Paving Grade Bitumen Research Articles

The Effect of a Liquified Wood Heavy Fraction on the Rheological Behaviour and Performance of Paving-Grade Bitumen

Biomass is one the most abundant renewable energy sources, and it can be processed through different thermochemical methods to obtain oils that can replace the petroleum bitumen used in road construction. For the construction industry to accept the bitumen replacement with bio-oil, it is necessary to know its properties and determine the applicability of conventional testing methods. This research utilized a liquified wood heavy fraction (bio-oil) obtained from waste wood through an innovative thermochemical liquefaction process. The aim was to investigate a kind of bio-bitumen produced by blending this bio-oil with paving-grade bitumen. The rheological behaviour in a wide temperature range, the performance relative to fatigue cracking and permanent deformation sensitivity, and the evolution with oxidative ageing were evaluated for the bio-bitumen and paving-grade bitumens. The bio-oil significantly affected the rheological behaviour of bitumen through an overall decrease in the phase angle and by failing the time–temperature superposition principle. The strong elastic response of the bio-bitumen improved resistance to fatigue and permanent deformation accumulation; however, resistance to oxidative ageing declined. Linear viscoelastic rheological indicators proposed in the literature to assess the material’s performance showed a similar trend of variation with oxidative ageing for bio-bitumen and paving-grade bitumen, though the indicators’ values could not be directly compared.

Evaluation of the effect of processed plastic additives on the properties of paving grade bitumen

Asfalty modyfikowane są powszechnie stosowane w budownictwie drogowym. Znane są różne metody modyfikacji, a za najlepszą i najczęściej stosowaną uznaje się modyfikację polimerem SBS. W niniejszym artykule zaprezentowano wyniki badań nad możliwością modyfikacji zwykłych lepiszczy drogowych w inny sposób, tj. przy wykorzystaniu przetworzonych tworzyw sztucznych pochodzących z recyklingu. Warunkiem wyjściowym dla tego typu modyfikacji jest zapewnienie stabilności wytworzonego materiału oraz niepogorszenie jego właściwości funkcjonalnych w porównaniu do lepiszcza bazowego. W pracy zaprezentowane zostaną wybrane wyniki badań doświadczalnych przeprowadzonych na materiałach uzyskanych ze zmieszania konwencjonalnych asfaltów drogowych 50/70 oraz 70/100 z dodatkami wytworzonymi z PP, PS, LDPE, HDPE (oraz ich mieszankami). Dodatki te uzyskano w procesie pirolizy przy różnych technologiach wytwarzania z uwzględnieniem różnych wartości temperatury i czasu przetwarzania. Przeprowadzono badania podstawowe na 56 różnych kompozycjach asfaltu i dodatku w celu wyłonienia potencjalnie najlepszych wariantów do dalszej poszerzonej analizy. Zaproponowano metodę obiektywnego wyboru najlepszych mieszanin asfaltów z dodatkiem. Nie jest to klasyczna metoda rankingowa (przyznawanie punktów), a metoda bazująca na funkcji celu będącej sumą trzech funkcji składowych odpowiadających poszczególnym parametrom z odpowiednimi wagami. Metoda ta może być dość swobodnie kształtowana poprzez dobór wag albo odmienne propozycje funkcji składowych. Na tej podstawie wyłoniono dodatki, które mają najkorzystniejsze właściwości pod względem zastosowania do produkcji mieszanek mineralno-asfaltowych.

Rheological characterisation of bituminous binder blends for the design of asphalt mixes containing high recycled asphalt content

Reclaimed asphalt pavement (RAP) is gained from road reconstructions; however, its usage is less optimised in Hungary and neighbouring regions, since on the project level the proportion of RAP in the asphalt mixes is only 10-15%. This is less than the recommended level in other EU countries. The higher usage of RAP provides economic and environmental advantages, decreasing the need for new materials, the transport cost, and the carbon footprint. The composition of the resultant bituminous binder blend is a critical element in the asphalt mix design with high RA content. This paper discusses the design of the resultant bituminous binder blend to provide performance and compliance characterisation. This paper also presents the complex rheological analysis of the base bitumen, the bitumen extracted from the RA and the bituminous binder blend, applying the dynamic shear rheometer (DSR) device. It was shown that for paving grade bitumen (B), polymer modified bitumen (PmB) and rubber modified bitumen (GmB), the addition of higher proportions of RA content is possible without compromising on the performance of the binder blend. With a carefully chosen paving grade bitumen it is possible to utilise up to 40% RA content. For the polymer modified bitumen, the limit of the RA content is 20%. For the rubber modified bitumen, the various proportions of RA contents showed no or negligible changes in the characteristics of the bitumen and the RA content can reach 30% in this case.

