Neat Binder Research Articles

Investigation into possibility of rejuvenating aged asphalt binder using mustard oil

ABSTRACT Incorporation of high content of Reclaimed Asphalt Pavement (RAP) into fresh asphalt mixtures make them prone to thermal cracking and fatigue failure. Rejuvenators are usually recommended to overcome this problem by restoring the aged asphalt binder properties. This study aims to investigate the feasibility of using Mustard oil as a rejuvenator and to evaluate its effectiveness as a rejuvenator by determining the extent to which it restores the chemical and physical properties of aged asphalt binder extracted from RAP. The effect of Mustard oil on physical, rheological, chemical and thermal properties of aged asphalt binder was studied by employing Rotational Viscometer, Dynamic Shear Rheometer, Bending Beam Rheometer, Fourier Transform Infrared Spectroscopy, Thermogravimetric analysis, Gas-Chromatography-Mass Spectrometry and Rolling bottle equipment. Results indicated that Mustard oil effectively restores the properties of aged asphalt binder and can be used as a suitable rejuvenator. Ten per cent of Mustard oil is recommended as an optimum dose for rejuvenation of aged asphalt binder. This dose is based on restoring the RAP binder to match the properties of neat binder having PG64 and is specific to the stiffness of RAP material being used.

Investigating the Crack Initiation and Propagation of Asphalt Binder in Linear Amplitude Sweep Test

The linear amplitude sweep (LAS) test has been widely accepted for estimating the fatigue resistance of asphalt binders in the last 10 years. This paper proposes a fracture mechanics–based analytical approach for crack initiation and propagation characterization in the LAS test, aiming to more precisely explore the binder crack growth and failure mechanism. Seven unmodified neat asphalt binders and one styrene-butadiene-styrene (SBS) polymer-modified binder are selected in this study. The crack length (a), rate of cracking (da/dN), stress intensity factor (K), and energy release rate (G) are the fundamental parameters for the data interpretation approach proposed in this paper. Experimental and analysis results demonstrate that the energy-based failure definition (either from continuum damage mechanics or fracture mechanics) should be utilized to detect the material-dependent failure occurrence in LAS test. The fracture behavior of asphalt binder in the LAS test follows the two-phase crack growth (TPCG) model in terms of the crack initiation and crack propagation. The crack propagation phase further consists of stable crack growth and unstable crack growth. It is found that the fatigue performance of asphalt binder is intrinsically governed and dominated by its resistance to the crack propagation. The SBS binder in this study clearly displays slower crack propagation behavior than other neat binders. Additionally, the traditional fatigue life can also be divided into the crack initiation life and crack propagation life, which is promising to clarify the specific modification contribution to binder fatigue resistance. The two critical crack lengths of initiated crack and propagated crack for a given asphalt binder are found to be correlated to each other, indicating the potential links between the binder crack initiation and propagation behaviors.

Evaluating the properties of zinc production wastes as filler and their effects on asphalt mastic

This study evaluated four types of zinc production waste and limestone powder to be used as filler in asphalt mixtures. The properties of the fillers, asphalt mastic and mixtures made by the fillers were investigated. Only the results for fillers and mastics are provided. The physical and chemical properties and morphology of waste fillers, namely cobalt cake, leach cake, nickel cake, and zinc ash, as well as the limestone powder, as control filler, were examined. The moisture content, particle and bulk density, methylene blue value (MBV), Rigden voids (RV), pH, chemical compositions, morphology, hydrophobicity, size distribution, solubility in water, and specific surface area of the fillers were evaluated. Also, using a constant volumetric filler to binder ratio, asphalt mastics were made and their softening point, ductility, penetration grade and rheological properties were measured and compared with neat binder. Evaluation of the properties of fillers showed that the fillers can be potentially used in asphalt mixtures. Zinc ash had comparable and even better properties than the control filler. In terms of hydrophobicity, solubility in water and moisture content, the best performance belonged to zinc ash, followed by limestone, nickel, cobalt, and leach cake, respectively. Leach and cobalt cake showed to be hydrophilic fillers. The lowest MBV was found for the zinc ash, followed by limestone, nickel, leach and cobalt cake. The highest RV was found for the leach cake, and lowest for zinc ash filler. The fillers have different levels of stiffening effect on the mastic. In terms of temperature susceptibility using the softening point test results, the lowest sensitivity was obtained for zinc ash followed by cobalt cake, leach cake, limestone, and nickel cake. However, penetration and DSR test results revealed that the highest stiffening effect was obtained using zinc ash followed by cobalt cake, nickel cake, limestone, and leach cake. The stiffening effect of the fillers can be described by the morphology of filler particles; however, RV cannot be directly related to the stiffening effect of the fillers.

