Superpave

The impact of temperature on the mechanical properties and thermal susceptibility of the railway bituminous sub-ballast
layer, has served as motivation to develop the advanced measurement of thermal cycles in this layer and, an evaluation of the average
seasonal temperatures interpolated by sinusoidal functions, of which characteristic parameters are determined. According to weather
situation, Barber’s temperature model was used to prove the effectiveness for the railway superstructure. It is included the assessment
of improved modified asphalt mixes performed with coarse rubber from scrap tires, having 1.5 to 3 percent of crumb rubber (particle
size 0.2-4 mm) by weight of the total mix, as sub-ballast layer in railway and base layers on roads, recurring to the Superpave mix
design compaction enhanced after computer simulations to evaluate real stresses derived from the rail traffic and climatic conditions.
This article following the assessment of the average seasonal temperatures, involves the characterization of rubberized materials with
attention to crumb rubber properties, designed with dry technology, to enhance the bitumen-rubber and binder-voids ratios. Indirect
tensile strength and water sensitivity tests were applied for the evaluation of its mechanical properties including dynamic complex
modulus at elevated temperature to measure the amount of bitumen absorbed by the rubber. The rubberized mix-results obtained and
the comparison with a conventional HMA (hot mix asphalt) show that these dry rubber bituminous mixtures are particularly effective in
damping vibrations. The purpose of using rubber modifiers in hot mix asphalt to obtain a stiffer-elastic sustainable material has been
achieved for the assessment of its behavior in sub-ballast/base layers.

— The application of bituminous mixtures modified with rubber from scrap-tires require attention and care during mixing and compaction. Rubber modifies the properties because it reacts in the internal structure of bitumen at high temperatures changing the performance of the mixture (interaction process of solvents with binder-rubber aggregate). The main change is the increasing of the viscosity and elasticity of the binder due to the larger sizes of the rubber particles by dry process but, this positive effect is counteracted by short mixing times, compared to wet technology, and due to the transport processes, curing time and post-compaction of the mixtures. Therefore, negative effects as swelling of rubber particles, rebounding effect of the specimens and thermal changes by different expansion of the structure inside the mixtures, can change the mechanical properties of the rubberized blends. Based on the dry technology, different asphalt-rubber binders using devulcanized or natural rubber (truck and bus tread rubber), have been used to show how these defects occur and, at the same time, to solve the problems generated in dense-gap graded rubber modified asphalt concrete mixes (RUMAC) to enhance the stability, workability and durability of the compacted samples by Superpave gyratory compactor method. This paper specifies the procedures developed in the Department of Civil Engineering of the University of Palermo during September 2016 to March 2017, for characterizing the post-compaction and mix-stability of the one conventional mixture (hot mix asphalt without rubber) and two gap-graded rubberized asphalt mixtures, adopting the granulometric characteristic grading curve for rail sub-ballast layer, with nominal size of Ø22.4 mm of aggregates according European standard. Thus, the main purpose of this laboratory research is the application of ambient ground rubber from scrap tires processed at conventional temperature (20 ºC) inside hot bituminous mixtures (160-220 ºC) as a substitute for 1.5%, 2% and 3% by weight of the total aggregates (3.2%, 4.2% and, 6.2% respectively by volumetric part of the limestone aggregates of bulk density equal to 2.81 g/cm 3) considered, not as a part of the asphalt binder. The reference bituminous mixture was designed with 4% of binder and ±3% of air voids, manufactured for a conventional bitumen B50/70 at 160 ºC-145 ºC mix-compaction temperatures to guarantee the workability of the mixes. The proportions of rubber proposed are #60-40% for mixtures with 1.5 to 2% of rubber and, #20-80% for mixture with 3% of rubber (as example, a 60% of Ø0.4-2 mm and 40% of Ø2-4 mm). The temperature of the asphalt cement is between 160 and 180 ºC for mixing and 145 and 160 ºC for compaction, according the optimal values for viscosity using Brookfield viscometer and " ring and ball "-penetration tests. These crumb rubber particles act as a rubber-aggregate into the mixture, varying sizes between 0.4 mm and 2 mm). in a first fraction, and 2 and 4 mm as second proportion. Ambient ground rubber with a specific gravity of 1.154 g/cm 3 is used. The rubber is free of loose fabric, wire and other contaminants. It was found optimal results in real beams and cylindrical specimens with each HMA mixture reducing the swelling effect. Different factors as temperature, particle sizes of rubber, number of cycles and pressures of compaction that affect the interaction process are explained.

