Ensayo Dinámico Axial en probetas cilíndricas entalladas para medir el comportamiento a fatiga en mezclas asfálticas

Fatigue cracking is one of the most common damage mechanisms on the pavement structures. This phenomenon is associated to the damage produced by repetitive load application, whose load magnitude is lower than the maximum admissible resistance that the material may resist. Because of this, the continuous application of loads generated by the traffic creates a progressive damage in the pavement layers. Currently, there are different methodologies that allow predicting the fatigue cracking, but most of these methodologies are complex procedures which may not guarantee the failure of some types of mixtures and may not relate the applied load conditions to those suffered in the pavement. For this reason, to understand the fatigue craking behavior of asphalt mixtures is essential to develop effective fatigue tests. In this context, the main goal of this paper is to propose a test methodology to evaluate fatigue cracking by using a notched cylindrical asphalt concrete specimen. The proposed method allows reproducing the pavement tensional state, avoiding the stress dissipation, and focusing the strains in the middle of the previously groove carved specimen. A semi dense asphalt mixture gradation, used in asphalt pavement surface layer, were chosen. Three types of aggregates were evaluated, determining their fatigue laws. Besides, an analysis of durability of asphalt mixtures was presented.La fisuración por fatiga es uno de los mecanismos de deterioro más comunes en las estructuras de pavimentos. Este fenómeno está asociado al deterioro generado como consecuencia de la aplicación de cargas repetitivas cuya magnitud de carga es inferior a la resistencia máxima admisible que puede soportar el material. Por lo mismo, la aplicación continua de las cargas generadas por la acción del tránsito, dan lugar a un progresivo deterioro de las capas del pavimento. En la actualidad, existen distintas metodologías que permiten predecir la fisuración por fatiga, pero un gran número de estas se caracterizan por ser procedimientos complejos, y en muchas ocasiones no se garantizan la falla de algunos tipos de mezclas y/o no relacionan las condiciones de carga aplicadas con las sufridas en el pavimento. Es por esto, que el desarrollo de ensayos efectivos es fundamental para comprender el comportamiento frente a la falla por fatiga de las mezclas asfálticas. En este contexto, el artículo presentado tiene como objetivo principal proponer una metodología de ensayo para evaluar la fisuración por fatiga por medio del uso una probeta cilíndrica entallada. El método propuesto permite la reproducción del estado tensional del pavimento, evitando la disipación de esfuerzos, concentrando las tensiones en la zona intermedia de la probeta, previamente entallada. Para este procedimiento propuesto, se evaluaron tres tipos de áridos para una mezcla semidensa usualmente utilizada en capas de rodadura, determinándose las leyes de fatiga para cada mezcla. Además, se presenta un análisis de durabilidad de las mezclas evaluadas

Experimental Study to Design Warm Mix Asphalts and Recycled Warm Mix Asphalts Using Natural Zeolite as Additive for Sustainable Pavements

There are currently various technologies for the manufacture of warm mix asphalts (WMA). This paper presents the possibility of using a natural zeolite to manufacture WMA as an alternative to existing synthetic products for the manufacture of this type of mixture. Moreover, the possibility of manufacturing WMA with the addition of recycled asphalt pavement (RAP) using natural zeolite as the basis of a warm mix technology was evaluated. Firstly, asphalt mixtures were manufactured at three different temperatures (145 °C, 135 °C, and 125 °C) with different percentages of natural zeolite to determine the temperature and the optimum content for the manufacture of WMA. Then, the zeolite moisture content and its release over time were determined at different temperatures, and its distribution in the binder was checked at different concentrations by scanning electron microscopy and fluorescence. Next, with the optimum zeolite content, the addition of RAP between 10–30% in the WMA at the same three manufacturing temperatures was evaluated. Two types of compaction were used: the impact and gyratory compactions. The Marshall parameters were evaluated for all the designed mixtures. The results indicated that the manufacture of WMA with the addition of natural zeolite is feasible, and depending on the required mixing temperature, recycled WMA with different percentages of RAP can be obtained

Study of the Effect of the Use of Asphalt Binders Modified with Polymer Fibres from End-of-Life Tyres (ELT) on the Mechanical Properties of Hot Mix Asphalt at Different Operating Temperatures

