and road safety hazards. Significant segments of population in hilly and tribal areas do not have all weather road accessibility. CSIR-Central Road Research Institute (CRRI), New Delhi has a crucial role to play in the road development programmes being undertaken by the government. Over the years, CRRI has developed many new techniques and solutions to problems affecting road sector. Notable achievements include urban road traffic and air pollution study, techniques for usage of waste materials, safety audits for various sections of national highways, traffic and transportation studies of metropolitan cities, bridge design and rating, providing solutions to premature pavement failures across the country, ground improvement, landslide problem mitigation, etc. The present article provides a glimpse of activities of CRRI and summarizes significant achievements during 2013-14. [ABSTRACT FROM AUTHOR]

As part of the research to evaluate the Warm-Mix Asphalt (WMA) performance for use in Korea, an extensive testing program has been conducted on the warm-mix asphalt technology that is newly developed in Korea, along with Hot Mix Asphalt (HMA). This research program consists of Accelerated Pavement Test (APT) and laboratory test. This paper presents the rutting and fatigue performance test results of both WMA and HMA. The rut development due to trafficking loading was evaluated using APT with 8.2 ton loading at 40°C temperature. The transverse profile was measured periodically at each point per test section as a function of mixture types. In order to investigate the fatigue performance, APT applied trafficking loading under wet and dry condition. The very stiff base is likely to complicate the planned fatigue cracking test, in that a huge number of APT repetitions will be generally required before any distress occurs. In this study, therefore, the fatigue test was conducted at 20°C with adding water into the aggregate base layer to accelerate the distress after the given trafficking loading. Cores were taken to be tested in the laboratory after construction of the test track as well as after completion of APT testing on and off the wheel path. The air voids were measured for all cores and dynamic modulus test and fatigue test in indirect testing mode were conducted. Based on the limited data obtained from this study, it is concluded that WMA mixture performs comparable to HMA mixture in terms of rutting and fatigue resistance. [ABSTRACT FROM AUTHOR]

The environmental concerns of global warming and energy consumption are among the most severe issues and challenges facing human beings worldwide. Due to the relatively higher predicted temperatures (150-180 °C), the latest research on pavement energy consumption and carbon dioxide (CO 2 ) emission assessment mentioned contributing to higher environmental burdens such as air pollution and global warming. However, warm-mix asphalt (WMA) was introduced by pavement researchers and the road construction industry instead of hot-mix asphalt (HMA) to reduce these environmental problems. This study aims to provide a comparative overview of WMA and HMA from environmental and economic perspectives in order to highlight the challenges, motivations, and research gaps in using WMA technology compared to HMA. It was discovered that the lower production temperature of WMA could significantly reduce the emissions of gases and fumes and thus reduce global warming. The lower production temperature also provides a healthy work environment and reduces exposure to fumes. Replacing HMA with WMA can reduce production costs because of the 20-75% lower energy consumption in WMA production. It was also released that the reduction in energy consumption is dependent on the fuel type, energy source, material heat capacity, moisture content, and production temperature. Other benefits of using WMA are enhanced asphalt mixture workability and compaction because the additives in WMA reduce asphalt binder viscosity. It also allows for the incorporation of more waste materials, such as reclaimed asphalt pavement (RAP). However, future studies are recommended on the possibility of using renewable, environmentally friendly, and cost-effective materials such as biomaterials as an alternative to conventional WMA-additives for more sustainable and green asphalt pavements.

The tensile strength (St) of warm-mix asphalt (WMA) and hot-mix asphalt (HMA) concretes were measured by indirect tensile strength test at 25, 5, -5, -15, -2 5 and -35°C. Fracture toughness (Tu) was calculated from each of the St test curves. Two WMA additives and two polymer modifiers were used to produce WMA mixtures at 135°C in the laboratory. All asphalt concretes evaluated in this study showed St increase by temperature decreases, peaking at -15°C or -25°C, then decreasing with further lowering of temperatures. The St values of WMA mixtures were observed to be higher than those of HMA mixtures in most cases at all low temperatures evaluated in this study. After being subjected to differential thermal contraction damage at -15 and/or -20°C, most of the WMA mixtures showed higher St than HMA mixes at severely low temperatures ( -2 5 and -35°C). Therefore, it was concluded that the WMA mixtures had stronger St than HMA mixtures at low temperatures when prepared with the same low-temperature PG binders, even though they were produced at a lower aggregate-heating temperature. [ABSTRACT FROM AUTHOR]

