h i g h l i g h t s Effects of different natural asphalts on the properties of HMAs were compared. SBS modified mixtures also compared with natural asphalt modified mixtures. Control and modified mixtures were subjected to HMA performance tests. All modifiers increased to resistance to permanent strain and fatigue crac ks.
Styrene-butadiene-styrene (SBS) polymer is one of the most preferred additives to improve performance in hot mix asphalt pavements. The storage instability, in other words, the separation of a polymer-rich phase from the bitumen-rich phase in the course of storage and transportation is one of the prevalent problems in SBS modified bitumen. The present study attempted to obtain modified bitumen at the same performance level with the SBS modified bitumen, but stable with respect to the storage stability. For this purpose, both SBS and American Gilsonite (AG) were used in modified bitumen production. It was determined that modified bitumen at the same performance level was obtained with the use of 5 % SBS or 18 % AG in bitumen modification. It was also determined that the performance levels of the modified bitumen obtained with the use of 2 % SBS + 13 % AG, 3 % SBS + 10 % AG and 4 % SBS + 6 % AG were similar. Additionally, 2 %, 3 % and 4 % SBS modified bitumen were used for the assessment of storage stability properties of the SBS modified binders. These 8 different modified bitumen samples were tested for storage stability based on the EN 13399 standard. Penetration, softening point, rotational viscometer, bending beam rheometer, and dynamic shear rheometer tests were conducted on the samples. Based on all conducted tests, it was determined that more stable binders were obtained with the use of AG and SBS in terms of storage stability compared to solely SBS modified bitumen.
Bu çalışmada iki farklı boyutta (No.40 elek üstü ve altı) öğütülmüş araç lastiği (CR) ve öğütülmüş araç lastiğinin pirolizinden elde edilen karbon siyahı bitüm modifikasyonunda 3 farklı oranda (%5, %10 ve %15) kullanılmıştır. Saf ve modifiye bağlayıcılar üzerinde penetrasyon, yumuşama noktası, viskozite ve dinamik kayma reometresi (DSR) deneyleri uygulanmıştır. Ayrıca bağlayıcıların sıcaklığa karşı hassasiyetinin göstergesi olan penetrasyon indeksi (PI) değerleri belirlenmiştir. Penetrasyon, yumuşama noktası ve viskozite deneyleri sonucunda bitüm modifikasyonunda kullanılan CR miktarı arttıkça penetrasyon değerlerinin düzenli olarak azaldığı, yumuşama noktası ve viskozite değerlerinin düzenli olarak arttığı belirlenmiştir. Bu durum CR kullanımının bitümün rijitliğini arttırdığını göstermektedir. CR boyutu değerlendirildiğinde malzeme boyutunun bu üç deney üzerinde önemli bir etkiye sahip olmadığı belirlenmiştir. PI değerlerinden saf bitümlü bağlayıcıya kıyasla No.40 elek altı %5 CR kullanılan modifiye bitüm dışındaki tüm modifiye bitümlerin sıcaklığa karşı hassasiyetinin daha az olduğu belirlenmiştir. DSR deneyleri sonucunda CR içeriği arttıkça bağlayıcıların tekerlek izine karşı dayanım parametrelerinin ve elastikiyetlerinin arttığı belirlenmiştir. Öğütülmüş CR'nin pirolize tabi tutulmasından elde edilen karbon siyahının bitüm modifikasyonunda kullanılması CR'nin etkinliğini azaltmış özellikle No.40 altı boyuttaki CR'nin karbon siyahı saf bitümün özelliklerini iyileştirme özelliği göstermemiştir.
In this study, the resistance of hot mix asphalts containing different additives to the creep permanent deformation was investigated by the dynamic creep test. Four different additives were used in the study. Styrene-butadiene-styrene (SBS), American Gilsonite (AG), and Iranian Gilsonite (IG) were used for modifying the bitumen. Additionally, the same mixtures were prepared by using 2% hydrated lime as filler. The samples were subjected to dynamic creep test at 50°C under 500 kPa stress level. As a result of the tests performed, it has been determined that all of the additives used in the study improve the resistance to the creep permanent deformation. It has also been determined that the use of bitumen additives is more effective than the use of lime. Furthermore, it has been determined that the most effective additive is IG while the least effective additive is SBS, and hydrated lime use is more effective compared to the mixtures prepared with a neat binder.
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