Processing of end-of-life tyres (ELT) produces polymer fibres (PFELT) as a by-product. PFELT currently presents a challenge to the recycling industry, due to the increasing numbers of ELT and lack of alternatives for the re-use of this material. The object of this investigation was to propose an alternative for re-using PFELT, in order to improve the performance properties of hot mix asphalt (HMA). This study enabled us to understand the relation between the addition of polymer fibre to the aggregate-binder matrix of the HMA in depth, as well as its effects on the mechanical properties of the resulting asphalt mix. To do this, we first made a physical and chemical characterization of the PFELT (TGA, SEM, polarized light, and fluorescence microscopy), establishing a modification methodology using two asphalt binders (CA-24 and CA-14) and three PFELT contents (0.1%, 0.3%, and 0.5%). The HMA was designed using the Marshall method. The mechanical performance of the HMA was evaluated in a range of operating temperatures, from −10 °C to 50 °C, observing the following properties: (1) resistance to thermal cracking; (2) stiffness modulus; (3) indirect tensile strength; and (4) resistance to permanent deformation. The results show that the addition of 0.3% and 0.5% of PFELT to the asphalt binder significantly improved the mechanical performance properties of the mixes studied, with a greater effect at high operating temperatures; the resistance to permanent deformation increased by more than 30%

Effect of a New Additive Based on Textile Fibres from End-of-Life Tyres (ELT) on the Mechanical Properties of Stone Mastic Asphalt

Stone Mastic Asphalts (SMA) are asphalt mixes with discontinuous granulometry and a high content of asphalt binder. In order to prevent draindown of the asphalt binder and ensure good performance, these mixes must be strengthened with cellulose or mineral fibres and/or polymer additives. This study was designed to evaluate the effect of a granular additive based on waste tyre textile fibres (WTTF), developed as a replacement for cellulose commercial additives in SMA mixes. Use of the WTTF-based additive will encourage the development of sustainable mixes by recycling a by-product of end-of-life tyres (ELT), which currently constitute a major environmental problem around the world. To this end, in the present experimental study we evaluated the replacement of cellulose-based commercial fibre with different percentages of WTTF-based additive (0%, 50%, 75%, 100%) in an SMA asphalt mix. The following design and performance properties were evaluated: resistance to cracking, stiffness modulus, sensitivity to moisture, and resistance to permanent deformation. The results indicated that replacing 100% of the cellulose commercial additive in the SMA mix by the WTTF-based additive allowed the mix to meet its design properties and showed good performance in the mechanical properties evaluated, with behaviour similar to that of the reference SMA mix

Evaluación de las propiedades mecánicas de mezclas asfálticas con la incorporación de fibras sintéticas de aramida y polipropileno.

Roads are exposed to external conditions such as rain, solar radiation and the increase of vehicular flow, among others; which generates distresses on asphalt pavements. It is necessary to research new technologies being able to improve the behavior of pavements against external conditions. Currently, the use of polymer modified asphalts is one of the most used alternatives, because they provide a greater durability to the pavement structure. However, literature review has shown that there are other competitive techniques to obtain good results, such as the use of synthetic fibers. Therefore, the main objective of this research is to evaluate the influence of the addition of aramid and polypropylene synthetic fibers in the mechanical properties of asphalt mixtures.For this purpose, a IV-A-12 asphalt mixture (mainly used in Chile) with a CA-24 asphalt binder (according to Chilean specifications) were manufactured, incorporating different percentages of synthetic fibers. The mechanical properties of the modified asphalt mixtures were compared with a reference hot asphalt mixture. Through the experimental phase, thermal cracking, moisture damage and rutting properties were evaluated. The results have shown that the use of aramid and polypropylene fibers in asphalt mixtures reduced the moisture damage and rutting, nevertheless the thermal cracking was improved.Las carreteras están expuestas a agentes externos, como la lluvia, radiación solar, el aumento del flujo vehicular, entre otras, que contribuyen a generar deterioros en los pavimentos asfálticos. Esto hace necesaria la búsqueda nuevas tecnologías capaces de dar solución a estas condiciones externas. En la actualidad, la utilización de asfaltos modificados con polímeros es una de las alternativas más utilizadas, puesto que le otorga una mayor durabilidad a la estructura de pavimento. Sin embargo, la literatura indica que existen otras técnicas lo suficientemente competitivas que permiten la obtención de buenos resultados, como el uso de fibras sintéticas. En este contexto, la presente investigación tiene como objetivo principal evaluar la influencia de la incorporación de fibras sintéticas de aramida y polipropileno en las propiedades mecánicas de las mezclas asfálticas. Para ello, se realizó un diseño de una mezcla IV-A-12 (comúnmente utilizada en Chile) con un ligante tipo CA-2(de acuerdo a las especificaciones chilenas) con incorporación de diferentes porcentajes de fibras. Las propiedades mecánicas de las mezclas asfálticas modificadas fueron comparadas con una mezcla de referencia. A través de una fase experimental realizada, se evaluaron las propiedades de fisuración térmica, daño por humedad y el comportamiento frente a las deformaciones permanentes. Los resultados muestran que la adición de las fibras sintéticas de aramida y polipropileno reducen el daño por humedad y el ahuellamiento, mejorando también la respuesta frente a la fisuración térmica