The objectives of this study are focused on the ideal methodology and the dimensioning of the railway superstructure , involving the use of a bituminous sub-ballast layer modified with recycled natural rubber tire out-of-use. The previous study of the thermal transmission in each Railtrack layer, the analysis of the traffic in high-speed lines and the revision of the thermal-mechanical models have motivated this research. An experimental methodology has been optimized for the application of the volumetric mix-design with the gyratory compactor (SGC). According to the meteorological situation and applying experimental models based on thermal conductivity interpolated by sinusoidal functions, a laboratory study of conventional bituminous mixtures and improved mixtures of asphalt modified with coarse rubber waste tires is illustrated. The enhanced methodology entails a case study where compacted mixes are used by SGC, replacing rubber between 1.5 and 3 percent of rubber (particle size 0.2-4 mm) in the total weight of the blend. After the evaluation of the average seasonal temperatures, the mixtures were designed considering the dry process, as an advanced measure of sustainability and for their demonstrated improvements in thermal behavior and resistance to fatigue. A step-by-step manufacturing process is provided to avoid swelling problems in the post-compaction phase characteristic of dry mixes. The purpose of using rubber modifiers in the hot mix asphalt has been achieved to obtain an elastic sustainable material for the evaluation of its behavior in sub-ballast layers.
CITE AN ARTICLE
Soto, F. M., & Di Mino, G. (2018). “Improvements in the mix-design, performance features and rational methodology of rubber modified binders for the thermal evaluation of the railway sub-ballast”, (IJRSM/F09/17) International Journal of Research Science and Management, ISSN: 2349-5197, Volume 5, Issue 2, February 2018].

The impact of temperature on the mechanical properties and thermal susceptibility of the railway bituminous sub-ballast layer, has served as motivation to develop the advanced measurement of thermal cycles in this layer and, an evaluation of the average seasonal temperatures interpolated by sinusoidal functions, of which characteristic parameters are determined. According to weather situation, Barber's temperature model was used to prove the effectiveness for the railway superstructure. It is included the assessment of improved modified asphalt mixes performed with coarse rubber from scrap tires, having 1.5 to 3 percent of crumb rubber (particle size 0.2-4 mm) by weight of the total mix, as sub-ballast layer in railway and base layers on roads, recurring to the Superpave mix design compaction enhanced after computer simulations to evaluate real stresses derived from the rail traffic and climatic conditions. This article following the assessment of the average seasonal temperatures, involves the characterization of rubberized materials with attention to crumb rubber properties, designed with dry technology, to enhance the bitumen-rubber and binder-voids ratios. Indirect tensile strength and water sensitivity tests were applied for the evaluation of its mechanical properties including dynamic complex modulus at elevated temperature to measure the amount of bitumen absorbed by the rubber. The rubberized mix-results obtained and the comparison with a conventional HMA (hot mix asphalt) show that these dry rubber bituminous mixtures are particularly effective in damping vibrations. The purpose of using rubber modifiers in hot mix asphalt to obtain a stiffer-elastic sustainable material has been achieved for the assessment of its behavior in sub-ballast/base layers. Highlights  An innovative approach for the volumetric design of bituminous mixture with rubber (dry process);  Optimal parameters of temperature and traffic to characterize the mixture for a sub-ballast layer;  Applicability of Barber forecasting model used in the field road, to the railway superstructure;  Performance of the design process for the volumetric analysis of rubberized asphalt;  160 kN and 80 kN, respectively, rail equivalent axle load (R ESAL) were selected comparing sub-ballast vs. road base course solicitations induced for each layer;  Increase of workability and compaction properties decreasing air voids content to 3%-4% of the total mix weight;  Crumb rubber percentage between 1.5% to 2% and a digestion time of 120 min produced the optimal results.

