Base Binder Research Articles

Mechanical performance and statistical analysis of natural and synthetic zeolite-warm mix asphalt as a function of compaction efforts

The compaction effort of mixes should be studied with caution since it significantly influences the mixtures' performance. A laboratory evaluation of warm mix asphalt (WMA) including synthetic zeolite (SZ) and natural zeolite (NZ) was conducted in this study. Marshall properties, tensile strength ratio, indirect tensile strengths at 25 and 60 °C, resilient modulus at 25 °C, and creep compliances at 40 °C were all examined. The NZ and SZ binders were produced by mixing one base binder (40/50 penetration grade) with 5% NZ and SZ binder components by weight. The 90 specimens were produced using the Marshall compactor at three different compaction efforts (35, 50, and 75 blows/face). Statistical analysis was conducted to examine the behavior and outcomes of asphalt binders. The results showed that (1) Both NZWMA and SZWMA combinations require 35 blows/face compaction effort to meet the minimum criteria of 8 kN stability, 2–4 mm flow, 85% tensile strength ratio, 14% VMA, and 448 kPa unconditioned tensile strength; (2) The production of NZWMA mixtures saves more time and fuel in the field than SZWMA mixtures while meeting the Marshall properties, creep performance, and moisture susceptibility at 35 blows/face compaction effort; and (3) A general trend of the Marshall, creep compliance, tensile strength, and resilient modulus performance as a function of compaction effort was observed for the NZWMA and SZWMA mixes used in this study.

Laboratory performance and construction challenges for plant produced asphalt mixes containing RAP and RAS

In this study, four plant-produced asphalt mixes were considered to evaluate the performance and construction challenges of mixes containing RAP/RAS. Also, asphalt mixes were collected at two different plant-production times for each mix type to monitor the performance variability between lots. A softer base binder (PG 58–22) was used for mixes with RAS compared to the base binder (PG 64–16) used for the control mix (no RAP or RAS) and the mix with only RAP. Use of small dosages of rejuvenators and the softer binder in the RAS mixes were found to show similar performance compared to the control mix with no RAP or RAS. The results obtained from the extracted binders of these mixes indicate that mixes with RAP and RAP/RAS are expected to show higher rutting resistance and slightly lower low-temperature cracking resistance, also shown in the mix rutting and fracture cracking tests. A similar fatigue life was observed for all mixes at low strain levels in the Four-Point Beam test. However, the mix with both RAP and RAS was found to show better fatigue life at high strain levels. Similar performance test results were observed between different lots of the same mix type for most cases. Finally, there were no problems with field mixing, compaction, or finishing of the mixes containing RAP and RAP/RAS.

Zeolite-Like Warm-Mix Asphalt Additive: Dosage Optimization Based on Asphalt Binder Characterization

Abstract The major objective of this research was to augment the temperature reduction characteristics of the recently developed sodium aluminate tetraethyl ammonium hydroxide montmorillonite (STEAM) warm-mix asphalt (WMA) additive by optimizing 8 dosages of 20 STEAM variants mixed with one viscosity graded-30 base asphalt binder. As the first step in the optimization process, a series of molar combinations of sodium aluminate and tetraethyl ammonium hydroxide were blended with constant concentrations of weights of montmorillonite (MMT) and water. The Fourier transform infrared (FTIR) spectroscopy test was performed on all the 20 STEAM variants to derive the hydroxyl functional groups and understand if they have potential in reducing the mixing and compaction temperatures of the STEAM-modified asphalt binder. The FTIR results indeed indicated that hydroxyl bonds increased with increasing MMT content, as a consequence of MMT releasing itself when mixed with the base asphalt binder. Next, the STEAM additives were mixed with the base binder at 8 dosages with 2 molar ratios covering 20 STEAM-modified asphalt binders on which penetration, softening point, and rotational viscosity tests were performed mainly to establish the ASTM Ai-VTSi relationships. Depending on the combination of molar ratio and dosages, the STEAM-modified asphalt binders demonstrated a decrease of about 3°C–8°C of mixing and compaction temperatures. Furthermore, the STEAM additive that exhibited highest reduction in mixing temperature was blended with dense-graded aggregate gradation to produce a STEAM-modified asphalt mix, which reduced the production temperature by 10°C based on the equivalent mixture performance criterion while also demonstrating stiffness performance similar to that of a control mix. Overall, the optimized indigenous STEAM WMA additives proved to be water-containing, zeolite-like products that have immense capacity in minimizing the working temperatures, albeit further studies should focus on tapping the full potentiality of several STEAM combinations to render the products as globally acceptable “green” paving materials.