Dynamic Viscosity Prediction of Blends of Paving Grade Bitumen with Reclaimed Bitumen

The recycling of reclaimed asphalt pavement is of significant economic and environmental benefits. In this case, however, the satisfactory performance of the final product needs scientific planning of the mixture and thorough quality control. Before its use, a number of tests must be performed to verify that the binder meets the relevant requirements and can be used in asphalt mixtures. The binder characteristics in the reclaimed asphalt pavement and the expected properties of the binder blend in the new asphalt mixture must be known. For its prediction and calculation, a European standard offers the calculation of the penetration or softening point of the binder blend in the mixture with reclaimed asphalt content. However, in some countries, the determination of paving grade bitumen types (categories) is based not on dynamic viscosity measured with DSR instrument, so other validated test and calculation methods are in force. A viscosity-based method has not yet been validated for paving grade bitumens standardized on a penetration basis, although this method is more advantageous in many aspects when monitoring daily production processes; it is much shorter and requires less material than measuring softening point or penetration. The article deals with the measurement of the dynamic viscosity of bitumen blends of asphalt mixtures made using reclaimed asphalts, determined with a dynamic shear rheometer at different frequencies (0.1–10.0 Hz sweep). Furthermore, the relationships between the different composition ratios of national paving grade bitumens classified on the bases of penetration level and bitumens from reclaimed asphalt pavement are examined.

Performance of modified bituminous binders for mastic asphalt applications: risk assessment by thermal and rheological indices

To increase the resistance to permanent deformation of mastic asphalt mixtures while maintaining workability, the use of additives has become common practice. Latter include both plastomeric polymers as well as Fisher–Tropsch (FT) waxes, giving rise to morphologically complex binders. However, field experiences indicate that such mastic asphalt mixtures are prone to failure due to cracking shortly after its use on site. Hence, the impact of such additives on the binder performance was investigated. The research approach included an analysis by both thermal as well as rheological indices, aiming for the assessment of binders’ performance and identifying possible risks related to cracking. Findings from modulated DSC and DSR measurements are presented and discussed for both a paving grade bitumen 35/50 as well as blends, following modification with plastomer and/or FT-wax at different ageing stages. M-DSC results indicated that additives studied were incompatible with the bitumen matrix, therefore negatively affecting binder performance. Moreover, the determination of rheological indices identified risks of cracking failure associated with the combined use of plastomer and FT-wax.

Evaluation of bitumen's fatigue resistance - a comparative study

Since asphalt mixtures are based on bituminous binders, a complex organic viscoelastic and time-temperature dependent material, they naturally tend to change their performance. Due to increasing traffic and axle loads, fatigue resistance is one of the most important properties of asphalt materials. The standard procedure of asphalt mixture evaluation is determining their fatigue resistance, but it is also possible to determine the fatigue resistance of bitumen on binders level. This article presents the research results of asphalt binders fatigue resistance, two paving grade bitumens and one polymer modified bitumen, in unaged and aged states. Asphalt binders were tested using three methods according to the Superpave criterion, the time-sweep fatigue test and the linear amplitude sweep test (LAS). Analysis and evaluation of the test results were carried out due to fatigue and time consumption of the testing procedure. In terms of determining the fatigue phenomenon, both in bitumen and asphalt mixture levels, the most critical aspect is the time severity of the tests and the necessity to perform such advanced testing on many test specimens. The results show that the G*·sinδ parameter should not be used to validate the fatigue life of bitumen. The result from fatigue time-sweep and LAS tests appear to give similar outcomes and correlate better, especially the LAS in higher strain levels. Furthermore, regarding test time consumption, LAS requires less time to perform and gives a more flexible approach to determining bitumen fatigue life.

Evaluation of mixture grading and binder composition effects on the characteristics of cold-recycled mixtures with foamed bitumen

The investigation was carried out to evaluate the effects of the hydraulic binder's composition on the properties of cold recycled mixtures with foamed bitumen of different gradations. The evaluated hydraulic binders were composed of Portland cement, hydrated lime and cement by-pass dusts. The ratios of these three components simultaneously varied from 20 to 60% in relation to the mass of the resultant hydraulic binder. The mixtures were composed of reclaimed asphalt from a road base (coarse or fine RAP), natural aggregates (0/2 and 0/31.5 mm) in different ratios, hydraulic binder and 70/100 foamed paving grade bitumen. It was shown that the fine and coarse mixtures responded differently to the changes in the composition of the hydraulic binder. It was found that the optimum performance of the fine and coarse graded mixtures required different binder compositions.

