Burak Sengoz

Evaluation of steel slag coarse aggregate in hot mix asphalt concrete

This paper presents the influences of the utilization of steel slag as a coarse aggregate on the properties of hot mix asphalt. Four different asphalt mixtures containing two types of asphalt cement (AC-5; AC-10) and coarse aggregate (limestone; steel slag) were used to prepare Marshall specimens and to determine optimum bitumen content. Mechanical characteristics of all mixtures were evaluated by Marshall stability, indirect tensile stiffness modulus, creep stiffness, and indirect tensile strength tests. The electrical sensitivity of the specimens were also investigated in accordance with ASTM D257-91. It was observed that steel slag used as a coarse aggregate improved the mechanical properties of asphalt mixtures. Moreover, volume resistivity values demonstrated that the electrical conductivity of steel slag mixtures were better than that of limestone mixtures.

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.

Utilization of Recycled Asphalt Concrete with Warm Mix Asphalt and Cost-Benefit Analysis

The asphalt paving industries are faced with two major problems. These two important challenges are generated with an increase in demand for environmentally friendly paving mixtures and the problem of rapidly rising raw materials. Recycling of reclaimed asphalt pavement (RAP) is a critical necessity to save precious aggregates and reduce the use of costly bitumen. Warm Mix Asphalt (WMA) technology provides not only the option of recycling asphalt pavement at a lower temperature than the temperature maintained in hot mixtures but also encourages the utilization of RAP and therefore saves energy and money. This paper describes the feasibility of utilizing three different WMA additives (organic, chemical and water containing) at recommended contents with different percentages of RAP. The mechanical properties and cost-benefit analysis of WMA containing RAP have been performed and compared with WMA without RAP. The results indicated that, 30%, 10% and 20% can be accepted as an optimum RAP addition related to organic, chemical and water containing additives respectively and organic additive with 30% RAP content has an appreciable increase in tensile strength over the control mix. It was also concluded that the RAP with WMA technology is the ability to reduce final cost compared to HMA and WMA mixtures.

Investigation of the rheological properties of elastomeric polymer-modified bitumen using warm-mix asphalt additives

In recent years, warm-mix asphalt (WMA) is extensively used in the hot-mix asphalt industry for reducing energy requirements and emissions by lowering mixing and compaction temperatures of bitumen. In addition, the use of polymer-modified bitumen (PMB) has become a very important part of pavement construction due to its superior performance, including less ageing, enhanced rutting resistance and lower fatigue cracking properties. This paper presents an experimental evaluation of elastomeric PMB involving WMA additives. In scope of the study, base bitumen has been modified with three different concentrations of styrene–butadiene–styrene (SBS) copolymer. The prepared PMB samples have been mixed with organic and chemical types WMA additives. Following the determination of the conventional properties as well as the rheological properties of the samples using dynamic shear rheometer, rutting behaviour of bitumen samples has been evaluated by zero shear viscosity test. The results of conventional bitumen tests showed a decrease in temperature susceptibility in PMB involving WMA additives. Based on the rheological test results, it was observed that the utilisation of organic WMA additive into PMB improves rutting performance of the modified bitumen especially in the 4% concentration of SBS copolymer.

Investigation of rheological effects of waxes on different bitumen sources

Wax in bitumen has been referred to as petroleum wax and is obtained from refining of paraffinic crude oils. The effects of wax on bitumen properties depend on the following factors: the source, chemical composition and rheology of the bitumen as well as the content, type, composition and crystallisation of the wax. There is a lack of literature reviews related to the effect of waxes on the rheology and properties of bitumen. The scope of this study is to evaluate the rheological properties of waxy bitumens obtained from different sources. Following the determination of wax contents by differential scanning calorimetry (DSC) and EN 12606-1, waxy bitumen properties were evaluated using conventional methods, rotational viscosity, dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests. The intermediate and high-temperature performances levels of bitumen were also determined according to the Superpave system by a DSR test performed on aged and unaged samples. Rutting performance of bitumens has been evaluated using zero shear viscosity (ZSV) and multiple stress creep recovery (MSCR) tests.