Low-Temperature Fracture Performance of Polymerized Sulfur Modified Asphalt Concrete Mixtures

In this research, asphalt concrete (AC) mixtures modified by polymerized Sulfur were prepared. PG58-22 bitumen was used as the base binder for the mixtures along with crushed siliceous aggregate. The base binder was replaced by 20%, 30%, and 50% ratios with polymerized Sulfur in the modified mixtures while the reference mix was fabricated with 0% binder replacement. Single edge notched-beam fracture tests (SE(B)) were carried out in a temperature range of 0 °C to-20 °C on the AC beam specimens. Load-displacement curves were obtained from the experiments and the fracture energy of the mixtures could be determined. It was revealed that modifying the mixtures with polymerized Sulfur could improve the load bearing of the beam specimens as higher peak load values were recorded at fracture. However, fracture failure of the AC beams occurred at lower values of displacement addressing further embrittlement of the mixtures due to replacement of the base binder. Higher contents of polymerized Sulfur in the mixtures resulted in higher magnitudes of fracture energy as a general trend in this research addressing an improved resistance to low-temperature cracking.

Rheological performance of bitumen mixed with laboratory simulated polymerized RAP binders

Researchers have mostly used three artificial aging techniques, namely pressure aging vessel (PAV) binder aging, compacted mix aging (CMA), and loose mix aging (LMA) to simulate recycled asphalt pavement (RAP) binder in the laboratory. RAP binder (RAPB) simulated using different techniques will differ in characteristics and may affect the performance of the base binder differently. Which may affect the parameters used for blending and recycling, such as the selection of base binder, rejuvenator dosage, etc. Therefore, in this study, three RAP binders, namely RAPB-P, RAPB-C, and RAPB-L, were simulated from a polymer modified binder (PMB) with 3.5% SBS content, using PAV aging (100 °C, 20 hrs, 2.1 MPa), CMA (85 °C, 5 days) and LMA (85 °C, 8 days), respectively. These polymerized RAPBs were added to an unmodified binder (AC 30) at three proportions: 15 %, 25 %, and 40 %. These RAPB and AC 30 blends were characterized in terms of their dynamic viscosity, mixing and compaction temperature, and high temperature performance grade (PG). Superpave rutting factor (|G*|/sin δ) and multiple stress creep and recovery (MSCR) test parameters were used to evaluate the rutting performance of the RAPB blended AC 30 binders. Further, resistance to yielding and elastic recovery values were evaluated using the binder yield energy test (BYET). The test results suggested that all three RAP binders affect the performance of the AC 30 binder differently, which was also confirmed by statistical analysis using one-way ANOVA. From MSCR and BYET test results, it may be stated that RAP binder simulated from standard PAV aging may mislead in predicting the high and intermediate temperature performance of AC 30 binder with RAPB. Overall, the present study is helpful for asphalt researchers and practitioners to understand how the selection of different defined aging strategies affects the performance of aged recycled PMB with unmodified base binder.

Rutting Resistance Evaluation of Highly Polymer-Modified Asphalt Binder and Mixes Using Different Performance Parameters

