The growth of the world population has increased the production of wastes. These are generally incinerated or deposited in outdoor landfills, which impacts the environment and affects human health. A technique that allows to reuse of wastes and diminishes adverse effects on the environment is pyrolysis. Through this technique, a material known as Biochar (BC) is produced, which has proven to have interesting physical-chemical properties for it to be used as an asphalt modifier, and simultaneously, helps to mitigate negative impacts on the environment. The foregoing article presents a bibliographical review on the use of BC as a modifier for asphalt binders and asphalt mixes. This has the purpose of becoming a starting point for future research efforts. In the reviewed literature, there was no review found on this topic. In general terms, BC increases the performance of asphalt binders in high-temperature climates, and tends to reduce its performance in low-temperature ones. Few studies have evaluated the performance of BC on asphalt mixes and the long-term properties associated with durability. Based on the reviewed literature, at the end of the article, recommendations are provided for future study topics.
The use of polymeric waste in the modification of asphalt binders for the construction of road pavements is a technique studied several years ago. However, the use of these materials involves high temperatures close to 190 °C, which generate large environmental impacts due to their emissions. In this study, an asphalt cement (AC) with low-density polyethylene (LDPE) residue contents of 5%, 7%, and 10% with respect to the mass of the AC was modified by the wet method. The modification was carried out using a temperature of 150 °C with the aim of preventing the oxidation of the AC and reducing the emissions generated at high temperatures. Based on the physical-rheological properties of the modified asphalt binder, it was found that 5% LDPE produces the best performance. Subsequently, a hot-mix asphalt type HMA-19 control without a modified asphalt binder and another with a modified asphalt binder were manufactured in order to evaluate the mechanical behavior by means of the Marshall test, an indirect tensile strength (ITS) test, resilient modulus (RM) testing, resistance to fatigue testing, permanent deformation testing, and the Cantabro test. Additionally, the asphalt mixtures were tested under the conditions of short-term aging (STOA, Short-Term Oven Aging), long-term aging (STOA + LTOA, Long-Term Oven Aging), and partial saturation with water (STOA + LTOA + water). Based on the results, an ANOVA analysis of variance was performed to assess whether the changes in the mechanical response of the modified mixture are statistically significant with respect to the control mixture. As a general conclusion, it is reported that mixtures with LDPE can be used for thick layers in high-temperature climates in order to control rutting.
This article evaluates in the laboratory the physical and rheological properties of the modified asphalt cement (AC) with different contents of rubber (R) from used military boots. For the evaluation of the modified AC, laboratory tests of penetration, softening point, ductility, viscosity, short-term aging and determination of the rheological parameters in the DSR dynamic shearing rheometer were performed. In addition, the mechanical performance of a conventional asphaltic dense mixture (control) and three dense asphalt mixtures with modified asphalt cement with different rubber contents, wet-added, was evaluated by means of monotonic load tests (Marshall Stability) and dynamic (dynamic module). The physical and rheological evaluation of the AC modified with R indicates a significant increase in stiffness as a function of the R content. The asphalt mixtures studied, in reference to the control mixture, presented the same optimum content of asphalt and an increase in the Mar-shall rigidity and dynamic module. Therefore, it was found that the addition of rubber from military boots used in the asphalt cement and later in the mixture, can be considered viable from the technical and environmental point of view, due to the improvement in the mechanical properties of these materials and to allow a form of correct final disposal of the rubber.
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