Bituminous sub-ballast is an alternative solution to the unbound granular sub-ballast used in the railway track due to several
benefits that it can provide. Indeed, it contributes to maintain the moisture content in the subgrade unchanged during all year. This
decreases the subgrade deterioration process. Moreover, the presence of bituminous sub-ballast can also reduce vertical stiffness
variations on the track; it can have a positive effect in the maintenance needs at transition sections (bridge-embankment) and in the
attenuation of the vibrations induced by the rail traffic. Despite the importance of the presence of the bituminous sub-ballast to conceive
the construction and/or rehabilitation of sustainable infrastructure, in literature, there are only fragmentary information regarding the
definition of benchmark criteria for their mix design. The superpave mix design approach used in road domain is applied systematically
in the railway domain, without being adjusted for different load configuration of the rail track system. This research work aims at
defining the benchmark criteria for the bituminous sub-ballast mix design to reduce the approximations involved in the recipe
optimization due to the limitation of applying the superpave system in the railway domain. The methodology proposed aims at selecting
the RESAL (rail equivalent single axle load) and therefore, transforming the entire traffic spectrum on the track lines in number of
ESALs. Afterwards, the Ndesign has been calculated as function of the rail traffic level. Finally, a case study of bituminous sub-ballast
mix design has been investigated for a first verification of the methodology proposed.

The paper describes the results obtained in our laboratory as part of an international project under the Organization for Economic Co-operation and Development (OECD) Road Transport Research program. The main objective is to determine whether a surface pavement with radically extended and maintenance-free service life is economically viable on high trafficked highways, when costs of road user delays due to road maintenance and rehabilitation are considered.

Toward this objective, the characteristics of an epoxy asphalt binder are compared with those of a number of polymer-modified binders using the SuperpaveTM binder protocols. In addition, asphalt mixes were prepared with each binder type utilizing similar aggregates and mix designs. Tests conducted with the Superpave Shear Tester (SST), Hamburg Wheel Tracking Device (WTD), Pine Wheel Tester, Thermal Stress Restrained Specimen Test (TSRST), and Simple Performance Test (SPT) indicated that the epoxy asphalt mix is a stiffer material and exhibits excellent resistance to rutting, moisture damage, and fatigue. The Superpave binder low temperature tests were considerably higher than those from the TSRST however, results from fracture testing with the Compact Tension Test and Semicircular Bending Test qualitatively suggest the epoxy asphalt to be more resistant to low temperature thermal cracking.

The paper describes the results obtained in our laboratory as part of an international project under the Organization for Economic Co-operation and Development (OECD) Road Transport Research program. The main objective is to determine whether a surface pavement with radically extended and maintenance-free service life is economically viable on high trafficked highways, when costs of road user delays due to road maintenance and rehabilitation are considered. Toward this objective, the characteristics of an epoxy asphalt binder are compared with those of a number of polymer-modified binders using the SuperpaveTM binder protocols. In addition, asphalt mixes were prepared with each binder type utilizing similar aggregates and mix designs. Tests conducted with the Superpave Shear Tester (SST), Hamburg Wheel Tracking Device (WTD), Pine Wheel Tester, Thermal Stress Restrained Specimen Test (TSRST), and Simple Performance Test (SPT) indicated that the epoxy asphalt mix is a stiffer material...