Evaluation of Multiple Stress-Creep Recovery Test on Alaskan Asphalt Binders

Although the multiple stress creep recovery (MSCR) test has shown its superiority in predicting rutting resistance of asphalt binders, concerns have been raised regarding the testing protocol and procedures. To evaluate the rutting resistance and investigate the suitability of the standard MSCR test method for Alaskan binders, nine typical Alaskan asphalt binders from three different suppliers were collected from paving projects and tested using MSCR tests with four different testing protocols and procedures. The results indicated that the modified binders had better rutting resistance than the neat binder regardless of performance grade (PG). The nonlinear stress limits of most modified binders were all found to be less than 3.2 kPa, which indicated that the stress level of 3.2 kPa included in current specifications could identify their nonlinear behavior. A higher stress level was recommended for identifying the nonlinearity of Binder 3 (PG 64-40 from Supplier A). The recovery time and the number of load cycles had significant effects on the nonrecoverable creep compliance (Jnr) and percent recovery (R) values of polymer-modified binders. Based on the testing results, it was recommended that at least 30 load cycles be included at each stress level and that the strain data from the last five cycles be used to calculate the Jnr and R values. The Jnr-diff included in current one current standard was found unwarranted to evaluate the stress sensitivity of the Alaskan polymer-modified binders used in this study.

Effect of Various Additives on the Low Temperature Performance of Petroleum Based Asphalt Binders

Transverse cracking is a prevalent problem that occurs in asphalt pavement binders in cold climates and diminishes the integrity of the road as well as shortens the life span of the road leading to premature failure. Current specification for testing petroleum asphalt binders for transverse and low temperature cracking is not elaborate enough to accurately model the engineering behaviour of the binders. Besides, neat asphalt derived from petroleum crude oil does not seem to perform well at certain low temperatures without some modification to it. Thus, a study was to be undertaken to determine the low temperature behaviour of 60-70 penetration neat binder modified with traditionally used materials such as Crushed Lime Stone Powder (CLP), Hydrated Lime (HL) and Cellulose Oil Palm Fiber (COPF) at temperatures 0 °C, -5 °C and -10 °C. The study was carried using the state of the art Bending Beam Rheometer (BBR) to assess the stiffness value, m-value and deflection level. The tests were performed in accordance with AASHTO T 313-12 specification. The results of the penetration, rotational viscosity and softening point showed that all of the modified binder specimens are within the required range. However, the performance assessments on the modified petroleum binders with additive materials showed a varied nature with CL powder being the best and the COPF the lowest. It was also observed that the crushed lime stone powder had an increase in stiffness, reduction in deflection and m-value.

Investigation of the oxidation ageing of RAP asphalt blend binders and mixtures

ABSTRACT This study evaluates the oxidation ageing properties of asphalt blends and mixtures combined with various percentages of RAP and SBS-modified binder, rejuvenator and neat binder. Four ageing methods were conducted in the laboratory on the asphalt blends and mixtures. The results showed that the G-R parameter, the ICO and the flexibility index increased, while the ΔTcr decreased with the RAP content and the ageing level. The SBS-modified binder and rejuvenator improved the cracking resistance of the RAP binder and mixture. After PAV 20 h ageing, the asphalt blends containing a low amount of RAP were equivalent to their virgin binder after PAV 40 h ageing. The asphalt blends containing a low amount of RAP after PAV 40 h ageing were equivalent to their virgin binder after PAV 60 h ageing. It was found that binders subjected to RTFO, PAV 20 h ageing, PAV 40 h ageing, and PAV 60 h ageing had rheological and chemical properties equivalent to those of loose mixtures subjected to the STOA protocol for 4 h at 135°C, the LTOA protocol for 8 h at 135°C, the LTOA protocol for 12 h at 135°C, and the LTOA protocol for 24 h at 135°C, respectively.