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

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

Reclaimed asphalt recycling agents: Looking into the blueprint of their mechanisms of action

As the global environmental crisis is reaching an irreversible point, within the roadway industry, the demand for eco-friendly products such as recycled asphalt pavement is at an all-time high. As a result, and thanks to the promising advancements made in the past decades, doubts no longer exist about the benefits of asphalt recycling. However, the current issue is how to increase the proportion of reclaimed asphalt in new road paving operations. This research study deals with one of the key factors of a successful asphalt pavement recycling; the recycling agents. Several techniques were applied to investigate the mechanism of action of two recycling agents speculated to be rejuvenators and/or flux oils using two different paving grade bitumens. In order to perform a comprehensive study, the testing scheme involved rheological, microscopic, chemical, and physicochemical analyses. Although the physical changes of the aged bitumen containing the studied recycling agents were similar, the chemical impacts were quite different as suggested by the results obtained from the tests performed in this study. The results demonstrate the rejuvenator having an edge over mere fluxing agents in the reversal of the aging phenomenon in bitumen. In fact, this could be determinant in the durability and quality of recycled asphalt pavement.

Effect of Winter Road Maintenance on the Asphalt Road Surface-Experience in Slovakia and the Czech Republic.

The properties of asphalt mixtures and the quality of their execution are key factors for their service life and durability in the pavement structure. This research aims to study the effect of deicing chemicals (sodium chloride, NaCl) on asphalt mixtures in laboratory conditions to know the changes in properties when the samples were loaded with a different number of freeze–thaw cycles. The behavior of the standardly used asphalt mixtures and bitumen binders was verified by the exposure to sodium chloride solution (20 g/L NaCl). In the first part of the experiment, penetration, elastic recovery, and softening point tests were performed for paving grade bitumen 50/70 and 70/100, and polymer-modified bitumen PMB 25/55-60. Furthermore, asphalt concrete (AC 11) mixtures with different air voids were subjected to 25, 50, and 75 freeze–thaw cycles to determine the effect on the service life of the pavement structure. Following the Czech standard, CSN 73 6161, and the TP 170 regulation for the design of asphalt pavements, the Marshall test and the stiffness modulus were determined for all asphalt samples. The obtained results show a negative effect of freeze–thaw cycles on the properties of asphalt concrete surface course mixtures and bitumen.

Effects of water-foaming and liquid warm mix additive on the properties and chemical composition of asphalt binders in terms of short term ageing process

This study investigated the effects of water-foaming of asphalt binders containing liquid warm mix additives as an intention to produce warm-mix asphalt with enhanced performance in scope of compaction and moisture resistance. Two paving grade bitumen were used as a base material – a 35/50 and 50/70 paving grade bitumen binders. The investigation involved subjecting the asphalt binders to short-term ageing using rolling thin-film oven test protocol in temperatures ranging from 123 °C to 163 °C to simulate the effects of lowered processing temperatures in warm mix asphalt techniques. The testing methods included standard classification tests, basic evaluation of foaming performance, dynamic viscosity testing, evaluation of high temperature stiffness and non-recoverable compliance using a dynamic shear rheometer as well as evaluation of changes in chemical composition of the binders using Fourier transform infrared spectroscopy. The results have shown that water-foaming of asphalt binders incorporating the liquid warm mix additive led to an additional, significant drop in their dynamic viscosity in the mixing and compaction temperature range, while no significant effects to the performance-related characteristics of the binders were observed. It was found that the small changes in asphalt binder rheology caused by water-foaming were reverted in the course of laboratory short-term ageing. The process of water foaming has induced measurable changes in the chemical structure of the investigated binders associated traditionally with oxidative ageing, however these did not affect the results after the short-term laboratory ageing using the rolling thin-film oven test protocol. Based on the conducted work it was concluded that the simultaneous use of water-foaming and the liquid warm mix additive should not have permanent effects on the performance of the investigated asphalt binders, while enabling enhanced coating and workability of the asphalt mixtures produced in lowered temperatures.