... Number of load cycles to fatigue failure AASHTO TP 8-94 (2002) method Quantitative failure criterion [present work] Qualitative failure criterion Al-Khateeb and Shenoy (2004) ... SBS RG 12,372 13,144 10,000 EVA 5,905 12,654 36,700 EVA G 7,183 11,840 16,700 ...

Asphalt is a visco-elastic material having properties of elastic solid at low temperature and viscous liquid at high temperature. Properties of asphalt binder depend upon temperature, rate of loading and aging conditions. Although asphalt binder is only 4-5 % of asphalt concrete mix by weight but it plays a vital role in defining the pavement performance. That is, pavement response is heavily dependent upon the viscous and elastic properties of asphalt. In this research six asphalt samples were obtained from Attock and Karachi oil refinery and Dynamic Shear Rheometer was used in the laboratory to evaluate their viscous and elastic properties. Witczak predictive model was used to predict the binder viscosity and phase angle by using complex shear modulus and viscosity temperature susceptibility. The study revealed that Karachi virgin asphalt grades are more elastic as compared to Attock virgin asphalt grades both at low and high temperature. Similarly Attock PMB is more stiff and elastic as compared to Karachi 40/50, 60/70, and Attock 60/70. The research also revealed that Attock PMB has lesser temperature susceptibility as compared to virgin grades which makes it more suitable to resist rutting and cracking in extreme climatic conditions of Pakistan.

The paper aims to identify those characteristics of bitumen which have the greatest impact on asphalt mixture low-temperature performance. It was observed that stiffness and m-value of bitumen from BBR test were moderately related to stiffness and m-value of asphalt mixture obtained from 3 PB test. Simultaneously those rheological properties significantly impact on cryogenic stresses induced during TSRST test. The multiple regression model was developed and it implied that mixture failure temperature depends both on rheological properties, brittle fracture and content of bitumen, what means that only comprehensive assessment of bitumen properties enables reasonable assessment of its low-temperature performance.

The present work provides a standardized method by which various mixtures can be compared and their expected performance can be assessed in a uniform manner using the Superpave shear tester. Based on the present findings, it is evident that complete mixture evaluation can be done through the frequency sweep at constant height (FSCH) data from the Superpave shear tester (SST), without the need to generate the repeated shear at constant height (RSCH) data. This would reduce the experimental time without compromising the information obtained.
FSCH and RSCH data at different temperatures are generated on the SST for a number of aggregate-asphalt mixture combinations. The shear moduli versus frequency data from the FSCH at different temperatures are unified to form a single curve for each mixture so that a specification parameter TS (°C) can be determined.
Each unified curve is fitted with a constitutive equation from which model parameters are evaluated. The slope B1 in the low frequency region of the unified curve, when normalized with the term (T/ TS), results in a parameter that relates to the permanent strain after 5000 cycles in RSCH at any temperature T. There is a good possibility that the slope B2 in the high frequency region of the unified curve may relate to distresses in the intermediate temperature range, such as, fatigue. If this is proven true through future research, then the Superpave shear tester could earn the distinction of being a ‘Simple Performance Tester’

The data generated from the Superpave shear tester (SST) frequency sweep at constant height (FSCH) test is available in terms of the complex shear modulus G* versus frequency at the temperature of measurement. An attempt is made to unify the sets of curves generated at different temperatures on various mixtures. The procedure involved the use of a normalizing frequency parameter. The temperature at which the normalizing parameter becomes equal to one is suggested as a specification parameter for assessing mixture performance. This specification parameter was determined for various mixtures of known performance and found to follow performance ranking in all the studied cases.

The paper describes the results obtained in our laboratory as part of an international project under the Organization for Economic Co-operation and Development (OECD) Road Transport Research program. The main objective is to determine whether a surface pavement with radically extended and maintenance-free service life is economically viable on high trafficked highways, when costs of road user delays due to road maintenance and rehabilitation are considered. Toward this objective, the characteristics of an epoxy asphalt binder are compared with those of a number of polymer-modified binders using the SuperpaveTM binder protocols. In addition, asphalt mixes were prepared with each binder type utilizing similar aggregates and mix designs. Tests conducted with the Superpave Shear Tester (SST), Hamburg Wheel Tracking Device (WTD), Pine Wheel Tester, Thermal Stress Restrained Specimen Test (TSRST), and Simple Performance Test (SPT) indicated that the epoxy asphalt mix is a stiffer material...