Chemical, thermophysical, rheological, and microscopic characterisation of rubber modified asphalt binder exposed to UV radiation

In this work, the effect of ultraviolet (UV) radiation on samples of asphalt binder mixed with crumb rubber is studied. Two sets of samples are characterised using a PG 64-22 neat binder with different percentages of rubber particles being 0, 16.6, and 20.0 wt.%. One set of the samples was stored at ambient temperature (called the unaged set) and the other was inserted inside an accelerated weathering tester for 100 h (called the UV-aged set). Thermal conductivity, chemical indices, rheology, and morphology of both sets of samples are tested using the flash method, differential scanning calorimeter (DSC), Fourier-Transform Infrared Spectroscopy (FTIR), dynamic shear rheometer (DSR), and Scanning Electron Microscope (SEM), respectively. Results show that the addition of rubber leads to a reduction of specific heat for the rubber-modified binders. Specific heat capacities of the three UV aged samples are larger than those of their unaged counterparts, and the 16.6%-aged has the highest value. FTIR spectra of the three unaged samples are very similar, whereas distinct changes occur after UV exposure. The normalised absorbance of the peak associated with S = O group increases and the peak for the aliphatic group decreases after UV aging, showing some evidence of oxidation due to UV aging. Use of crumb rubber in the binder decreases the thermal conductivity and 20.0 wt.% sample is even less conductive compared to the 16.6 wt.%. At all temperatures above 25°C, aged samples have lower thermal conductivity than the unaged ones, except neat binder which is opposite. Rheological measurements show that the complex modulus of the samples increases with the addition of rubber particles and also after aging. However, 16.6% rubber-modified sample shows the least increase in modulus after aging. Microscopic morphology shows that UV radiation causes cracks in both neat and rubber modified binder. Smaller cracks are seen to form, and the cracked pieces are stuck together in the rubber modified binders, whereas less cohesion between the cracks is observed in the neat binder.

Assessment of Various Approaches to Determining Binder Bending Beam Rheometer Low Temperature Specification Parameters from Dynamic Shear Rheometer Test

The current asphalt binder performance grading system employs Dynamic Shear Rheometer (DSR) testing to determine high and intermediate temperature rheological properties. In recent years, the ability to measure DSR instrument compliance has allowed researchers to reliably measure low temperature binder properties as well. Low temperature characterization using DSR requires substantially smaller amount of binder as compared to the currently employed binder testing method, Bending Beam Rheometer (BBR). For these reasons and the possibility of using one piece of equipment for full characterization of asphalt binders, previous research has investigated DSR as an alternative to replace BBR testing by determining equivalent creep stiffness (S) and slope (m-value) from shear complex modulus. Different methods have been proposed to determine BBR specification parameters from DSR data and their viability has been evaluated primarily for virgin binders. The objective of this paper is to further assess the applicability of different methods to determine S and m-values from DSR data for four neat binders as well as extracted and recovered binders from eighteen different mixture samples. The variables within the mixtures include lab versus plant production, aggregate size and gradation, binder PG and source, and recycled material type and content. The methods employ different interconversion methods, ranging from exact interconversions to regression-based estimates. The shear relaxation modulus or creep stiffness and slope are correlated to S and m-value measured from BBR testing. The study also investigates the impact and differences due to use different interconversion methods. The results show that the Christensen approximate interconversion is adequately able to predict parameters from DSR results that are equivalent to S and m-value determined from BBR testing. The exact interconverted shear creep stiffness and shear relaxation modulus using generalized Maxwell model are compared to lab measured S and m values, results show that a linear relationship exists between these parameters. Finally, a simple equation is developed to enable estimation of BBR S and m-value from a single point measurement of complex shear modulus and phase angle. This contribution is expected to have a practical use by providing a platform to estimate low temperature specification parameters from a single point DSR measurement.