The natural bitumen additive Selenizza® SLN: A promising alternative for producing high-performance asphalt mixes

The purpose of this paper is to highlight the benefits of using natural bitumen in the context of global environmental change and increasing transportation demands in terms of traffic volume and loads. Despite the advantages of using these additives as binder modifiers to implement high modulus asphalt mixes characterized by high stiffness, high durability, superior resistance to permanent deformation, and good fatigue resistance, they remain still largely unknown and far from being effectively exploited. The paper displays for the first time a collection of scientific data based on previously published research works, enriched by new laboratory testing, whose results are not published yet. It aims to provide a comprehensive understanding of various aspects of the natural bitumen Selenizza® (extracted from the deposit located in southeast Albania) and the role that this natural additive plays in achieving the desired asphalt pavement performance. The dynamic rheological and Modulated Differential Scanning Calorimetry (MDSC) analysis proved that natural bitumens are fully compatible with straight-run bitumen and contribute to increasing the consistency, viscosity, and stability of natural bitumen-modified binders. The Rolling Thin-Film Oven Test (RTFOT), followed by Pressure Aging Vessel (PAV) aging analysis of road bitumen modified with Selenizza®, revealed that the resulting binders are resistant to aging and relatively efficient at low temperatures. A Life Cycle Assessment study compared the environmental impact of the Albanian natural bitumen production process with that of conventional crude oil bitumen, leading to the conclusion that the CO2 emission released during the production of Selenizza® is reduced by approximately 44 % compared to that of crude oil bitumen. The various research works described in this paper provide evidence that the natural bitumen-based asphalt mixes feature enhanced quality in terms of mechanical and rheological properties compared to reference asphalt mixes produced with equivalent traditional paving grade bitumen.

Effect of Mineral Fillers on Oxidative Aging of Epoxy Bitumen

AbstractThis research involving two binders, a neat 70/100 paving grade bitumen and an epoxy-diluted bitumen, evaluated the effect of hydrated lime and limestone filler on the oxidative age hardeni...

Foaming Performance and FTIR Spectrometric Analysis of Foamed Bituminous Binders Intended for Surface Courses.

This study explores the effects of foaming on three selected bituminous binders: 50/70 paving grade bitumen, 45/80-55 polymer modified bitumen and 45/80-80 HiMA binder. The first part of the investigations included the evaluation of the foaming performance in terms of foaming temperature and foaming water content with the utilization of desirability functions and based on the equality of maximum expansion ratio and bitumen foam half-life. The second part of the study investigated the effects of foaming on the chemical structure of the binders using Fourier-transform infrared spectroscopy. The results of the spectroscopic measurements permitted calculation of structural indices specific to functional groups associated with bitumen oxidation, as well as those indicative of elastomeric modification. The results have shown that the different types of bitumen exhibited different foaming characteristics, which was most evident in bitumen foam half-lives, with the HiMA binder performing the best. The spectrometric measurements did not show any significant effects of foaming on the chemical structure of the evaluated binders related to oxidative stress, neither were any major changes in the PmB-specific regions found.

Advanced Characterization of Bituminous Binders: Comparing Industrial and Paving-Grade Bituminous Binders

This paper deals with the fundamental differences between industrial and paving-grade bituminous binders. The paper is presented in two main sections: 1) a review of the materials’ colloidal structure and the required properties for the industrial and paving applications; 2) a wide range of experimental tests with which the bituminous binders were studied and compared. In this research, a 160/220 industrial bitumen was studied and compared to a paving-grade bitumen with the same penetration and with a lower penetration, 70/100 one. The research consisted of physical, chemical, thermal, microstructural, and rheological analysis to provide a comprehensive understanding of these bituminous binders of diverse applications. Overall, the comparison of the tests’ results indicated that while the asphaltene content and its characteristics have a great influence on the bitumen’s properties, it is not the only fundamental factor. During the study of the chemical structures via Atomic Force Microscopy (AFM), it was found that the Peri phase (attributed to the resins) also plays an important role, defining the bitumen’s physical visco-elastic properties. In fact, from a microstructural point of view using AFM a significant difference was notified between the industrial bitumen and the paving-grade ones. These differences allow the paving-grade bitumens to be more elastic and ductile compared to the industrial bitumen.

Research into effect of asphalt mixture aging on stiffness

The paper focuses on the research of the stiffness of asphalt mixtures exposed to short-term and long-term aging. Asphalt mixtures are exposed to this type of ageing during their production, laying and compaction and subsequently during service. The research was carried out on test samples of asphalt mixtures AC11 50/70 and AC11 PMB 45/80-75 for wearing course of asphalt pavements. The asphalt samples have been exposed to the effects of short-term and long-term ageing by the conditioning of loose mixture method. Subsequently, the stiffness modulus of asphalt mixtures at temperature 20 °C was determined by the IT-CY method according to EN 12697-26. The obtained results showed higher values of stiffness modulus for the mixture with paving grade bitumen 50/70. The largest difference in the stiffness modulus was recorded for origin asphalt mixtures. Furthermore, an increase in the mixture stiffness due to ageing was observed, more pronounced in the case of the mixture with the polymer modified bitumen PMB 45/80-75. Gradual ageing changes the properties of asphalt mixtures, which are essential for the durability of the road.

