A presença de aditivos incorporadores de ar (AIA) em suspensões cimentícias torna esses materiais sensíveis às etapas de processamento e às condições ambientais de preparo das composições. Diversos estudos têm sido reportados em literatura avaliando o efeito de incorporadores de ar nas propriedades de materiais cimentícios, sobretudo no estado endurecido. Porém o efeito da temperatura na incorporação de ar e nas propriedades reológicas dessas composições tem sido menos investigado, sendo este o objetivo do presente trabalho. Para tanto, foram avaliadas as características de pastas cimentícias, compostas por cimentos CPIIF ou CPIIE e dois tipos de AIA, em função da variação da temperatura. O conceito de viscosidade cinemática foi adotado na análise dos resultados para compensar diferenças de inércia das pastas com densidades distintas. Os resultados mostraram que o tipo de cimento, a presença do aditivo e a temperatura influenciaram significativamente na incorporação de ar e nas propriedades reológicas.
The addition of polymers on asphalt binders aims to enhance their performance, especially at high temperatures, which correspond to rutting resistance. The Superpave rutting parameter (|G*|/sinδ) has been considered to be inadequate to characterize the performance of modified materials, therefore the Multiple Stress Creep and Recovery (MSCR) test was developed, providing the parameter non-recoverable compliance (Jnr). This research has the main objective of correlating asphalt binders performance-based characterization with rutting resistance of asphalt mixtures, and presents results obtained for one conventional (50/70 penetration grade) and two modified asphalt binders (2.1% RET and 1.9% RET) regarding their rheological characteristics. With the use of the dynamic shear rheometer (DSR), master curves and MSCR results were obtained for the three binders. In addition, permanent deformation tests were performed on the asphalt mixtures by means of laboratory traffic simulation. The rutting characterization indicated higher permanent deformation resistance for the modified binders for the asphalt binder and the asphalt mixture testing. The main conclusions were that the use of modified binder reduced in approximately 50% the Jnr values and the rut depth; also, the asphalt binders’ characteristics were able to predict the asphalt mixtures rutting resistance.
The aging and rejuvenation of two neat asphalt binders were evaluated in this study.Both binders are from an experimental section that was built with dense hot asphalt mixtures of the two binders, with 4 cm thick. The binders were extracted and recovered from the samples collected from the experimental sections at different times (T = 0, 12, 24, 36 and 108 months after the pavement construction). In the laboratory, the virgin binders were aged using RTFOT, PAV 20h, PAV 60h and SUNTEST. Rheological frequency sweep tests were carried out, as well as the analysis of the parameters G*c, ωc, R and GR. In addition, MSCR and LAS tests were carried out to evaluated the resistance to permanent deformation and to fatigue, respectively, of both binders at different levels of aging and rejuvenation. The SARA fraction, GPC, FTIR and NMR tests were performed to evaluate the chemical changes resulting from laboratory and field aging. The results show that the SUNTEST aging was the most severe, showing the importance of UV radiation in the aging process of asphalt binders. In addition, photochemical aging causes different chemical reactions in the asphalt binders when compared to thermo oxidative aging, with different impact on chemical fractions of the two binders evaluated. In the field, binders continued to age over time, resulting in chemical and performance changes in asphalt binders. The comparison between laboratory and field aging showed that aging in the field (after 36 months) was more severe than the PAV 20h, and the results were closer to PAV 60h, for both binders.The use of pine-based rejuvenating agent with 2%, 4% and 6% content, showed that the AR allowed to recover most of the properties of the aged binders with 4% of AR.However, rejuvenation follows a different trend from aging, showing that AR acts differently on the viscoelastic properties of aged binders. In addition, the AR dosage evaluation using different parameters showed that the dosage only through binder's linear viscoelastic properties may not be sufficient to guarantee the final performance of the recycled mixtures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.