ABSTRACT:The interest in using bio-materials in pavement engineering has grown significantly over the last decades due to environmental concerns about the use of non-recoverable natural resources. In this paper, biomaterials are used together with Reclaimed Asphalt (RA) to restore some of the properties of the aged bitumen present in mixtures with high RA content. For this purpose, two bio-materials are studied and compared to conventional and polymer modified bitumens. Blends of these materials with RA bitumen were produced and studied to simulate a 50% RA mixture. The rejuvenating effect of the two bio-materials on RA has been assessed and compared with the effect of the conventional binders. Apparent Molecular Weight Distribution of the samples (obtained by the δ-method) and different rheological parameters were used for this purpose. Results revealed the power of bio-materials to rejuvenate RA bitumen, showing their capability to be used as fresh binders in high-RA content mixtures. RESUMEN:Evaluación del efecto rejuvenecedor de bio-materiales sobre ligantes para mezclas con alto contenido de asfalto recuperado. El interés en la utilización de bio-materiales en ingeniería de pavimentos ha crecido significantemente en las últimas décadas debido a la conciencia ambiental sobre el uso de recursos naturales no renovables. En este artículo, se utilizan bio-materiales para recuperar las propiedades iniciales del betún envejecido presente en mezclas con alto contenido de asfalto reciclado (RA). Para ello, se ha estudiado y comparado el comportamiento de dos bio-materiales con betunes convencionales y betunes modificados con polímeros. Con este objetivo, se fabricaron mezclas de bio-materiales y betún reciclado simulando mezclas asfálticas con 50% de contenido de reciclado. El efecto rejuvenecedor de los bio-materiales se ha evaluado y comparado con el efecto rejuvenecedor de ligantes convencionales mediante el cálculo de las distribuciones de peso molecular aparente y diferentes pará-metro reológicos. Los resultados muestran el poder rejuvenecedor de los bio-materiales, poniendo de manifiesto su potencial para usarse como ligantes vírgenes en mezclas asfálticas con alto contenido de reciclado.
ABSTRACT:The combination of high rates of reclaimed asphalt pavement (RAP) and warm mix asphalt (WMA) technologies is still ambiguous in terms of durability. With the aim of clarifying this issue, a study comparing a hot mix asphalt with a WMA prepared using the foaming process technology. Both mixes contain 50% of RAP and are submitted to a laboratory ageing procedure. The long term related performance of the mixtures is compared by means of complex modulus and fatigue testing. Penetration and ring and ball tests are undertaken on the recovered bitumens, as well as the ageing evolution, characterised by the Fourier Transform Infrared analysis. Finally, the Apparent Molecular Weight Distribution (AMWD) of the binders is calculated from rheological measurements using the δ-method. Results show a relation between ageing evolution and mechanical performance. After ageing, the overall tendencies are similar for both processes. RESUMEN: Evolución del envejecimiento en mezclas espumadas semicalientes con áridos reciclados.El comportamiento de mezclas asfálticas semicalientes (WMA) con alto contenido de material reciclado (RAP) es aún incierto a largo plazo. Por este motivo, en este estudio se compara el envejecimiento una mezcla caliente convencional y una mezcla espumada semicaliente con 50% de RAP. Ambas mezclas han sido sometidas a un proceso de envejecimiento en laboratorio. La respuesta a largo plazo se ha comparado a través de los ensayos de módulo de rigidez y de fatiga. En los betunes recuperados se han llevado a cabo los ensayos de penetración y anillo-bola, así como el seguimiento del envejecimiento a través del análisis de infrarrojos. Finalmente, la distribución de peso molecular aparente (AMWD) de los betunes se ha calculado a través de medidas reológicas usando el "δ-method". En los resultados se observa una relación entre la evolución del envejecimiento y su respuesta mecánica, donde la tendencia general es similar para ambas técnicas.
Within the framework of the European Project SUP&R ITN a PhD thesis is carried out to study the durability of the combination of high rates of reclaimed asphalt pavement and warm mix asphalt technologies. For this purpose the complex modulus and fatigue resistance of three different asphalt mixtures, including surfactant modified and foamed warm mix asphalts, combined with reclaimed asphalt pavement (RAP) has been studied. The extra value is given by the application of an ageing procedure based on the oxidation of compacted materials in laboratory. It follows the recommendations of the RILEM TC-ATB TG5, which distinguishes between short and long term ageing. Fourier Transform InfraRed (FTIR) tests were carried out on the extracted bitumens to quantify the oxidation levels. An increase of the norm and a decrease of the phase angle of |E*| at 15°C 10Hz with ageing and RAP addition are experienced for all the mixtures. Similar to what happens with the slopes of the fatigue laws that tend as well to increase. A consistent correlation is observed between these evolutions and the evolution of the carbonyl index calculated. This reflects a trend towards more brittle materials with predicted fatigue live improved for low strain levels but reduced for high strain levels. In general, the tendency is similar for all procedures, so the use of warm technologies combined with high RAP amounts may need to be considered.
This paper shows the results obtained in a research project that analyzes the mechanical performance of asphalt concrete containing waste glass as a substitute of part of the aggregate. The mechanical performance of an AC16S asphalt mix with different percentages of glass (0%, 8% and 15%) and different types of filler was assessed with the moisture sensitivity test, the stiffness modulus test, and the cyclic triaxial compression test in order to analyze their response to moisture action and plastic deformation as well as to calculate their stiffness modulus. Results show that the reuse of waste glass as a substitute for the sand fraction in low dosages (8%) produced asphalt mixes with mechanical properties that were suitable for road surfaces course, being the calcium carbonate the more appropriate filler.
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