Development of a New Additive Based on Textile Fibers of End-of-Life Tires (ELT) for Sustainable Asphalt Mixtures with Improved Mechanical Properties

End-of-life tires (ELT) are a worldwide problem. Rubber, steel, and different textile fibers are the by-products of ELT. Unlike rubber and steel, waste tire textile fibers (WTTF) are disposed of in landfills or burned. This study developed an additive made with WTTF to be incorporated into conventional hot mix asphalt (HMA), and its performance properties were evaluated. First, a characterization of the WTTF used was made and a manufacture protocol was established. Then, a reference HMA was designed and mixtures with different addition percentages (2%, 5% and 8%) of the WTTF-based additive were evaluated. The mechanical properties studied were stiffness modulus, moisture susceptibility, rutting resistance, stripping, and cracking resistance. The results indicated that the addition of the 2% and 5% WTTF-based additive improved these performance properties. Moreover, all addition percentages of the WTTF-based additive evaluated demonstrated a decrease of over 29% in permanent deformation according to the Hamburg Wheel Tracking Test. Thus, the use of the WTTF would not only be valuing a waste, but an asphalt mixture with improved properties would be obtained, contributing to the circular economy by reusing a material and prolonging the useful life of the asphalt mixture

Evaluación de las propiedades mecánicas de mezclas asfálticas con la incorporación de fibras sintéticas de aramida y polipropileno.

Roads are exposed to external conditions such as rain, solar radiation and the increase of vehicular flow, among others; which generates distresses on asphalt pavements. It is necessary to research new technologies being able to improve the behavior of pavements against external conditions. Currently, the use of polymer modified asphalts is one of the most used alternatives, because they provide a greater durability to the pavement structure. However, literature review has shown that there are other competitive techniques to obtain good results, such as the use of synthetic fibers. Therefore, the main objective of this research is to evaluate the influence of the addition of aramid and polypropylene synthetic fibers in the mechanical properties of asphalt mixtures.For this purpose, a IV-A-12 asphalt mixture (mainly used in Chile) with a CA-24 asphalt binder (according to Chilean specifications) were manufactured, incorporating different percentages of synthetic fibers. The mechanical properties of the modified asphalt mixtures were compared with a reference hot asphalt mixture. Through the experimental phase, thermal cracking, moisture damage and rutting properties were evaluated. The results have shown that the use of aramid and polypropylene fibers in asphalt mixtures reduced the moisture damage and rutting, nevertheless the thermal cracking was improved.Las carreteras están expuestas a agentes externos, como la lluvia, radiación solar, el aumento del flujo vehicular, entre otras, que contribuyen a generar deterioros en los pavimentos asfálticos. Esto hace necesaria la búsqueda nuevas tecnologías capaces de dar solución a estas condiciones externas. En la actualidad, la utilización de asfaltos modificados con polímeros es una de las alternativas más utilizadas, puesto que le otorga una mayor durabilidad a la estructura de pavimento. Sin embargo, la literatura indica que existen otras técnicas lo suficientemente competitivas que permiten la obtención de buenos resultados, como el uso de fibras sintéticas. En este contexto, la presente investigación tiene como objetivo principal evaluar la influencia de la incorporación de fibras sintéticas de aramida y polipropileno en las propiedades mecánicas de las mezclas asfálticas. Para ello, se realizó un diseño de una mezcla IV-A-12 (comúnmente utilizada en Chile) con un ligante tipo CA-2(de acuerdo a las especificaciones chilenas) con incorporación de diferentes porcentajes de fibras. Las propiedades mecánicas de las mezclas asfálticas modificadas fueron comparadas con una mezcla de referencia. A través de una fase experimental realizada, se evaluaron las propiedades de fisuración térmica, daño por humedad y el comportamiento frente a las deformaciones permanentes. Los resultados muestran que la adición de las fibras sintéticas de aramida y polipropileno reducen el daño por humedad y el ahuellamiento, mejorando también la respuesta frente a la fisuración térmica

