Geri kazanılmış asfalt betonunun bitümlü temel tabakasında kullanılabilirliğinin araştırılması
Investigation of the usability of recycled asphalt concrete material in the bituminous base course
Yazar: HANDE VAROL
Danışman: PROF. DR. ABDULLAH HİLMİ LAV
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Ulaştırma Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2019
Konu: Ulaşım = Transportation ; İnşaat Mühendisliği = Civil Engineering
Dizin: Bitümlü karışımlar = Bituminous mixtures ; Bitümlü sıcak karışım = Bituminous hot mixture

Özet:
Günümüzde sürdürülebilirlik, çevresel etkilerin en aza indirilmesi, maddi kaynak ve enerji tasarrufu gibi birçok faktör açısından mevcut kaynakların geri dönüştürülerek yeniden kullanılması gitgide önem kazanmaktadır. Herhangi bir alanda kullanım ömrünü tamamlamış olan atık malzemelerin birtakım işlemlerden geçerek üretim sürecine dahil edilmesine geri dönüşüm adı verilmektedir. Geri dönüşüm yöntemleri üstyapı bakım, onarım ve rehabilitasyonunda kullanılmaya başlanılmıştır. Hizmet ömrünü tamamlamış yol üstyapı kaplamasının geri dönüştürülerek yeniden kullanılması şeklindedir. 
Dünya genelinde gelişmiş ülkelerde çoktan kullanılmaya hatta geliştirilmeye başlanan geri dönüşüm uygulamalarına ülkemizde geç başlanmış olsa dahi birçok alanda uygulaması mevcuttur. Atıkların değerlendirilmesi için en etkili yol olan geri dönüşüm maliyet ve enerji tasarruflarına duyulan ihtiyaç ve artan atık yığınları sorunu gibi sebeplerden dolayı ilgi çekici olmaktadır. Cam, lastik, inşaat molozları ve cüruf gibi birçok atık malzemenin en etkin şekilde geri dönüşümde kullanım yerlerinden biri karayolu üstyapısıdır. Malzeme cinsine göre değişmekle birlikte genellikle temel tabakalarında agregalara katkı maddesi olarak kullanılmaktadırlar. 
Kazınmış asfalt kaplamalar da geri dönüştürülerek ya söküldükleri yol yüzeyinde tekrar ya da yeni bir yol üstyapısında katkı malzemesi veya ana malzeme olarak kullanılabilmektedir. Böylelikle hizmet ömrünü tamamlamış asfalt kaplamalar atık malzeme olmaktan çıkarak hem çevreyi kirletmemekte, hem de yeni malzeme kullanımının önüne geçerek doğal kaynakların korunumunu ve maliyetin azaltılmasına katkı sağlamaktadır.
Bu tez çalışmasında geri kazanılmış asfalt betonu malzemesinin (RAP) bitümlü temel tabakasında kullanılabilirliği araştırılmıştır. Belirli oranlarda RAP ilave edilen numunelerin akma, stabilite ve indirekt çekme mukavemetleri incelenmiştir. Çalışmada öncelikle ekstraksiyonla RAP malzemesi ayrıştırılmış, karışımı oluşturan bitüm ve agregaların fiziksel ve mekanik özellikleri çeşitli testlerle incelenmiştir. Marshall yöntemiyle bitümlü sıcak karışım dizaynı yapılarak optimum bitüm mikatrı belirlenmiştir. Belirlenen optimum bitüm miktarı içeriğinde hazırlanan asfalt betonu numunelerinin içine değişik oranlarda (%10, %20, %30, %40 ve %46) RAP ilave edilmiştir. Bunun yanında RAP ilave edilmemiş şahit numuneler de hazırlanmış, aynı testlere tabi tutularak sonuçlar karşılaştırılmıştır. Test sonuçları RAP ilave edilmiş bitümlü sıcak karışım numunelerinin stabilite, akma ve indirekt çekme mukavemeti yönünden Karayolları Teknik Şartnamesi'ndeki (KTŞ) sınırlar içerisinde olduğunu ve karayolu esnek üstyapıları bitümlü temel tabakasında kullanılabileceğini göstermiştir.

Abstract:
Today, it is becoming increasingly important to recycle and reuse existing resources in terms of sustainability, minimization of environmental impacts, financial resources and energy savings. In any field of use of end of life are given a number of recycling of waste material name to be included in the process of passing through the manufacturing process. The recycling method, which is widely used in maintenance and repair of highways, is in the form of recycling and reuse of road superstructure covering whose service life is completed.