In recent years, a new group of technologies has been introduced in the United States that allow producing asphalt mixtures at temperatures 30 to 100°F (16.7-55.6°C) lower than what is used in traditional hot-mix asphalt (HMA). These technologies are commonly referred to as warm-mix asphalt (WMA). From among these technologies, foamed WMA produced by water injection has gained increased attention from the asphalt paving industry in Ohio since it does not require using costly additives. This type of asphalt mixture is advertised to have better workability than traditional HMA mixtures. However, limited research has been conducted to validate this claim. In this study, a new device was designed and fabricated to evaluate the workability of foamed WMA mixtures and compare it to that of HMA mixtures. Two asphalt binders (PG 70-22 and PG 64-28), two aggregate types (limestone and crushed gravel), and two nominal maximum aggregate sizes (12.5 and 19.0 mm) were used in this study. The test results showed that foamed WMA mixtures are more workable than HMA mixtures, which was attributed to the lower asphalt binder absorption observed for the foamed WMA mixtures. Another factor that might have contributed to the improvement in workability for the foamed WMA mixtures is the presence of vapor pockets entrapped within the foamed asphalt binder that keeps the binder slightly expanded and reduces its viscosity. For both foamed WMA and HMA mixtures, better workability was obtained for PG 64-28 than for PG 70-22, and for the 12.5-mm nominal maximum aggregate size than for the 19.0-mm nominal maximum aggregate size. HMA mixtures prepared using crushed gravel had better workability than those prepared using limestone aggregates. However, foamed WMA mixtures prepared using limestone aggregates had better workability than those prepared using crushed gravel, which indicates that aggregate type affects foamed WMA mixtures differently than HMA mixtures. [ABSTRACT FROM AUTHOR]

When the same class performance graded (PG) binders are used, the asphalt mixtures using the same aggregate and gradation are expected to perform similarly whether they are the hot-mix asphalt (HMA) or warm-mix asphalt (WMA). In this study, HMA and WMA mixtures with the same class PG binders were used to compare their performance. Two high-temperature (60°C) rut-related properties were evaluated, the wheel tracking (WT) and the strength against deformation (SD). One ambient-temperature (25°C) property, the indirect tensile strength (St), was also evaluated. The performance grades of normal (unmodified) and modified binders for all WMA and HMA mixtures were 64-22 and 76-22, respectively. According to study results, the modified WMA mixtures, which were short-term aged at 135°C, did not show high enough SD and WT resistance at 60°C than the HMA mixtures prepared using the same class PG binders, 76-22. However, the same WMA mixtures were found to be similar to or better than HMA mixtures in St. Therefore, it was found that tensile strength of WMA mixtures was not inferior to HMA at ambient temperature. However, rut-related properties of modified WMA mixtures were observed to be inferior to the same PG HMA mixtures at high service temperature. [ABSTRACT FROM AUTHOR]

This study experimentally characterized the mechanical properties of warm-mix asphalt (WMA) prepared with two chemical additives: Evotherm 3G and Rediset LQ-1106, using laboratory-mixed and laboratory-compacted (LMLC) specimens. A conventional stone matrix asphalt (SMA), widely used in expressway overlay projects in the Chicago area, was selected as the control mixture. Two warm SMA mixtures were prepared by adding 0.5% Evotherm 3G and 0.5% Rediset LQ-1106 by weight of binder, respectively. The performances of the control SMA, Evotherm SMA, and Rediset SMA were evaluated and compared through extensive laboratory testing, including complex modulus, loading wheel track, indirect tension, and semi-circular beam at various curing time periods after compaction. This study concluded that both warm SMA mixtures provided slightly lower tensile strengths and complex moduli than the control SMA. However, the rutting and fracture resistance potentials of the two warm SMA mixtures were relatively similar to that of the control SMA. The curing time effect on the performance of the two warm SMA mixtures varied depending on the material property measured as well as the additive type. A strong correlation between strength gaining and curing time for the two warm SMA mixtures could not be concluded. [ABSTRACT FROM AUTHOR]

Long-term thermal and ultraviolet (UV) aging procedures of asphalt mixtures are complicated, but can be simulated in the laboratory. The objective of this study was to investigate the influence of long-term thermal and UV aging on foamed warm-mix asphalt (WMA) mixtures. Rut resistance, indirect tensile strength (ITS), deformation, dissipated elastic energy, and fracture energy were measured for all mixtures. The experimental design included two aggregate sources; three aging states (unaged, thermal and UV aging); one water-bearing WMA additive and water foaming technology; two PG 64-22 binders, and three air void contents (2, 4, and 7 %). A total of 24 mixtures were evaluated and 144 specimens were made and tested in this study. The test results indicated that thermal and UV aging procedures had limited contribution in improving the rut resistance of a mixture as air void content was low. Unaged samples had the highest ITS values amongst three aging states while UV aged samples had the lowest. In addition, UV aged mixtures generally had greater dissipated energy than thermal aged mixtures regardless of foaming technology, aggregate source, and air void. Moreover, the foaming technology might reduce the stored elastic energy of the mixture due to additional water or released water from water-bearing additive. Furthermore, UV aging generally reduces the fracture resistance of an asphalt mixture than standard thermal aging. In addition, when using WMA foaming technology, aggregate source affects the fracture resistance of the asphalt mixture. [ABSTRACT FROM AUTHOR]