Rheology and mix performance of rejuvenated high RAP field produced hot mix asphalt with a soybean derived rejuvenator

A laboratory study was conducted to determine the optimum dosage of a bio-based rejuvenator, epoxidised methyl soyate (EMS), needed to obtain a mix design containing 30% unfractionated recycled asphalt pavement (RAP) using a neat asphalt binder with performance grade (PG) 58-28S, rated for standard traffic to meet performance criteria for a PG 58-28S. Based on running a comprehensive rheological characterisation using Superpave binder criteria, 3% EMS by weight of the neat binder was needed to obtain a PG 58-28S at proportions of (75.5% neat binder w/ 3% EMS, and 24.5% RAP extracted binder). The 3% EMS is equivalent to 0.126% by weight of the total mix. Through lab verification, the mix design with 0.126% EMS was shown to meet performance criteria for moisture susceptibility/rutting and low temperature cracking. Field produced mix with 0.126% EMS by weight of total mix was also shown to pass the performance criteria as well for the aforementioned properties. However, the field produced control mix with 20% RAP was not shown to pass criteria for low temperature at −18°C, and thus the field produced control mix became rated as a PG 64-22S. In addition, field density was checked for both the control mix and EMS RAP mix, where both sections had pay bonuses of 3.1% and 4%, respectively.

Effect of activated carbon obtained from vinasse and marc on the rheological and mechanical characteristics of the bitumen binders and hot mix asphalts

This study examined the effect of the activated carbon, obtained from marc and vinasse agricultural wastes and used in the bitumen modification, on the rheological characteristics of bitumen binders and mechanical properties of hot mix asphalt. For this purpose, the activated carbon, obtained from vinasse generated at distillation step in the alcohol production from molasses together with grape marc, was used. The activated carbon was added to neat bitumen (PG 58–16) in 3 different ratios (5%, 10%, and 15% by weight of neat binder). The following tests were applied to the neat and modified bitumen: BBR (bending beam rheometer), DSR (dynamic shear rheometer), rotational viscosity, softening point, and penetration. The HMA samples were prepared using the neat and modified binders. The following tests were applied to the HMA samples: Marshall stability and flow, resistance against the damage induced by moisture, indirect tensile stiffness modulus, cyclic creep, and indirect tensile fatigue. Considering the binder test results, it was determined that using the activated carbon in the bituminous modification increased the stiffness and high-temperature performance of the bituminous binders, while the low-temperature performance was not affected much. Based on the mixture tests, it was found that using the activated carbon modified bitumen increased the Marshall stability, stiffness, resistance against the fatigue cracking, and permanent deformation of mixes. On the other hand, the use of activated carbon in bitumen modification adversely affected the resistance against the moisture-induced damage.

Utilização do ensaio de flexão sobre amostra semicircular para avaliação da propagação do trincamento em misturas com diferentes ligantes

Neste trabalho é estudada a propagação de fissuras e ruptura em misturas asfálticas através do ensaio de flexão semicircular. Trincamentos que surgem nos revestimentos asfálticos revelam-se como um dos principais danos que afetam diretamente a serventia e qualidade dos pavimentos flexíveis. Esta pesquisa busca contribuir para a análise da resistência ao trincamento, bem como propagação do trincamento até a ruptura de misturas asfálticas onde são utilizados três diferentes tipos de ligantes. Para este fim empregou-se o ensaio de flexão em amostra semicircular com fenda, estático (EEFAS) e dinâmico (EDFAS). Foram analisadas três composições, dosadas pelo método Superpave: uma com cimento asfáltico de petróleo (CAP), outra com asfalto modificado por polímero (AMP) e a terceira com asfalto borracha (AB), denominadas, respectivamente, como misturas A, B e C. Os resultados indicaram maior rigidez da mistura com AMP, que também apresentou maior vida de fadiga. Por outro lado, as amostras com CAP e AB apresentaram-se dúcteis e com menor velocidade de propagação das microtrincas.