Evaluation of Reductions in Fume Emissions (VOCs and SVOCs) from Warm Mix Asphalt Incorporating Natural Zeolite and Reclaimed Asphalt Pavement for Sustainable Pavements

Conventional asphalt mixtures used for road paving require high manufacturing temperatures and therefore high energy expenditure, which has a negative environmental impact and creates risk in the workplace owing to high emissions of pollutants, greenhouse gases, and toxic fumes. Reducing energy consumption and emissions is a continuous challenge for the asphalt industry. Previous studies have focused on the reduction of emissions without characterizing their composition, and detailed characterization of volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) in asphalt fumes is scarce. This communication describes the characterization and evaluation of VOCs and SVOCs from asphalt mixtures prepared at lower production temperatures using natural zeolite; in some cases, reclaimed asphalt pavement (RAP) was used. Fumes were extracted from different asphalt mix preparations using a gas syringe and then injected into hermetic gas sample bags. The compounds present in the fumes were sampled with a fiber and analyzed by gas-liquid chromatography coupled to mass spectrometry (GC/MS). In general, the preparation of warm mix asphalts (WMA) using RAP and natural zeolite as aggregates showed beneficial effects, reducing VOCs and SVOCs compared to hot mix asphalts (HMA). The fumes captured presented a similar composition to those from HMA, consisting principally of saturated and unsaturated aliphatic hydrocarbons and aromatic compounds but with few halogenated compounds and no polycyclic aromatic hydrocarbons. Thus, the paving mixtures described here are a friendlier alternative for the environment and for the health of road workers, in addition to permitting the re-use of RAP

Life Cycle Assessment of Natural Zeolite-Based Warm Mix Asphalt and Reclaimed Asphalt Pavement

Today, an important part of paved surfaces in the world uses asphalt mixtures. This practice increases the use of aggregates and fossil fuels, the availability of which is limited. Most of the studies referring to asphalt mixtures reported and compared the mechanical performances without detailing the environmental impacts of the different technologies proposed. The objective of this study was to present and compare through a life cycle assessment using a “cradle-to-gate” approach of different types of asphalt mixtures designed for the same performance, hot mix asphalt (HMA) as a control sample, and warm mix asphalt (WMA) using natural zeolite, Evotherm® and reclaimed asphalt material (RAP) in different proportions. The analysis was performed using SimaPro 9 software, using the ReCiPe method version 1.11. For the comparison of the environmental impacts, 1 ton of asphalt mixture was used as a functional unit. The most relevant results show that the use of natural zeolite or Evotherm® helps to reduce environmental impacts. In the global warming impact category, the decrease between the standard HMA and a mix with RAP and natural zeolite was 8%, while in the fossil fuel depletion, the decrease was 13%

Comparison of Environmental Loads of Fibers Used in the Manufacture of Hot Mix Asphalt (HMA) and Stone Mastic Asphalt (SMA) Mixes Using a Life Cycle Assessment (LCA)

Several authors have demonstrated improvements in the mechanical performance of asphalt mixes by including the use of fibers. However, it has also been reported that environmental assessments must address fiber use in asphalt mixes from the point of view of sustainability. In this study, a life cycle assessment is used to compare the use of four different fibers (fiberglass, polyester fiber, aramid fiber, and cellulose fiber) commonly used in hot mix asphalt (HMA) and stone mastic asphalt (SMA) mixes. Additionally, the use of textile fibers from end-of-life tires (FiTyre) is included in the comparison. The results show that in the five selected impact categories (climate change, terrestrial acidification, human toxicity, particulate matter emissions, and the exhaustion of nonrenewable fossil fuels), the use of FiTyre and cellulose fibers is more advantageous than existing traditional fibers (fiberglass, polyester fiber, and aramid fiber)