Literature revealed the potential of using guayule resin for asphalt cement replacement from the binder’s perspective. However, monitoring guayule resin through binder-aggregate mixture could disclose its performance through field. In this study, designated binders were employed to investigate the applicability of such an innovative replacer through mixture, which were neat asphalt and guayule-based binders (neat guayule, asphalt-rubber-guayule, guayule-rubber binders). Consecutively, field-simulated lab mixtures were prepared to investigate the major distresses. Moisture damage, rutting, fatigue cracking, and thermal cracking resistances were investigated using the modified Lottman (TSR) test, rut test by asphalt pavement analyzer (APA), semi-circular bending (SCB) test, and disk-shaped compact tension (DCT) test, respectively. Additionally, the Hamburg wheel-tracking (HWT) test was employed to evaluate moisture susceptibility and rutting resistance. Outcomes revealed that the neat...

The impact of temperature on the mechanical properties and thermal susceptibility of the railway bituminous sub-ballast layer, has served as motivation to develop the advanced measurement of thermal cycles in this layer and, an evaluation of the average seasonal temperatures interpolated by sinusoidal functions, of which characteristic parameters are determined. According to weather situation, Barber's temperature model was used to prove the effectiveness for the railway superstructure. It is included the assessment of improved modified asphalt mixes performed with coarse rubber from scrap tires, having 1.5 to 3 percent of crumb rubber (particle size 0.2-4 mm) by weight of the total mix, as sub-ballast layer in railway and base layers on roads, recurring to the Superpave mix design compaction enhanced after computer simulations to evaluate real stresses derived from the rail traffic and climatic conditions. This article following the assessment of the average seasonal temperatures, involves the characterization of rubberized materials with attention to crumb rubber properties, designed with dry technology, to enhance the bitumen-rubber and binder-voids ratios. Indirect tensile strength and water sensitivity tests were applied for the evaluation of its mechanical properties including dynamic complex modulus at elevated temperature to measure the amount of bitumen absorbed by the rubber. The rubberized mix-results obtained and the comparison with a conventional HMA (hot mix asphalt) show that these dry rubber bituminous mixtures are particularly effective in damping vibrations. The purpose of using rubber modifiers in hot mix asphalt to obtain a stiffer-elastic sustainable material has been achieved for the assessment of its behavior in sub-ballast/base layers.

The design of an unmodified bituminous mixture and three rubber-aggregate mixtures containing rubber-aggregate by a dry process (RUMAC) was evaluated, using an empirical-analytical approach based on experimental findings obtained in the laboratory with the volumetric mix design by gyratory compaction. A reference dense-graded bituminous sub-ballast mixture (3% of air voids and a bitumen 4% over the total weight of the mix), and three rubberized mixtures by dry process (1,5 to 3% of rubber by total weight and 5-7% of binder) were used applying the Superpave mix-design for a level 3 (high-traffic) design rail lines. The railway tracked section analyzed was a granular layer of 19cm compacted, while for the sub-ballast a thickness of 12cm has been used. To evaluate the effect of increasing the specimen density (as a percent of its theoretical maximum specific gravity), in this article, are illustrated the results obtained after different comparative analysis into the influence of varying the binder-rubber percentages under the sub-ballast layer mix-design. This work demonstrates that rubberized blends containing crumb and ground rubber in bituminous asphalt mixtures behave at least similar or better than conventional asphalt materials. By using the same methodology of volumetric compaction, the densification curves resulting from each mixture have been studied. The purpose is to obtain an optimum empirical parameter multiplier of the number of gyrations necessary to reach the same compaction energy as in conventional mixtures. It has provided some experimental parameters adopting an empirical-analytical method, evaluating the results obtained from the gyratory-compaction of bituminous mixtures with an HMA and rubber-aggregate blends. An extensive integrated research has been carried out to assess the suitability of rubber-modified hot mix asphalt mixtures as a sub-ballast layer in railway underlayment tracked. Design optimization of the mixture was conducted for each mixture and the volumetric properties analyzed. Also, an improved and complete manufacturing process, compaction and curing of these blends are provided. By adopting this increase-parameters of compaction, called " beta " factor, mixtures modified with rubber with uniform densification and workability are obtained that in the conventional mixtures. It is found that considering the usual bearing capacity requirements in rail track, the optimal rubber content is 2% (by weight).
INTERNATIONAL JOURNAL OF ENGINEERING
SCIENCES & RESEARCH TECHNOLOGY, 7(1), 483-507.
DOI: 10.5281/zenodo.1158653

