Gama ışınları ile yaşlandırılmış bitüm ve bitümlü karışımların reolojik incelenmesi
Rheological investigation of bitumen and bituminous mixtures aged with gamma rays
Yazar: MERVE CEYHAN ERDOĞAN
Danışman: PROF. DR. ABDULLAH HİLMİ LAV
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Ulaştırma Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2020
Konu: Ulaşım = Transportation

Özet:
Esnek üstyapılarda meydana gelen yaşlanmalar, kısa dönemli yaşlanmalar ve uzun dönemli yaşlanmalar olarak iki kısıma ayrılmıştır. Kısa dönemli yaşlanmalar TFOT, RTFOT ve uzun dönemli yaşlanmalar PAV ile laboratuvar ortamlarında oluşturulmaya çalışılmış ancak güneş ışınlarından dolayı asfalt çimetosunda meydana gelen bozulmalar ve yaşlanmalar için yeterli olmamıştır. Asfalt çimentosunda meydana gelen yaşlanmalar agrega ile olan aderansın kaybolmasına ve yol yüzeyinde zamanla çeşitli deformasyonlara sebep olmaktadır. Asfalt çimentosuna bağlı bozulmalar genellikle aşınma tabakasında oluşur. Daha aşağıdaki tabakalarda deformasyon olmamasına rağmen koruyucu tabakadaki bozulmalardan alttaki tabakalar da iklimsel oluşumlardan zamanla etkilenirler.
Bu çalışmada asfalt çimentolarında güneş ışınlarından dolayı meydana gelecek yaşlanma gama ışını kullanılarak oluşturulmuş ve asfalt çimentosundaki performans kaybı gözlemlenmiştir. Çalışmada laboratuvar ortamında 40-50, 50-70 ve 70-100 penetrasyonlu saf asfalt çimentosu kullanılmıştır. Çalışmada üç farklı bitüm çeşidi ile %4, %4,5 ve %5 bitüm oranına sahip aşınma tabakası marshall numuneleri üretilmiştir. Daha sonra elde edilen numuneler referans numuneleri ve ışınlamaya tabi tutulacak numuneler olmak üzere gruplandırılmıştır. Numuneler GammaPak A.Ş. tesislerinde 50 kGy, 150 kGy ve 250 kGy dozlarında ışınlanmıştır. Hem ışınlamaya tabi tutulan hem de referans marshall numuneleri için kullanılan bitüm, ekstraktör ve döner buharlaştırıcı ile geri kazanılmıştır. Geri kazanım için trikloretilen çözücü ile soksilet ekstraktör ve döner buharlaştırıcı (rotary evaporator) kullanılmıştır. Marshall briketlerinden geri kazanımı yapılan numuneler üzerinde penetrasyon, yumuşama noktası ve DSR deneyleri yapılmıştır. Ayrıca saf bitüm numuneleri de ışınlamaya tabi tutulmuştur ve bu numuneler için de aynı deneyler tekrarlanmıştır. Böylece hem aşınma tabakası üzerinde gama ışınına bağlı oluşacak yaşlanma hem de asfalt çimentosu üzerindeki yaşlanma verileri elde edilmiştir. Asfalt çimentosuna ait deney sonuçları, ışınlanmış asfalt çimentosuna ait deney sonuçları, farklı oranlarda bitüm kullanılarak üretilen referans marshall numunelerinden geri kazanımla elde edilen asfalt çimentosuna ait deney sonuçları, ışınlanmış marshall numunelerinden geri kazanımla elde edilen asfalt çimentosuna ait deney sonuçları için karşılaştırma yapılmıştır. Karşılaştırma sonucunda her üç asfalt çimentosu türü için gama ışın dozu artırıldığında reolojik özelliklerinin belli oranlarda kaybedildiği sonucuna ulaşılmıştır. Ayrıca güneş ışınları ile yaşlanan esnek üstyapılarda asfalt çimentosu film kalınlığının etkisini ölçmek için üretilen %4, %4,5 ve %5 AC karışımlı marshall numunelerinde aynı doz ışına maruz kalan numunelerde %4 oranlı olan karışımda yaşlanma etkilerinin daha fazla görüldüğü, bunun sebebinin de karışım agregasını saran asfalt çimentosu film kalınlığının daha ince olması sonucuna varılmıştır.

Abstract:
Investments in the transportation sector and transportation, as well as maintenance and repair investments, have an important place. Highway pavements are generally examined in two parts as flexible and rigid pavements and construction, maintenance and repairs of flexible pavements made up of bituminous mixtures in our country have more place than rigid pavements. 
Flexible pavements are structures consisting of a bituminous protective layer (wearing, binder) at the top, a base consisting of bituminous or granular material underneath, and a granular base layer at the bottom. Since the wearing layer is the top layer, it is the part where the aging effects and the related deformations are seen with the effects such as sun rays, temperature, oxygen, traffic etc. Therefore, it is the most common layer of maintenance and repair work. Therefore, the studies conducted to minimize the effects of aging are mostly concentrated on this layer.