• The influence of thermal ageing on an isocyanate-modified bitumen was evaluated from a chemo-mechanical perspective and compared to unmodified and SBS-modified bitumen. • Lower production and construction temperature was simulated in a laboratory setting to study the influence on the chemo-mechanical properties of the different variants. • ATR-FTIR analysis was used to evaluate thermal ageing of unmodified and modified bitumen from a chemical perspective. • Different rheological tests were done to evaluate the effect of thermal ageing on a broad frequency and temperature range. Asphalt modification has been a good way to improve and prepare pavements to bear increasing traffic loads and temperatures; however, it is important that the additives used have a positive impact throughout the entire life cycle of the pavement. Since the performance enhancing capabilities of isocyanate-bitumen modification have already been documented, in this study, the focus lies on the ageing behaviour of this novel additive from a chemo-mechanical perspective. The chemical oxidative ageing was studied using infrared spectroscopy (ATR-FTIR), while the mechanical/rheological ageing, on the other hand, was studied using different tests performed with the dynamic shear rheometer (DSR), such as BTSV, frequency-temperature sweeps and cryogenic stress tests. Five different samples of unmodified, isocyanate-modified and SBS-modified bitumen were submitted to standard and extended laboratory short and long-term thermal ageing, respectively. Since the isocyanate-based bitumen modification has shown to enable warm-mix asphalt production, one variant was subjected to a short-term ageing at a lower temperature to consider this aspect. From a chemical perspective, the ATR-FTIR measurements show that the isocyanate-modified bitumen produced a higher chemical ageing after short-term thermal ageing compared to the SBS modification. However, on the long-term, this effect disappears. On a rheological level, the different methods used suggest that the mechanical ageing of the isocyanate-modification is comparable to the SBS modification. Moreover, a lower short-term ageing temperature appears to have a benefit on the chemical ageing but not on the mechanical/rheological ageing. [ABSTRACT FROM AUTHOR]

Asphalt binder is generally easy to age in the field, especially under thermal and/or ultraviolet(UV) radiation conditions. Current asphalt performance evaluation system gives limited consideration to UV aging, especially, as using warm mix asphalt (WMA) technologies. The objective of this study is to investigate the influence of long-term UV aging on rheology of various WMA binders. The following rheological properties were tested and evaluated in this study: viscous flow, performance grade, creep and creep recovery, amplitude and frequency sweep tests. The experimental design included four asphalt binder sources and two grades; four WMA additives (Cecabase-RT, Evotherm, Rediset, and Sasobit) and control. A total of 20 binders were tested. The test results indicated that a UV aging procedure generally had obvious effect on the complex modulus and phase angle values of various UV aged WMA binders. Their viscosity values were generally different since the WMA additive or binder source played a key role. Moreover, creep and creep recovery generally showed a similar trend for various WMA binders. Similarly, the amplitude and frequency sweep values exhibited a similar trend for various WMA binders but these values were different for various binder sources and grades. Therefore, it is necessary to explore the rheological properties of WMA binders after a longterm UV aging procedure in the lab. [ABSTRACT FROM AUTHOR]

A laboratory investigation was carried out to study the effects of various compaction temperatures on moisture susceptibility and rutting resistance of warm-mix-asphalt (WMA) mixtures containing moist aggregates using a foaming technology. The experimental design included two aggregate moisture contents (0 and by weight of aggregate dry mass), one lime content (1% lime by weight of dry aggregate), two foaming water contents (2 and 3%) with control, and two aggregate sources. The major properties, such as the gyration number of various samples, indirect tensile strength (ITS), tensile strength ratio, rut depths of dry and conditioned specimens, and deformation (flow), were measured for all mixtures. The test results indicated that the aggregate source significantly affected the ITS and rutting resistance regardless of the foaming water content, compaction temperature, and aggregate moisture content. In addition, mixtures from moist aggregate had lower gyration numbers regardless of aggregate type, foaming technology, and compaction temperature. Moreover, the ITS values of foamed mixtures containing moist aggregate increased as the compaction temperature increased. Furthermore, the rut depths of all the dry and wet mixtures slightly increased as their compaction temperatures decreased regardless of the aggregate moisture content, foaming water contents, and aggregate type. A compaction temperature below 102°C (215°F) generally had no noticeable aging (2 h) effects on the mixture and did not significantly increase the rutting resistance of these WMA mixtures. [ABSTRACT FROM AUTHOR]