A Novel Method for Polymer Content Determination in Asphalt Binder and Emulsion

Modification of asphalt binder is a must to enhance the performance of asphalt binder. The objectives of this study are to develop an extensional deformation test method using a Sentmanat Extensional Rheometer (SER) fixture inside a Dynamic Shear Rheometer (DSR) and to investigate the relationship between different percentages of latex polymer and force ductility in polymer (latex) modified asphalt emulsion (PMAE) and polymer modified asphalt binder (PMAB). The sample geometry used in this study is 3 mm × 0.72 mm. Total twenty-four samples are tested by the SER where twelve samples are PMAE and twelve samples are PMAB. One neat binder PG 64-22 and one PMAE are used. 2%, 4% and 6% latex are mixed with PG 64-22 by a mechanical mixer and a high shear mixer for making PMAB. PMAEs are collected from the manufacture with 0%, 2.5%, 4% and 5.5% latex in it. Second peak elongation force, F2 is only obtained from the latex modified binders and emulsions. First peak elongation force, F1 has no linear correlation in case of PMAE and PMAB where F2 has a linear correlation with the percent of the polymer in the PMAE and PMAB with R2 values equal to 0.9934 and 0.9535 respectively indicating extensional deformation test with SER is very promising. Additionally, DSR temperature sweep test results and multiple stress creep recovery (MSCR) test results indicate that F2 is a better indicator of polymer content than rutting factor G*/sinδ and non-recoverable creep compliance, Jnr.

Fatigue resistance of asphalt binders and the correlation with asphalt mixture behaviour

The prediction of asphalt pavements performance in relation to the main distresses has been proposed by different researchers, by means of laboratory characterisation and field evaluation. With respect to fatigue, there are different approaches to determine what failure criterion to be considered, what testing conditions to be used and which specimens’ geometry to be produced. Tests performed in asphalt binders and mixtures have been recommended to characterise the fatigue resistance, and correlations among the several scales are proposed in order to make it more practical and more precise to predict the performance of asphalt layers. In terms of laboratory fatigue characterisation of asphalt mixtures, some of the most common tests are the four-point bending beam, diametral compression, the push-pull tests, among others. The characterisation of asphalt binders is also relevant, since fatigue is dependent on their rheological characteristics. Linear viscoelastic parameters of the binders, time sweep and amplitude sweep tests were used to rank three asphalt binders (one neat 30/45 penetration grade binder; one SBS-modified binder; and one highly modified asphalt, HiMA) in terms of fatigue behaviour. HiMA showed the highest fatigue resistance. One dense hot mix asphalt (HMA) mixture (prepared with the AC 30/45 neat binder) was characterised in terms of different fatigue test methods and correlated with binder tests, comparing the two scales approaches. The fatigue life of the asphalt mixture followed in agreement with results from the asphalt binder.

Characterizing the Temperature Effects on Rutting and Fatigue Properties of Asphalt Binders Based on Time-Temperature Superposition Principle

Abstract The objective of this article is to investigate the effects of temperature on rutting and fatigue cracking resistance of asphalt binders based on the time-temperature superposition principle (TTSP). In this study, the TTSP approach was employed to interpret the results of multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS) tests for both neat and styrene-butadiene-styrene (SBS)–modified asphalt binders. The higher stress level of 3.2 kPa in the standard MSCR test procedure was extended to 10 and 15 kPa to verify the stress sensitivity of the nonrecoverable compliance (Jnr). A loading duration of 5 minutes in the standard LAS test was extended to 10 and 15 minutes to develop the fatigue failure criterion at different conditions. The results demonstrate that the time-strain curves of the neat binder during the MSCR tests under different temperatures can be unified into a single strain master curve using the TTSP shift factors, based on which the predictive Jnr showed good agreement with the measured values. This TTSP-based analysis approach does not work well for the MSCR results of the SBS-modified binder at high temperatures. However, the fatigue failure criterion determined from the LAS tests under different temperatures was verified to be successfully constructed into a single failure criterion according to the TTSP approach for both the neat and SBS-modified binders. Therefore, only an additional caution is raised for the TTS-based analysis on rutting resistance of the modified binder in a high temperature range.