Correlation and modelling of the penetration and softening point tests of bitumen binders with a variety of physical and chemical properties

Studying bitumen has always posed a challenge to researchers owing to its extreme complexity and unique properties. To classify it commercially and to determine bitumen grade, two standard empirical tests have been adopted within the European standardized bitumen binders system [EN 12591:2009 (2009) Bitumen and bituminous binders – Specifications for paving grade bitumens]: Softening Point (SP) and Penetration (PEN). The relationship between these two tests and the physical or chemical properties of bitumen is not well understood. For the first time, this study represents an attempt to build more understanding of such a relationship through a comprehensive study of the correlation between the two standard tests and many physical and chemical properties of bitumen. A second goal is to propose some predictive models for these two tests and compare their predictive accuracy. Therefore, 13 Straight Run Vacuum Residues (SRVR) samples from different geographical origins were analyzed to measure the following parameters: Dynamic Viscosity (VisDy), Conradson Carbon Residue (CCR), C5 Asphaltenes Content (AspC5), C7 Asphaltenes Content (AspC7), Elemental Analysis (including C, H, O, N, S, Ni, and V content), Simulated Distillation (SD), Fourier-Transform Infrared Spectroscopy (FT-IR), and proton nuclear magnetic resonance spectroscopy (H-NMR). Results of studying correlations using correlation matrix and Principal Component Analysis (PCA) have emphasized the prominent effect of asphaltenes content on the other properties and the results of SP and PEN. It has also shown the potential importance of the aliphaticity/aromaticity of bitumen. Then, four models were proposed for the prediction of SP and PEN: viscosity, FT-IR, H-NMR, and multi-parameter models. Partial least squares (PLS) regression was used for building all models, except viscosity ones. All SP models, except H-NMR model, exhibited very good accuracy compared to the standard method. On the other hand, PEN was more difficult to predict than SP and only the multi-parameter model of PEN showed relatively good accuracy of prediction.

Comparative evaluation of quality of hard and special paving grade bitumen’s

The application of hard paving grade bitumen or polymer modified bitumen is one of the solutions to prevent a creep of road pavement. The implementation of special hard bitumen and multigrade bitumen starts at 80-th of the last century in a purpose to construct high module asphalt pavement. The results of comparative evaluation of conventional and fundamental (cohesion, adhesion, viscosity) quality indicators for hard paving grade bitumen and multigrade bitumen are given in the article. Low value of temperature susceptibility and a wide plasticity interval are obtained as characteristics of multigrade bitumen. The same is inherent to the air-blown bitumen, with a “gel” type structure. Low ductility and a significant change in softening point temperature after hardening can be considered as disadvantages of multigrade bitumen.

MECHANICAL AND IMAGE ANALYSIS OF ADHESION BETWEEN MINERAL AGGREGATE AND BITUMINOUS BINDER

Asphalt mixtures often fail due to poor interaction between mineral aggregate and bituminous binder. Therefore, many efforts are being made on adhesion improvement between the two materials. In this work, paving grade bitumen 50/70 was doped with two types of adhesion promoters. Asphalt mixtures composed of crushed aggregate Brant coated by binder were made and exposed to stripping water. Then, they were subjected to visual and digital image analysis aiming to quantify aggregate residual bitumen-coated areas. Besides, two cylindrical samples of aggregate were bonded together by a thin film of bitumen doped with adhesion promoters. After solidification of binder, force needed for separation of the two parts was measured. It was shown that residual bitumen-coated areas were increased by 20-30% by adding adhesion promoters into binder. Mechanical adhesion of thus modified binder to aggregate was increased by up to twice.

Investigation of the Relation between Adhesion and Water Sensitivity Test Results

Abstract The relation between the results of adhesion and water sensitivity tests was investigated. The tests were performed according to the relevant European standards. Two paving grade bitumens (PGB) with different gradations were used in combination with three adhesion additives and basic, neutral and acidic coarse aggregate. It was concluded that each of the additives enhanced the evaluation of the adhesion regardless of the type of binder and aggregate. All the additives combined with PGB 35/50 improved the water sensitivity results. A better result with PGB 50/70 was observed with only one additive. It was noted that an assessment of the efficiency of an adhesion additive based on a change in the water sensitivity value (ITSR) can contradict a change in the indirect tensile strength. The expected reduction in values with an increase in the coarse aggregate acidity was only confirmed for the adhesion test. The change in the ITSR and the indirect tensile strength of dry and wet samples did not fit the expectations. The correlation between the results of the adhesion and water sensitivity test was low and could not be recommended for predicting the indirect tensile strength of asphalt from rolling bottle test results.