Taner Alataş

Evaluation of the Mechanical Properties of Field- and Laboratory-Compacted Hot-Mix Asphalt

The aim of this study is to investigate the effects of field-compaction conditions on the mechanical properties of asphalt concrete and then compare the properties with those of the specimens prepared with different Marshall hammer–blow numbers and gyratory-compactor gyrations. For this purpose, a binder layer was constructed with different compaction levels at different temperatures over a preconstructed plant-mix base layer. The B 70/100 bitumen and dense-graded limestone aggregate with a maximum size of 25.4 mm were used. The binder layer was divided into 12 sections, which were constructed with four different road roller–pass numbers and three different temperatures. The laboratory compaction conditions simulating all of the field compactions were assessed in indirect tensile strength, indirect tensile stiffness modulus, indirect tensile repeated load, and dynamic-creep tests. It was concluded that the field and laboratory specimens were affected by the compaction level and temperature in different ways. Furthermore, the specimens exhibited different performances even with the same air-void contents. The laboratory specimens with the same air-void contents as those of field specimens displayed much better performance than the field specimens.

Effects of different bitumen modifiers on the rutting and cracking resistance of hot mix asphalts

ABSTRACT In this study, four different additives (Styrene–butadiene–styrene (SBS), Trinidad Lake Asphalt (TLA), Iranian Gilsonite (IG) and American Gilsonite (AG)) were used in bitumen modification. The rheological properties of bitumen were improved with the additive usage, and the desired performance grade (PG 70-34) was achieved by using additives in pure bitumen (PG 58-34) at the indicated ratios. Wheel tracking tests and semi-circular bending tests were applied for hot mix asphalt (HMA) samples. The main results showed that all the additives increased resistance to permanent deformation of HMAs, and that TLA was the most effective additive. In addition, it was found from the semi-circular bending tests that deformation values of mixtures prepared with modified bitumens and subjected to long-term ageing decreased. As a result, long-term aged and modified bitumen mixtures exhibited more brittle behaviour. The increase in maximum load values led to an increase in the area under the load-strain curves. Thus, crack propagation resistance of mixtures prepared with modified binders was increased.

Low temperature properties of hot mix asphalts prepared with different polymer modified binders

U radu se analizira otpornost čistih i polimerima modificiranih mješavina na širenje pukotina pri niskim temperaturama primjenom linearne i nelinearne mehanike loma. Razmatran je utjecaj dva veziva za modificiranje bitumena: stiren-butadien-stiren (SBS) i etilen-vinil-acetat (EVA). Ispitivanja su pokazala da pri padu temperature rastu vrijednosti lomne žilavosti, a smanjuju se vrijednosti maksimalne vertikalne deformacije. Ustanovljeno je da je u oba postupka primijenjena u ovom radu najniža vrijednost lomne žilavosti dobivena primjenom veziva EVA.The low temperature crack propagation resistance of pure and polymer modified mixtures is analysed in the paper by means of linear and nonlinear fracture mechanics. The influence of two bitumen-modification binders is considered: styrene-butadienestyrene (SBS) and ethylene-vinyl-acetate (EVA). The experiments demonstrated that the fracture toughness values increase, and the maximum vertical strain values decrease, with a decrease in temperature. It was established by both techniques used in the paper that the lowest fracture toughness was obtained using the EVA binder.

Niskotemperaturna svojstva vrućih asfaltnih mješavina s različitim polimerom modificiranim vezivima

U radu se analizira otpornost čistih i polimerima modificiranih mješavina na širenje pukotina pri niskim temperaturama primjenom linearne i nelinearne mehanike loma. Razmatran je utjecaj dva veziva za modificiranje bitumena: stiren-butadien-stiren (SBS) i etilen-vinil-acetat (EVA). Ispitivanja su pokazala da pri padu temperature rastu vrijednosti lomne žilavosti, a smanjuju se vrijednosti maksimalne vertikalne deformacije. Ustanovljeno je da je u oba postupka primijenjena u ovom radu najniža vrijednost lomne žilavosti dobivena primjenom veziva EVA.The low temperature crack propagation resistance of pure and polymer modified mixtures is analysed in the paper by means of linear and nonlinear fracture mechanics. The influence of two bitumen-modification binders is considered: styrene-butadienestyrene (SBS) and ethylene-vinyl-acetate (EVA). The experiments demonstrated that the fracture toughness values increase, and the maximum vertical strain values decrease, with a decrease in temperature. It was established by both techniques used in the paper that the lowest fracture toughness was obtained using the EVA binder.