Organik Ilık Karışım Asfalt Katkı Maddesinin Bitümlü Karışımların Yaşlanma Özellikleri Üzerine Etkilerinin İncelenmesi

Son yillarda arastirmacilar, bitumlu sicak karisim asfaltin yerini alacak benzer veya tercihen daha yuksek performansli, uretim maliyetlerini azaltan, dogal kaynaklari koruyan, cevreye daha az zararli ve uygulamada daha verimli bitumlu karisimlar elde etme yolunda calismalar yurutmektedirler. Ilik karisim asfalt sistemlerinin kullanimi ile asfalt numunelerinin karistirma ve sikistirma derecelerinde fark edilebilir dusus gozlenmektedir. Uygulama sicakliklarindaki belirgin dususlerin, asfalt kaplamalarda meydana gelebilecek yaslanmadan kaynaklanan bozulmalari azaltacagi ongorulmektedir. Bu calismada, organik ilik karisim asfalt katki maddesinin bitumlu karisimlarin yaslanma ozellikleri uzerine etkileri arastirilmistir. Cesitli oranlarda organik ilik karisim asfalt katki maddesi iceren bitum ile hazirlanan asfalt karisimlari ve kontrol karisimlari; kisa donem ve uzun donem yaslanmaya tabi tutulduktan sonra yaslanma oranlari ve yaslanma indeksleri, indirekt cekme mukavemeti deneyleri ile belirlenmistir. Deney sonuclari, bitumlu sicak karisimlara kiyasla organik katki iceren ilik karisim asfalt numunelerinin yaslanmaya karsi daha direncli oldugunu gostermektedir. In recent years, researchers have been conducting studies in order to discover new alternative technologies for hot mix asphalts. These new technologies are expected to be higher in performance, lower in costs, sustainable over natural resources, environmentally friendly and easy to apply. With utilization of warm mix asphalt technologies, it is possible to decrease mixing and compaction temperatures of asphalt applications. In warm mix asphalt pavements, it is expected that ageing induced failures be less than hot mix asphalt pavements due to lower application temperatures. Within the scope of this study, the effects of an organic warm mix asphalt additive over ageing characteristics of bituminous mixtures have been investigated. In order to estimate the proportion of hardening of warm mix asphalt specimens containing different contents of organic additive and control specimens with no additive content, all specimens have been subjected to short- and long-term ageing. Afterwards, ageing indices have been calculated considering the ratio of indirect tensile strength values of both short- and long-term aged specimens over un-aged specimens. The results show that the aging indices of specimens containing organic warm mix asphalt additive are rather less than the indices of hot mix asphalt specimens. Anahtar kelimeler: Ilik karisim asfalt, Organik katki, Kisa donem yaslanma, Uzun donem yaslanma, Indirekt cekme mukavemeti.

Rheology and microstructure of polymer-modified asphalt nanocomposites

Abstract Asphalt modification with polymers has utilized the advantages of nanotechnology including nanoclays as one of the components in addition to polymers. This led to the metamorphosis of polymer-modified asphalts into a new class of material called polymer-modified asphalt nanocomposites which offer the cumulative characteristic features obtained by the polymer modification of asphalt as well as the innovative properties experienced from polymer nanocomposites. Polymer-modified asphalt nanocomposites including styrene butadiene and ethylene vinyl acetate have revealed additional features which were not available in polymer-modified asphalts. The compositional complexity provides a great challenge in addressing the structure–property relations prevailing in these materials. This paper describes microstructural features as determined by Qwin Plus Software analysis and the rheological properties on compositional changes.

Effect of polymers on rheological properties of waxy bitumens

DOI: 10.7764/RDLC.17.2.279 The definition of bitumen wax has been formulated to facilitate the distinction between harmful wax and less harmful or non-harmful. Since exact behaviour of waxes within bitumens is not completely determined and the absence of cooperative study related to modification of bitumens involving different amounts of waxes, the values found in the study are thought to be useful in determining which content of wax and type of polymer would be better for the needs of petroleum refineries in different countries. The scope of this study is to minimize the negative effects of waxes within bitumens obtained from different sources. For this purpose, modified bitumen samples were prepared by using different types of polymers such as elastomers, plastomers and polyethylene groups. Following the determination of the contents of wax by Differential Scanning Calorimetry and TS EN 12606-1, rheological properties of waxy bitumens and polymer modified bitumens (PMB) were evaluated using dynamic shear rheometer tests. The intermediate temperature performance levels of PMB were also determined by fatigue parameters. Besides, rutting performance of PMB was evaluated using Zero Shear Viscosity and Multiple Stress Creep Recovery tests.

Permanent deformation characteristics of warm mix asphalt

Warm Mix Asphalt (WMA) is a technology that allows lowering the production and paving temperature compared to Hot Mix Asphalt (HMA). The reduction of temperature enables various benefits over asphalt mixtures such as decreasing greenhouse gas emissions, lowering energy consumption, fuel cost saving, improved workability and easy compaction. Besides, WMA technology gives an option to use Recycled Asphalt Pavement (RAP) that provides a very economic method and eco-friendly pavements. The objective of this study was to evaluate the utilization of organic and chemical WMA additives with different percentages of RAP. Following the determination of optimum RAP contents corresponding to each WMA additive Hamburg Wheel Tracking Test is performed to obtain the permanent deformation characteristics of mixtures containing optimum RAP contents.