Baha Vural Kök

Investigation of complex modulus of base and SBS modified bitumen with artificial neural networks

This study aims to model the complex modulus of base and styrene-butadiene-styrene (SBS) modified bitumens by using artificial neural networks (ANNs). The complex modulus of base and SBS polymer modified bitumen samples (PMB) were determined by using dynamic shear rheometer (DSRs). PMB samples have been produced by mixing a 50/70 penetration grade base bitumen with SBS Kraton D1101 copolymer at five different polymer contents. In ANN model, the bitumen temperature, frequency and SBS contents are the parameters for the input layer where as the complex modulus is the parameter for the output layer. The variants of the algorithm used in the study are the Levenberg-Marquardt (LM), scaled conjugate gradient (SCG) and Pola-Ribiere conjugate gradient (CGP) algorithms. A tangent sigmoid transfer function was used for both hidden layer and the output layer. The statistical indicators, such as the root-mean squared (RMS), the coefficient of multiple determination (R^2) and the coefficient of variation (cov) was utilized to compare the predicted and measured values for model validation. The analysis indicated that the LM algorithm appeared to be the most optimal topology which gained 0.0039 mean RMS value, 20.24 mean cov value and 0.9970 mean R^2 value.

Investigation of complex modulus of base and EVA modified bitumen with Adaptive-Network-Based Fuzzy Inference System

This study aims to model the complex modulus of base and ethylene-vinyl-acetate (EVA) modified bitumen by using Adaptive-Network-Based Fuzzy Inference System (ANFIS). The complex modulus of base and EVA polymer modified bitumen (PMB) samples were determined using dynamic shear rheometer (DSR). PMB samples have been produced by mixing a 50/70 penetration grade base bitumen with EVA copolymer at five different polymer contents. In ANFIS modeling, the bitumen temperature, frequency and EVA content are the parameters for the input layer and the complex modulus is the parameter for the output layer. The hybrid learning algorithm related to the ANFIS has been used in this study. The variants of the algorithm used in the study are two input membership functions and three input membership functions for each of the all inputs. The input membership functions are triangular, gbell, gauss2, and gauss. The results showed that EVA polymer modified bitumens display reduced temperature susceptibility than base bitumens. In the light of analysis the Adaptive-Network-Based Fuzzy Inference System and statistical methods can be used for modeling the complex modulus of bitumen under varying temperature and frequency. The analysis indicated that the training accuracy is improved by decreasing the number of input membership functions and the utilization of the two gauss input membership functions appeared to be most optimal topology. Besides, it is realized that the predicted complex modulus is closely related with the measured (actual) complex modulus.

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.

Investigation of Mechanical Properties of Short- and Long-Term Aged Asphaltite Modified Asphalt Mixtures

AbstractIn this study, the effects of asphaltite and long-term aging (LTA) on the mechanical properties of hot-mix asphalt were investigated. The asphaltite entrained as filler at five different proportions into the hot-mix asphalt samples, and the obtained results were compared against the control mixtures. The pure and asphaltite-containing compacted mixtures were exposed to LTA in an oven. Marshall stability, resistance to moisture-induced damage, and resistance to crack propagation tests in accordance with the principles of elastic-plastic fracture and linear-elastic fracture mechanics were carried out on the mixtures. It was determined that the optimal proportion of asphaltite usage as filler with respect to volumetric design is 3% by weight. The test results demonstrated that asphaltite use enhances resistance against permanent deformation, moisture-induced damage, and crack propagation, especially at normal temperatures, albeit at the cost of causing the hot-mix asphalt to exhibit a more brittle be...

Evaluation of the mechanical properties of natural asphalt-modified hot mixture

Abstract The objective of this study is to evaluate the usage of natural asphalt in hot mix asphalt by means of determining the Marshall stability, stiffness modulus, indirect tensile strength, and dynamic creep tests. Natural asphalt, which consists of 17% asphalt fraction and 83% mineral fraction, was obtained from Syrian. The optimum bitumen content was determined to be 1% lower for natural asphalt-modified mixtures compared to control mixtures. The stiffness modulus values of the natural asphalt-modified mixtures were higher than those of the control mixtures. The moisture susceptibility of natural asphalt-modified mixtures and control mixtures were evaluated during different freeze–thaw cycles. The natural asphalt-modified mixtures were not as susceptible as control mixtures to moisture damage. Adding natural asphalt to mixtures remarkably decreased susceptibility to permanent deformation. The results presented here demonstrate the positive effects of using natural asphalt.

