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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.

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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.

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Recently, crumb rubber (CR) obtained from waste tires and Fischer–Tropsch paraffin are mostly used in bitumen modification to improve the performance of bituminous mixtures. Each of these additives affects the different properties of mixtures. There are limited studies in the literature about the combined usage of additive in the same mixture to utilize the different characteristics. In this study, the stability, stiffness, fatigue resistance, permanent deformation resistance, and moisture susceptibility characteristics of the stone mastic asphalt prepared with the bitumen modified with CR and paraffin were examined and compared with the control mixture. It was determined that CR-modified mixtures showed significantly more elastic characteristics. The mixture in which the 10% CR and 3% paraffin were used together gave better results in terms of moisture susceptibility and fatigue resistance when compared with the control mixture. It was determined that the use of paraffin together with CR contributed to the improved performance, and was in accordance with the CR in terms of mechanical characteristics of stone mastic asphalt.

The method applied most to improve engineering properties of bituminous hot mixtures which are used in coating layer is the enhancement of bitumen's properties with various additive materials. Polymer based additive materials are generally used for bitumen modification. Among these additive materials, styrene-butadiene-styrene (SBS) block copolymers are mostly used. It was determined that SBS increases the resistance of mixtures against to rutting and fatigue at high temperatures. However it was determined that increased content of SBS caused both worsening of the low service temperature and also workability of the mixtures. It is reported that a rubbery network is created which improves elastic response and enhance low temperature cracking resistance in case the SBS-rich phase forms. It is known that using paraffin's property of reducing viscosity and increasing softening point together with SBS modification which causes increase in viscosity, enhances this combined binder's properties of high temperatures and workability; however there exists no study related to the behavior of this combined binder at low temperatures, in literature. In this study the effect of SBS and paraffin modification on base bitumen were investigated. Firstly the bitumen modified individually with SBS and paraffin was evaluated in terms of Bending Beam Rheometer (BBR) test. Then, the bitumen including both SBS and paraffin in different contents was tested. Including the three different SBS and paraffin content and also base bitumen, totally 16 different combination were evaluated. In conclusion, it was determined that the ratio of stiffness to m-value gives better result in evaluation of low temperature behavior. At low temperatures, it was determined that stiffness increase with increasing additive rates; however this increase is much more in paraffin modification, in particular, SBS addition at low ratio decreases the increase of stiffness caused by paraffin modification.