The change in the rheological properties of bituminous binders / mixtures is due to changes in chemical compositions occurring during the production, construction and service period. Examination of aging effects in bituminous binders / mixtures has an important place. The aging of asphalt binders causes the asphalt mechanical performance to be affected due to changes in their rheological behavior and binder composition. Aging causes the asphalt to harden due to the oxidation of the asphalt binder itself.
Aging in flexible pavements is divided into two parts as short-term aging and long-term aging. Short-term aging and long-term aging have been tried to be established with RTFOT (Rolling Thin Film Oven Test) and PAV (Pressure Aging Vessel) in laboratory environment, but due to sun rays deterioration on asphalt cement, these tests were not enough for aging. 
Aging in asphalt cement causes loss of adherence with aggregate and various deformations on the road surface over time. Deterioration in asphalt cement usually occurs in the wear layer. Although there is no deformation in the lower layers, the lower layers are also affected by climatic formations over time. 
In this study, aging of the asphalt cements due to sun rays was formed by using different doses of gamma rays and performance loss was observed in asphalt cements. Pure bitumen with 40-50, 50-70 and 70-100 penetration values were used in the laboratory. Also, three different types of bitumen and %4, 4,5% and 5% bitumen rate marshall samples were produced. The reason for experimenting with bituminous mixtures is to investigate the effects of asphalt cement film thickness on aging. The expected result in this study is that the aging effects are more common in samples with thinner film thickness.
The samples obtained were then grouped as reference samples and samples to be irradiated. Pure asphalt cements which have penetration degree 40-50, 50-70 and 70-100 and the other group 4%, 4,5% and 5% AC mixture marshall samples were irradiated in GammaPak AŞ facility by 50 kGy, 150 kGy and 250 kGy. The irradiated Marshall samples and pure asphalt cements were brought to the laboratory for later experimentation. Asphalt cement was recovered from both irradiated Marshall samples and non-irradiated Marshall samples. Asphalt cement obtained from non-irradiated samples is accepted as reference sample for others. Then asphalt cement was recovered from all marshall samples. The process of recovering asphalt cement was carried out in two stages. In the first stage, the samples were dissolved in soxhlet extractor with ethylene and in the second stage, asphalt cement was separated from ethylene with rotary evaporator. 
Penetration, softening point and DSR tests were performed on the samples recovered from Marshall briquettes. Pure bitumen samples were also irradiated, and the same experiments were repeated for these samples. Thus, both the aging data due to gamma radiation on the wearing course and the aging data on asphalt cement were obtained. 
Test results of pure asphalt cement, test results of irradiated pure asphalt cement, test results of asphalt cement obtained by recovery from reference marshall samples produced by using different ratios of bitumen, test results of bitumen obtained by recovery from irradiated marshall samples were compared. As a result of comparison, it was concluded that rheological properties were lost when gamma ray dose was increased for all three bitumen types. 
In addition, in order to measure the effect of asphalt cement film thickness on flexible pavements aging by sunrays, 4%, 4,5% and 5% AC mixture marshall samples were produced and irradiated then aging effects were seen more in 4% compared with 4,5% and 5% AC mixture marshall samples.
As a result of the experiments, it is concluded that rutting parameter decreases (G * / sinδ) and the phase angle (δ) increases in the samples exposed to gamma ray despite the formation of traces. In addition, it has been observed that the penetration increases and the softening point decreases with the decrease of the rutting parameter. Another result is that the rutting parameters of the recycled AC samples higher than the non-recycled samples. In the samples obtained with recovery, a decrease in penetration value and an increase in softening point were also observed according to their references. While samples that received 50 kGy dose in relatively pure irradiated samples showed relatively less variation, samples with 150 and 250 kGy doses were excluded from the specification limits and their rheological properties were lost. 
Aging experiments are carried out to observe the effects of temperature, pressure etc. in aging bitumen and bituminous mixtures, but aging caused by sun rays is ignored. Although it is studied in the literature on the aging of UV rays and bitumen and bituminous mixtures, it takes much less place than other methods and it takes time to fully reflect the long-term aging. If the findings obtained from the study are done by repeating the same method with UV, then, if an equivalent dose is found, aging can be achieved in a much shorter time with the gamma ray. For this reason, this thesis will shed light on the aging studies due to future sun rays.
This thesis study consists of six chapters. In the first part of the thesis, the purpose of the study and the path followed are summarized and a literature review is included. In the second part, general information about highway pavement is given and only the wearing layer is mentioned from the pavement layers. Also, in this section, topics such as bituminous mixtures, rheological structure and aging of the bitumen are included. In the third section, material and method are discussed. The properties of the materials used in the material section are explained, the production stages, the irradiation process and the experiments of the applied methods are described in the method section. Experimental findings obtained in the fourth section are presented. In the fifth chapter, which is the last part of the thesis study, the results obtained from the study conducted are discussed and suggestions are included.