ÖĞÜTÜLMÜŞ ARAÇ LASTİĞİNİN VE PİROLİZ İŞLEMİNDEN SONRA OLUŞAN KARBON SİYAHININ BİTÜMLÜ BAĞLAYICILARIN REOLOJİK ÖZELLİKLERİ ÜZERİNDEKİ ETKİSİ

Bu calismada iki farkli boyutta (No.40 elek ustu ve alti) ogutulmus arac lastigi (CR) ve ogutulmus arac lastiginin pirolizinden elde edilen karbon siyahi bitum modifikasyonunda 3 farkli oranda (%5, %10 ve %15) kullanilmistir. Saf ve modifiye baglayicilar uzerinde penetrasyon, yumusama noktasi, viskozite ve dinamik kayma reometresi (DSR) deneyleri uygulanmistir. Ayrica baglayicilarin isiya karsi hassasiyetinin gostergesi olan penetrasyon indeksi (PI) degerleri belirlenmistir. Penetrasyon, yumusama noktasi ve viskozite deneyleri sonucunda bitum modifikasyonunda kullanilan CR miktari arttikca penetrasyon degerlerinin duzenli olarak azaldigi, yumusaman noktasi ve viskozite degerlerinin duzenli olarak arttigi belirlenmistir. Bu durum CR kullanimi ile bitumun rijitliginin arttigini gostermektedir. CR boyutu degerlendirildiginde malzeme boyutunun bu uc deney uzerinde onemli bir etkiye sahip olmadigi belirlenmistir. PI degerlerinden saf baglayiciya kiyasla No.40 elek alti %5 CR kullanilan modifiye bitum disindaki tum modifiye bitumlerin isiya karsi hassasiyetinin daha az oldugu belirlenmistir. DSR deneyleri sonucunda CR icerigi arttikca baglayicilarin tekerlek izine karsi dayanim parametrelerinin ve elastikiyetlerinin arttigi belirlenmistir. Ogutulmus CR’nin pirolize tabi tutulmasindan elde edilen karbon siyahinin bitum modifikasyonunda kullanilmasi, CR’nin etkinligini azaltmis ozellikle No.40 alti boyuttaki CR’nin karbon siyahi saf bitumun ozelliklerini iyilestirme ozelligi gostermemistir.

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.

Effects of graphite on mechanical properties of stone mastic asphalt pavement

AbstractHot mix asphalt needs to be developed to resist particular permanent deformations like rutting and thermal cracking due to increased traffic volumes and vehicle loads. Additives such as carbon black, graphite, carbon fibers are used in the mixture or the binder for improving the mechanical features of asphalt. In this article, the effects of graphite used for developing the mechanical properties of asphalt have been investigated in mixtures tests. Therefore, Marshall stability, indirect tensile stiffness modulus and indirect tensile fatigue tests were performed to bituminous mixtures modified with three different proportions of graphite by weight of bitumen. Stone mastic asphalt mixtures which were manufactured with pure and modified bitumen were aged in different time intervals in the oven. In conclusion, it has defined that Marshall stability values have declined. It has been determined that there is no significant difference in the time-dependent deformation behavior of the original and aged sa...

Effect of CR and FT-paraffin versus SBS modification in terms of conventional and rheological properties

Abstract In this study, the rheological and conventional properties of binders prepared with crumb rubber (CR) and FT-paraffin were compared to styrene-butadiene-styrene (SBS)-modified binders’ properties. The objective of this study was to determine which modified binders in different combinations of the CR and the FT-paraffin exhibited better performance than the SBS-modified binders, in terms of conventional and rheological properties. Results showed that the additives exhibited different performances for different types of tests. Many of the combinations including the common usage of the CR and the FT-paraffin performed better at high temperature than the SBS modification. Overall, the test results show that the binders prepared by 6% CR with 3 and 4% FT-paraffin and those prepared with 8% CR with 3% FT-paraffin were better binders than the 4% SBS-modified binder, in terms of low and high temperature properties.

Effects of nanoclay modification on the rheological properties of bituminous binders

The rheological behavior of bitumen is very complex phenomenon varying from purely viscous to elastic depending on loading time and temperature. As a visco-elastic material, bitumen plays a prominent role in determining many aspects of road performance. Numerous investigations have been carried out on incorporating modified bitumens to improve the performance of bituminous composites. This paper presents a laboratory-scale evaluation of the conventional and the fundamental rheological characteristics of modified binders including nanoclay contains 35-45 wt. % dimethyl dialkyl (C14-C18) amine (DANC) and montmorillonite. Modified bitumen samples were produced by mixing base bitumen with DANC and montmorillonite at three different additive contents. The conventional properties of the modified binders were evaluated in terms of their properties using penetration, softening point and dynamic viscosity tests. The fundamental viscoelastic properties of the modified binders were determined using dynamic (oscillatory) mechanical analysis and were presented in the form of temperatureand frequencydependent rheological parameters. It was determined by the results obtained from the conventional tests that the softening point and the viscosity increased and the penetration and the thermal sensitivity decreased with increased DANC. Dynamic shear rheometer test results indicated that the temperature and the frequency had a significant effect on the complex modulus of DANC and montmorillonite modified binders. The research results are an indication that the DANC has promising potential to reduce the permanent deformation or rutting of asphalt pavements. Investigation of the types of different additives yielded that the most effective additive was DANC in all experiments.