This study focused on evaluating the rutting performance of three different highly polymer-modified asphalt (HiMA) binders (i.e., O, T and B) using binder-based [i.e., multiple stress creep recovery (MSCR) and force ductility (FD)] and mix-based [flow number (FN) and Hamburg wheel tracking test (HWTT)] rutting performance tests. The binder-based rutting indicators were compared with mix rutting performance to determine a parameter that can help in the correct prediction of HiMA rutting resistance. In addition, the study looked into application of a simple performance test, the indirect rutting tolerance index (IDEAL-RT), for HiMA mix rutting prediction. The MSCR test revealed different rankings of recovery at 0.1- and 3.2-kPa stress levels. Moreover, the T and B binders did not satisfy the stress sensitivity criteria (Jnr_difference) of Max 75%. The force ductility tests revealed that the peak force observed for polymer network phase in HiMA was significantly higher than base binder stiffness, which is in contrast with force distribution in polymer-modified binders (PMBs). The mix rutting resistance ranking (O>T>B) was similar in all the tests (i.e., FN, HWTT, and IDEAL-RT). Although IDEAL-RT can be used to compare the rutting resistances of HiMA mixes, detailed future work is required to establish its acceptability in comparing various types of mixes and the minimum requirements of RTIndex. The comparison between binder and mix rutting indicators demonstrated that MSCR testing on binder at stress levels of 6.4 kPa and higher can be used to predict the rutting resistance of HiMA binders. Parameters like slope and cohesion energy and a newly introduced parameter—work done for polymer activation (WPA)—from FD tests can be used to determine the polymeric phase dominance in HiMA binders. Overall, this study provides pavement stakeholders with a framework for rightly predicting the rutting resistance and polymeric phase dominance of HiMA binders and mixes using MSCR, FD, and IDEAL-RT tests.

A bibliometric analysis and review on the performance of polymer-modified bitumen

The addition of polymer to a base binder has been documented as a successful approach in terms of improving physical and rheological properties of the base bitumen. However, the main drawbacks of polymer-modified bitumen are incompatibility and degradation of polymer due to aging. This article aims to introduce a bibliometric analysis and review on modifying bitumen with polymers. Additionally, this article intent to highlight the significant gaps and recommendations for future work. Furthermore, another objective of this article is to provide a worth attempt regrading reducing the negative impact of polymer’s drawbacks on the performance of polymer-modified base binder. The findings of this article demonstrated that the test of storage stability for polymer-amended bitumen should be modified, in which the softening point of aluminum tube centerpiece should be measured to introduce a better evaluation for the storage stability of polymer-amended bitumen. In addition, the effects of kinetic factors (mixing sequence, viscosity of blend, shear rate, and time of mixing) on the compatibility of polymer-amended bitumen should be investigated. Moreover, the addition of compatibilizers and stabilizers to polymer-modified binder is recommended to improve compatibility and reduce the effect of aging on degradation of polymer.

Performance Evaluation of Long-Term Laboratory-Aged Asphalt Mixtures Containing Different Molecular Structures of SBS Copolymers

The current study emphasizes the impact of styrene-butadiene-styrene (SBS) molecular structures on the extent of performance deterioration in asphalt mixes after short-term and long-term laboratory aging. First, modified binders were prepared using linear (L-SBS), branched (B-SBS), high vinyl (HV-SBS), and di-block (DB-SB) SBS copolymers, and consequent asphalt mixes were fabricated using these modified binders. The influence of aging on the asphalt mixture performance has been evaluated through Cantabro mass loss, fracture properties, fatigue, and rut resistance behavior. Results showed that irrespective of the type of SBS polymer in the binder, the short-term aging (STA) of asphalt mixes had an insignificant effect on their performance properties. However, a substantial drop in all mix performances was observed after long-term aging (LTA) with L-SBS and B-SBS modified binders due to the degradation of the polymer chains. Mixes prepared with L-SBS and B-SBS copolymers depicted higher variation in the aging index after LTA than their counterparts and were also unable to protect the base binder from stiffening. In contrast, HV-SBS and DB-SB generate significantly lower temperature susceptibility in the asphalt mixture due to higher vinyl content (≥30%), i.e., location of the C=C group as the side chain in the butadiene segment. Fourier-transform infrared spectroscopy (FTIR) results reveal that the increase of carbonyl and sulphoxide compounds, and the lowering of polybutadiene compounds validate the adverse effect of LTA on L-SBS and B-SBS copolymers. On the contrary, such behavior was not reflected in HV-SBS and DB-SB copolymers. Thus, the current study presents the major limitation of using branched and linear SBS polymers having comparatively lower vinyl content, and recommends the mandatory use of high-vinyl SBS copolymers for ensuring enhanced long-term performance.

