Publicação
Evaluation of polymer modified asphalt binder aging
| Resumo: | Asphalt binders used in road pavements basically age in two phases, the short-term aging and the long-term aging. Short-term aging occurs in binders due to mixing, transporting, placing, and compaction of asphalt mixtures, while long-term aging occurs in situ during the lifetime of the pavement. The effect of short-term and long-term aging on the binder reveals in its chemical structure, mainly by increasing the rate of oxidation, and in its physical or rheological properties by hardening. The main aim of this work was the study of the short-term aging, especially addressing the assessment of polymer modified asphalt binders. In fact, these binders are being increasingly used, but the evolution of their properties during aging is still not well known. A 35/50 penetration grade unmodified bitumen (B1), a 70/100 penetration grade Ethylene Vinyl Acetate (EVA)-modified bitumen (PmB1), and a 70/100 penetration grade High-Density Polyethylene (HDPE)-modified bitumen (PmB2) were aged applying two different methods. In one method, the binders were exposed to 75-min in RTFOT testing (binder aging). In the other method, the binders were used to produce asphalt mixture samples, and the aged binders were recovered (short-term aging of the mixture and binder recovery) after mechanical testing of samples. The rheological properties of all binders were assessed for each one of their states, namely unaged, after-RTFOT aging, and after-recovery aging. These rheological measurements after RTFOT aging obviously indicated an increase in the binders’ stiffness. However, the rheological results after-recovery appeared to be unreasonable. Hence, the binders PmB1 and PmB2 were also subjected to DSC testing trying to explain these unexpected results. DSC analysis indicated that the polymers were absent from PmBs after recovery process. Yet, the FTIR analysis had demonstrated that the recovered bituminous parts of PmBs were indeed aged chemically when the mixtures were produced and compacted. |
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| Autores principais: | Ashqar, Huthaifa Issam |
| Assunto: | Short-term aging Polymer modified bitumen Rheological properties Recovered binder Envelhecimento a curto prazo Betume modificado com polímero Propriedades reológicas Ligante recuperado |
| Ano: | 2015 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Asphalt binders used in road pavements basically age in two phases, the short-term aging and the long-term aging. Short-term aging occurs in binders due to mixing, transporting, placing, and compaction of asphalt mixtures, while long-term aging occurs in situ during the lifetime of the pavement. The effect of short-term and long-term aging on the binder reveals in its chemical structure, mainly by increasing the rate of oxidation, and in its physical or rheological properties by hardening. The main aim of this work was the study of the short-term aging, especially addressing the assessment of polymer modified asphalt binders. In fact, these binders are being increasingly used, but the evolution of their properties during aging is still not well known. A 35/50 penetration grade unmodified bitumen (B1), a 70/100 penetration grade Ethylene Vinyl Acetate (EVA)-modified bitumen (PmB1), and a 70/100 penetration grade High-Density Polyethylene (HDPE)-modified bitumen (PmB2) were aged applying two different methods. In one method, the binders were exposed to 75-min in RTFOT testing (binder aging). In the other method, the binders were used to produce asphalt mixture samples, and the aged binders were recovered (short-term aging of the mixture and binder recovery) after mechanical testing of samples. The rheological properties of all binders were assessed for each one of their states, namely unaged, after-RTFOT aging, and after-recovery aging. These rheological measurements after RTFOT aging obviously indicated an increase in the binders’ stiffness. However, the rheological results after-recovery appeared to be unreasonable. Hence, the binders PmB1 and PmB2 were also subjected to DSC testing trying to explain these unexpected results. DSC analysis indicated that the polymers were absent from PmBs after recovery process. Yet, the FTIR analysis had demonstrated that the recovered bituminous parts of PmBs were indeed aged chemically when the mixtures were produced and compacted. |
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