Sustainability Assessment of Green Asphalt Mixtures: A Review

During recent decade, the pavement sustainability has received much attention by road agencies, companies, governments and research institutes. The aim of this paper is to introduce and evaluate the sustainability of the technologies developed or underdeveloped to address environmental issues of asphalt mixtures, and the waste materials and by-products that can be recycled and reused in asphalt production. Warm Mix Asphalt (WMA) technology, the most popular waste materials to substitute neat binder (crumb rubber modifier (CRM), recycled plastic (RP), vacuum tower bottoms (VTB)) and/or virgin aggregates (reclaimed asphalt pavement (RAP), reclaimed asphalt shingles (RAs), construction and demolition (C and D) wastes, steel and copper slags), and bio-binders were evaluated with respect to their environmental and economic benefits and engineering performance as the main components of pavement sustainability. The performance evaluation was carried out by examining rutting, moisture susceptibility, thermal and fatigue cracking resistance. Two main environmental impacts, greenhouse gas (GHG) emission, and energy consumption were considered to study the environmental effects of these technologies and materials. Additionally, the economic effect was investigated considering initial cost and long-term benefit. Results of investigation illustrated that although each individual technology and waste material is valuable in terms of performance and/or the environment, specific combinations such as WMA + RAP, WMA + CRM, RAP + CRM, and WMA + CRM + RAP lead to further benefits. Notably, these combinations suffer from a lack of comprehensive economic analysis, thus, their sustainability cannot be fully assessed and is prone to future studies.

Bone Glue Modified Fuel Resistant Asphalt Binder

Abstract Fuel resistant asphalt (FRA) is the binder that can delay hydrocarbon fuel damage by resisting the cut-back properties of hydrocarbon fuels such as gasoline, kerosene, etc. The high solubility of asphalt binder in hydrocarbon fuels results in pavement damage that is due to fuel/oil spills at airports, parking lots, drive ways, and roads. FRA can effectively be used to minimize the damage caused by hydrocarbon fuels and improve overall performance of the pavement structure. The additives/composition used in the past to develop FRA were not fully disclosed by the inventors. This research study focused on developing FRA for commercial use using a biopolymer as an additive. Fuel resistance testing, along with mechanical performance testing, was used to evaluate the fuel resistance capabilities and performance of modified binder. Furthermore, a conventional styrene butadiene styrene modified binder was used to compare the fuel damage resistance capabilities and performance characteristics of bio versus synthetic polymer-modified binders. The biopolymer not only significantly enhanced the fuel damage resistance of the neat binder but also improved mechanical properties of the neat binder. Biopolymer-modified asphalt binder showed improvement in rut resistance, elastic response, and performance grade at intermediate and high temperatures.

Short- and long-term rheological and chemical characteristics of nanomodified asphalt binder

Due to the special characteristics of nanoparticles, pavement engineers have used nanoparticles as an additive in asphalt pavement to improve pavement performance. This study focuses on characterizing modified asphalt performance using nanoclay particles compared to the unmodified asphalt binder. For this evaluation, 3% of nanoclay particles were added to a neat binder to prepare the nanomodified binder. Then, the modified and unmodified binders underwent a short- and long-term aging process using the Rolling Thin Film Oven (RTFO) and two cycles of Pressure Aging Vessel (PAV). Finally, the Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), and Fourier-Transform Infrared Spectroscopy - Attenuated Total Reflection (FTIR-ATR) tests were carried out in each aging step to assess and monitor the rutting, fatigue, low-temperature performance, durability, and chemical changes of binders during the aging process. The results of this study proved the enhanced properties and performances of the nanomodified binder compared to the unmodified binder. These results can pave the path with the use of nanomodified binders in the recycling of aged pavement and construction of roads that experience poor weather conditions and high traffic loads.