Evaluating the Rheological Behavior of Bone-Glue Modified Asphalt

Worldwide, asphalt is one of the most widely utilized materials in pavement constructions. The loading and temperature conditions have a significant impact on the asphalt behavior. Various additives have been used over time to enhance asphalt's performance at both high and low temperatures. As the weather in Pakistan is hot for the majority of the year, flexible pavements benefit from the use of asphalt binders that are resistant to the effects of high temperatures. Researchers have attempted to enhance the asphalt mixture's high-temperature performance by adding acids, polymers, fibers, and extenders. In this study, bone glue (BG), a biomaterial produced from animal waste, was added to a base binder in concentrations of 2%, 4%, and 6% by weight. The BG is made in an environmentally responsible manner. It is a natural material that saves money and does not harm the environment. It also results in a long-lasting asphalt composite. Testing methods, such as consistency and rheology analysis, were used to determine how much of an impact bone glue had on asphalt binder. The results demonstrated that the asphalt binder's high-temperature performance was significantly enhanced by the incorporation of bone glue. Rheological testing revealed that a binder concentration of 6% BG by weight produced the best results.

Temperature susceptibility of asphalt binder modified with palm oil mill sludge

Modification of asphalt binder is continuously gaining interest as a result of the depletion of this non-renewable materials and their expensive price. There is a drive to use modifiers in asphalt including agricultural waste. In this study, palm oil mill sludge (POMS) was employed. The penetration grade of 60/70 as base binder incorporating with 1%,2%,3%,4% and 5% POMS were investigated for temperature susceptibility. These modified binders were tested for penetration, softening point, and viscosity. Subsequently, the penetration index (PI), penetration-viscosity number (PVN), activation energy (Ea) and viscosity-temperature susceptibility (VTS) were used to analyze the effect of POMS on the temperature susceptibility of asphalt binder. The results showed that the addition of POMS to the asphalt binder under unaged circumstances increased the penetration value from 66.56 dmm to 80.08 dmm and decreased the softening point from 49.25°C to 45.6°C for 4% POMS which indicates the softening effect of the asphalt binder. In contrast, following short-term ageing, the penetration value decreased as the softening point increased, showing that the modified asphalt binder stiffened after aging. According to the PI, PVN, Ea and VTS values of the modified POMS asphalt binder, the addition of POMS decreased its temperature susceptibility. Based on the ranking, 4% POMS was found as the best concentration of asphalt binder modifier. In conclusion, the use of appropriate amounts of POMS as an asphalt modifier is possible and provides a possible way to reuse POMS.

Experimental investigation of usability of modified asphalt binder with waste expanded polystyrene (EPS)

EPS (Expanded polystyrene) is widely used in construction and packaging industries. Unfortunately, EPS is not mostly recyclable because it might not be economically feasible to store, transport, and process EPS so that it becomes recyclable. Therefore, alternative waste management strategies are urgently needed. The main objective of this study is to experimentally investigate the potential use of waste EPS in asphalt binder modification. As part of this study, a base asphalt binder with a Penetration grade of 70/100 was modified with waste EPS in four different ratios (0%, 1.5%, 3% and 4.5%, by weight of asphalt binder). The modified asphalt binder specimens were tested based on several physical (penetration, ductility, softening points and viscosity) as well as rheological/Superpave binder grading system tests including Rolling Thin Film Oven (RTFO), Pressure Aging Vessel (PAV), Dynamic Shear Rheometer (DSR), and Bending Beam Rheometer (BBR). Based on the tests results, rheological and engineering properties of the modified asphalt binders were compared with the ones of the base binder so that effect of waste EPS addition on the properties of the base binder was evaluated; and how the Superpave binder grades of the modified binders were changed with the additions of waste EPS was discussed. It was found out that modifying asphalt binders with EPS provided them with a better rutting resistance at the expense of lowering their fatigue and low temperature cracking resistance. Overall, it could be concluded that waste EPS can be potentially used in the asphalt binder modification by paying special attention to these factors, and it should be noted that using waste EPS in the asphalt binder modification has many economic and environmental benefits.