Novel resources can contribute to replacing asphalt with sustainable, flexible pavement options. In this study, asphalt was replaced by guayule resin as a bioresource by-product extracted during guayule natural rubber production. Crumb rubber modifier (CRM) was used as an asphalt enhancer. According to the Superpave criteria, the designated binders were exposed to tests covering the construction process (mixing and compaction requirements), rutting, fatigue, and thermal cracking resistances through viscosity, high-, intermediate-, and low-temperature measurements, respectively. The original, short-term aging, and long-term aging conditions were simulated using tank, rolling thin film oven, and pressure aging vessel materials, respectively. Additionally, component analysis using Fourier-transform infrared spectroscopy was performed to link the rheological properties with the chemical changes. Outcomes showed a relatively lower viscosity for guayule resin than asphalt at the same high-temperature grade, thus indicating savings in plant energy consumption and environmental emissions. The CRM enhanced guayule, but not as much as asphalt, as proven by polymeric component migration through the liquid binder. This enhancement was reflected in the rheological performance in addition to other factors. The as-received guayule resin had a high oxygen content confirmed by strong absorption peak intensities of oxidative bonds (e.g., Carbonyl and sulfoxide). Such pre-oxidation was negatively reflected in the intermediate- and low-temperature performances of guayule resin and guayule-based binders. However, the investigated guayule resin compensated for asphalt replacement by 23–42% of the blend's weight.

Using the enclosed author link, it is accessible for the first 50 days (by August 16, 2021) to view and download. It will be for Elsevier subscribers thereafter.

Author Link: https://lnkd.in/grMrnuj

En Chile la selección de ligantes asfálticos se realiza por especificaciones tradicionales. Aunque aún no se implementa la especificación Superpave, se consideró importante realizar una zonificación del territorio chileno según esta metodología. Para esto se utilizó información de 94 estaciones climáticas de la Dirección Meteorológica de Chile (DMC) y de la Dirección General de Aguas (DGA), las que cuentan con información confiable para un mínimo de 20 años. Los datos meteorológicos, en conjunto con la clasificación climática de Köppen para Chile y la topografía de nuestro territorio, fueron utilizados para definir de manera aproximada las zonas donde es apropiado el uso de cada tipo de ligante asfáltico. Los resultados de la zonificación indican que la mayor parte de nuestro territorio puede cubrirse con tres tipos de ligantes asfálticos: en la zona norte y en el sur del país es recomendable utilizar un PG58-28; para la zona centro se requiere un PG64-22; finalmente para la Patagonia y alta montaña se necesita un PG52-34. Existe una pequeña zona precordillerana en la novena región donde, de acuerdo a la información climática disponible y la metodología utilizada, se requeriría un PG64-34. Las clasificaciones PG64-22, PG58-28 y PG52-34 corresponden a ligantes tradicionales y fueron zonificados para condiciones de circulación de alta velocidad y volúmenes de tránsito moderado.