Optimization of mixing time for polymer modified asphalt

Asphalt pavement made with neat binder is not sufficient to resist heavy traffic loads as well as harsh environmental condition. Therefore, there is a need to modify the binder with polymers in order to improve its properties. From literature, it was indicated that various blending process parameters, namely, blade shape, temperature, shear rate and mixing time influenced the properties of the produced polymer modified asphalt. In this study, the influence of mixing time on six different types of polymer with 60/70 asphalt binder was focused. The polymers were blended with asphalt binder and inspected at 30 minutes intervals during the mixing process. Then, all the samples were tested through Dynamic Shear Rheometer at 58°C, 64°C and 70°C. It was shown that the complex modulus (G*) values at these temperature levels for all polymers modified asphalt indicated proper particles dispersion within the binder. The optimal blending time, which produces the best rheological properties of all modified asphalt is 30 minutes except for asphalt modified with Lucolast7010 and Anglomak2144, which is 60 minutes. In conclusion, mixing time has significant influence on the particle distribution of polymer within the binder to ensure the quality of asphalt-polymer blend.

Laboratory Comparison of Permanent Deformation and Fatigue Behavior of Neat, Polymer, and Rubber-Asphalt Binders

Fatigue cracking and rutting are among the major types of distresses to be considered in flexible pavement design. In this context, the choice of the asphalt binder plays a major role in both the fatigue behavior and permanent deformation resistance of the asphalt mixture. This study was conducted to assess the permanent deformation and fatigue behavior of a field-blended rubber-asphalt (CRMA) and compare the results with typical binders used in Brazil. The neat binder used for modification was also employed as a control and as a base for polymer modification (SBSA). The binders were evaluated using the multiple stress creep and recovery (MSCR) for permanent deformation behavior, and the time sweep (TST) and linear amplitude sweep (LAS) tests for fatigue behavior. Modification of the neat binder resulted in an increase in percentage recovery in the MSCR, whereas the percentage recovery for CRMA was the highest among the three binders at any given temperature. The non-recoverable creep compliance for the CRMA was lower than that exhibited by the neat and SBSA binders for both stress levels for the range of temperatures tested. Binder modification resulted in an improved fatigue behavior compared with the neat binder according to the TST and LAS, whereas rubber modification resulted in the best fatigue behavior. Fatigue life prediction by TST was consistently higher than fatigue life prediction in the LAS test, probably because different criteria were used for determining failure in each test (ranking of the binders remained constant regardless of the criteria used).

Aggregate–binder adhesiveness assessment and investigation of the influence of morphological and physico-chemical properties of mineral aggregates

Aggregate–binder adhesiveness in asphalt mixtures is affected by the physico-chemical properties of aggregates and asphalt binder. The objective of this paper is to analyse how aggregate morphological and physico-chemical properties affect the aggregate–binder adhesiveness measured by different techniques. Two aggregate sources (granitic and phonolitic) combined with two asphalt binders (a neat binder and the same binder modified by an anti-stripping agent) were used. Grounded plastic bags were also used as an additive to improve aggregate–binder interface properties. The adhesiveness test used follows ABNT 12583 (similar to static water storage according to EN 12697-11B) and subsequent digital image processing (DIP), developed in a previous work. Absorption was measured by a classical immersion weighting procedure (DNER 081), while angularity and texture were determined using the Aggregate Image Measurement System (AIMS). Aggregate’s chemical composition was investigated by X-Ray Fluorescence. Moisture-induced damage resistance was determined by the modified Lottman test (ABNT 15617). Asphalt Bond Strength (ABS) tests were performed with different water conditioning times. DIP allowed correlating adhesiveness to different parameters, such as angularity, texture, porosity and oxide content of the aggregate, and also to moisture-induced damage test results and the ABS test results. Results show that the granitic aggregate presented better adhesiveness with both the neat binder and the binder with anti-stripping agent. The mixture with grounded plastic bags also had better adhesiveness when compared to the control mixture. Aggregate’s angularity, texture and porosity do not appear to affect aggregate–binder adhesiveness, whereas Fe2O3 and CaO content presented excellent correlations with the adhesiveness test analysed by DIP. The asphalt film dislocation test analysed by DIP also presented strong correlation with the moisture-induced damage test. It seems possible to establish a reliable limit for DIP results in this simple test to prevent mixtures of being susceptible to moisture damage.