Materials Optimization and Service Performance Evaluation of a Novel Steel Bridge Deck Pavement Structure: A Case Study

Although the double-layer pavement structure with a top layer of stone mastic asphalt concrete (SMAC) and a bottom layer of epoxy asphalt concrete (EAC) has been confirmed to have excellent overall performance in the laboratory, there is a lack of comparison and verification in practical projects. Hence, the utilization of the SMAC + EAC structure in this steel bridge deck pavement (SBDP) practical project and the clarification of its service performance are of significant importance for facilitating the promotion and application of this novel structure. This study relied on an SBDP reconstruction project in Ningbo, China. Indoor performance tests were used to determine the appropriate material compositions for SMAC and EAC. Subsequently, both ERS and SMAC + EAC pavement structures were paved in the project, and the service conditions of the different pavements after one year of operation were tested and compared. The results indicated that the epoxy SBS asphalt (ESA) binder prepared by substituting SBS-modified asphalt binder for the base binder, exhibited improved mechanical strength and toughness. The variation of modifier content significantly affected the high-temperature stability, low-temperature crack resistance, and moisture damage resistance of epoxy SBS asphalt concrete (ESAC) and high-viscosity SBS asphalt concrete (HSAC), while the gradation mainly influenced the skid resistance. The optimal contents of modifiers in ESA and HAS binders were finalized at 45 wt% and 11 wt%. After one year of operation on the trial road, the pavement performance of the SMAC + EAC structure had significant advantages over the ERS system, with all lanes having an SBDP quality index (SDPQI) above 90 and an excellent service condition. The successful application of the SMAC + EAC structure validated its applicability and feasibility in SBDP, which provided strong evidence for the further promotion of this structure.

Application of waste biaxially oriented polypropylene sandwiched graphene to enhance properties of asphalt mixes via a wet process

The global community is concerned about the environmental degradation caused by plastic waste, particularly Biaxially Oriented Polypropylene (BOPP) used in food packaging materials. Utilizing plastic in road construction can conserve energy, reduce pollution, and enhance the performance of asphalt mixes at high temperatures. Many research studies have inspected the impact of various types of plastic, such as LDPE, HDPE, LLDPE, and others, on the physical-rheological and chemical characteristics of the base binder. This study assesses how BOPP and Graphene Oxide (GO) work together to develop the performance of the base binder. The modified binder's physical-rheological and chemical structure was evaluated using different percentages of BOPP and Graphene oxide. Penetration, Softening Point, Rotational Viscosity, Dynamic Shear Rheometer (DSR), and temperature sweep tests were conducted to examine the modified binder's properties changes. The findings indicate that the combination of GO and BOPP significantly improved the physical–chemical and rheologic properties of the base binder. The trial rheological results for 0.4%, 0.5%, 0.6% of GO and 1.5%, 2.0%, and 2.5% of WBOPP (GWBOPP) modified bitumen demonstrate that the modification of the base binder with this combination improved its elastic capacity at higher temperatures and rutting resistance. These results suggest a positive correlation between the chemical-physical-rheological parameters.

Evaluating Self-Healing Behaviour of Asphalt Binders Modified with Phase-Change Materials, Polymers and Recycled Glass Powder.

The objective of this paper is to evaluate the fatigue resistance and self-healing properties of asphalt binders modified with different types of additives (Styrene-Butadiene-Styrene (SBS), Glass Powder (GP) and Phase-Change Materials blended with Glass Powder (GPCM)). Two base binders were used in this study: a PG 58-28 straight-run asphalt binder and a PG 70-28 Polymer modified with 3%SBS. Moreover, the GP was added to the two base binders at two different percentages of 3.5% and 5% by binder weight. However, the GPCM was added with two different percentages of 5% and 7% by binder weight. In this paper, the fatigue resistance and self-healing properties were evaluated using Linear Amplitude Sweep (LAS) test. Two different procedures were adopted. In the first procedure, the load was applied continuously until failure (without a rest period), whereas, in the second procedure, rest periods of 5 and 30 min were introduced. The obtained results of the experimental campaign were ranked based on three different categories: Linear Amplitude Sweep (LAS), Pure Linear Amplitude Sweep (PLAS) and modified Pure Linear Amplitude Sweep (PLASH). The addition of GPCM appears to positively impact the fatigue performance of both straight-run and polymer-modified asphalt binders. Furthermore, when a short rest period of 5 min was introduced, the use of GPCM did not appear to improve the healing potential. However, a better healing capacity was observed when the 30 min rest period was applied. Moreover, the addition of GP alone to the base binder was not beneficial in improving fatigue performance based on LAS and PLAS methods. However, there was a slight reduction in the fatigue performance based on the PLAS method. Finally, unlike the PG 58-28, the healing capacity of the GP 70-28 was negatively affected by the addition of the GP.

Physical Characterization of Modified Asphalt Binder with Differing Fly Ash Geopolymer Contents

Nowadays, the use of waste material product widely usedin the asphalt mixtures industry production duetoa cost-effective method of pavementconstruction that can decrease the consumption of natural resources and to reduce environmental pollution.This research aimed to investigate the possibility of using waste and by-product material namely fly ash geopolymer additive to influence the physical properties of asphalt binder. A series of asphalt binder laboratory tests were carried out to evaluate the properties of the 60/70 and 80/100 asphalt binder incorporating 3%, 5%, 7%, 9% and 11% of fly ash geopolymer additive. The physical properties of the binders were determined using the penetration, softening, penetration index, ductility, and rotationalviscosity respectively. The results indicated that, the fly ash geopolymer modified binder had improved the physical properties over base binder. The thermal susceptibility also improved by referring to the Penetration Index value.Overall research conclusions are that geopolymer application resulted in a potential enhancement of some of the properties of the asphalt binder and increase the performance of asphalt binder in the pavement application.

Emission of Volatile Organic Compounds in Crumb Rubber Modified Bitumen and Its Inhibition by Using Montmorillonite Nanoclay

Bitumen emits a large amount of volatile organic compounds (VOCs) during the production and construction of asphalt mixture, which can cause both environmental hazards and health risks. In this study, a setup was designed to collect the VOCs released by base and crumb rubber-modified bitumen (CRMB) binders and their composition was characterized by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Next, organic montmorillonite (Mt) nanoclay was added into CRMB binder and its inhibiting effect on the VOCs emission of the binder was investigated. Finally, the VOCs emission models for the CRMB and Mt-modified CRMB (Mt-CRMB) binders were established according to reasonable assumptions. The results indicated that the VOCs emission of CRMB binder was 3.2 times larger than that of the base binder. Due to its intercalated structure, the nanoclay can reduce the VOCs emission of CRMB binder by 30.6%. Especially, its inhibition effects on alkanes, olefins, and aromatic hydrocarbons were more significant. After finite element verification, the established model based on the Fick's second law can describe the emission behavior of CRMB and Mt-CRMB binders well. Overall, the Mt nanoclay can be used as an effective modifier to inhibit the VOCs emission of CRMB binder.

Characterizing the Aging and Performance of Asphalt Binder Blends Containing Recycled Materials

Abstract The aging of asphalt concrete is mainly governed by the aging of the asphalt binder, which is a naturally occurring organic hydrocarbon. Both chemical and rheological properties of asphalt binder are expected to change as aging continues. The pavement industry is increasing the use of different recycled materials in the construction and rehabilitation of flexible pavements to preserve natural resources, save costs, and reduce environmental emissions. The aged binder from recycled materials is expected to alter the binder properties and its aging characteristics in the new mix. In this study, 3 different virgin base binder types (PG 64-16, PG 58-22, and PG 70-10) and 7 different binder blends containing recycled binders (up to 100 % binder replacement) were subjected to different aging conditions. The rheological and chemical properties of these binders were characterized using a dynamic shear rheometer and Fourier transform infrared spectroscopy, respectively. It was found that the Glover-Rowe parameter distinctively captured the change in binder rheological properties with aging for the different binder blends. A good correlation (R2 value of 0.83–1.00) was observed between binder chemical and rheological properties. The source and performance grade of the base binder were found to govern the correlation between the rheological and chemical properties of the blended binder. Hamburg wheel tracking (for rutting and moisture sensitivity) and indirect tensile asphalt cracking test (for fracture) tests were conducted on asphalt mixes maintaining the same blended binder ratios. The laboratory mix performance parameters were found to correlate well with the properties of the blended binders. Therefore, properties of the blended binders can be an important source of information for predicting the performance of asphalt mixes containing recycled materials.

Comparing the performance of SBS and thermoplastics modified asphalt binders and asphalt mixes

This study comprehensively compares the conventional, rheological, morphological, and asphalt mix performance among SBS and several thermoplastics (TPs) modified binders. TPs modified binders (TP-MBs) may have modulus values similar to SBS modified binders (SBS-MBs), but several other critical properties were far inferior. Percent elastic recovery of ungrafted TP-MBs was < 10 percent, phase angle values were close to 80°, and the softening point was 15–20°C lesser than SBS-MBs. At intermediate and low temperatures, TP-MBs exhibited higher complex modulus values and increased the PG intermediate and low temperature. The presence of TP polymer even reduces the ductility compared to the base binder. Similarly, TP-MBs enhance the Marshall stability and rut resistance in mixes by 20–40 percent, but the improvement was not observed in moisture susceptibility, indirect tensile strength, and fatigue crack performance. Hence, analysis limited to the modulus of the MBs, Marshall stability, and rutting in mixes can falsely indicate that TPs can increase the overall performance of asphalt binders and mixes.

Chemical and mechanical analysis of field and laboratory aged bitumen

To predict the performance of bituminous products during their service life, an accurate simulation of the aging behaviour is required. Several laboratory methods are available, yet the correlation to field aging is mostly missing. In this study, an unmodified bitumen was exposed to laboratory aging with the Pressure Aging Vessel (PAV) using one to five aging cycles and the Viennese Binder Aging (VBA) method, followed by a comparison to a field sample of the same base binder. Measurements with the dynamic shear rheometer (DSR) and Fourier-transform-infrared (FTIR) spectroscopy showed that the field aging level could not be reached neither with VBA nor with multiple PAV cycles, but a better approximation compared to the standard aging procedure was achieved. The FTIR spectra displayed a high degree of correlation between the VBA and field aged sample, especially regarding carbonyl formation in the aromatic fraction and the intensity of the sulphoxide band in the resin and asphaltene fractions. Additionally, the VBA sample showed more similarities to the field sample regarding fluorescence excitation–emission maps. Although both laboratory aging methods are an improvement to the standard procedure, the VBA method allowed for a better qualitative simulation of the chemical properties of the investigated field sample.

Exploration of Curing Characteristics of Epoxy-Modified Asphalt

A study was conducted on epoxy-modified asphalt (EMA) diluted with two binders of a different chemical structure, to understand the effect of curing rates and long-term postcuring characteristics. Dynamic shear rheometer test results did not show a clear trend of curing time and dosage percentage impact for the two base binders; parallel-plate geometry may not be well-suited to study EMA because of the thermosetting properties of curing. The asphalt binder test (ABT) method was used to assess the effect on rheology of short-term and long-term curing. Analysis of the ABT data to date suggests that the binder source has a notable effect on the composite properties. The impact of long-term storage was also found to be dependent on the asphalt binder used. Findings from this study were also applied to two field binders; one was modified using styrene-butadiene-styrene polymer, and the other contained epoxy. Curing times were determined using the ABT test. The Dongre Workability Test (DWT) was also conducted on open-graded friction course mixes and the mix curing times were found to be significantly higher than those determined on the binders. A method based on DWT data to determine a “workability window” was also explored. The Strategic Highway Research Program (SHRP) sol-type binder AAG-2 was found to exhibit little to no reactivity with the epoxy modifier used in this study. The SHRP gel-type binder AAD-2, however, was found to be highly reactive. The short-term curing temperature was found to affect the rate of curing for base binder AAD-2. The curing rate was found to be highest at 165°C followed by 120°C, and the rate was at its slowest at 25°C. AAG-2 did not show any onset of curing at either temperature.