Recycling applications, which have already started to be used or developed in developed countries around the world, have been implemented in many areas even though they have been started late in our country. Recycling is the most effective way to evaluate waste, and it is interesting for reasons such as the need for energy savings and increased waste stacks. One of the most efficient places for recycling of waste materials such as glass, tires, construction debris and slag is the highway superstructure. Although they vary according to the type of material, they are generally used as additives to the aggregates in their basic layers.
The engraved asphalt pavements can also be recycled or reused on the surface of the road where they are removed or used as additive or main material in a new road superstructure. Thus, asphalt pavements, which have completed their service life, do not pollute the environment and prevent the use of new materials and contribute to reducing the cost of natural resources.
In this thesis, the usability of recovered asphalt concrete material (RAP) in the bituminous base layer was investigated. Flow, stability and indirect tensile strengths of samples with RAP added in certain ratios were investigated. In the study, the RAP material was firstly separated by extraction and the physical and mechanical properties of the bitumen and aggregates forming the mixture were examined by various tests. The optimum bitumen amount for the bituminous base course was found by the Marshall method and then the same bitumen contents were added to the asphalt concrete samples prepared in optimum bitumen content (10%, 20%, 30%, 40% and 46%). In addition, no additional RAP samples were prepared and the same tests were performed and the results were compared. Test results showed that bituminous hot mix samples with RAP added were within the boundaries of the Highways Technical Specification in terms of stability, yield and indirect tensile strength, and that the highway flexible superstructures could be used in the bituminous base course.
In the first part of the study, the purpose of the thesis and the path followed are briefly explained and the literature research is included. In the literature research, it has been explained in which layers the RAP added mixtures are used in which layers are given. According to the investigations, RAP was mostly tested in the base layers and stabilized by adding in average 20-30% range.
The second part contains information about the highway superstructure. Road superstructure is flexible and rigid superstructure. Flexible pavements are formed by bituminous binders, while rigid pavements are formed by cementitious binders. In this section, information is given about the bituminous base layer of flexible pavements and flexible pavements. In the bituminous base layer, the desired limit values are explained according to the Highways Technical Specification. Bituminous hot mixtures consist of a mixture of bituminous binders and aggregates. Information about bitumen which is a hydrocarbon bond is given and the behaviors of the materials in aggregates are explained. Gravity, durability, grain shape and shape, porosity, surface texture and strengthening resistance of aggregates are explained.
In the material of the flexible pavements, the deterioration occurs due to the time period of the base floor, the load capacity, the traffic loads and the climate. These deteriorations occur in various conditions such as breakage, hollow, surface deformation or decomposition. Each type of deterioration is explained briefly and it is explained what should be understood from the degraded asphalt pavement.
In the third chapter, recycling methods applied on highways are explained. Recycling methods are grouped into five main headings: cold correction, hot recycling, on-site hot recycling, superficial recycling, cold recycling and full depth recycling. The method to be applied is determined by the traffic volume of the road. On roads with high traffic volume, mostly hot recycling method is applied. In this section, together with the recycling methods, the economic and environmental benefits of using RAP are explained and the practices in the world and in our country are shown as examples. The reuse of RAP in hot asphalt mixtures reduces the emission of most harmful gases, while the need for new material is reduced and the conservation of the natural environment is ensured. The use of new materials in the superstructure is more costly than using old materials. Thanks to recycling, the economy is also profitable.
In the fourth part of the study, the properties of the materials are explained and the experiments are explained. Bitumen and aggregates were first separated by applying extraction to the etched asphalt. Grading of the resulting aggregates by sieve analysis method was determined. The Los Angeles (wear) test was applied to the etched coating and the resulting coarse and fine aggregates with specific gravity test. Asphalt cement was subjected to penetration, softening point and specific gravity tests. Then the specified gradation for the bituminous base layer was determined in the Highways Technical Specification. The optimum bitumen amount of the mixture was determined by applying the Marshall method. New blends were formed by adding RAP at 0%, 10%, 20%, 30%, 40% and 46% to the mixture in such a way that the optimum bitumen amount remained constant. Marshall stability and indirect tensile strength test were applied to these new mixtures.
In the fifth chapter, the results of the experiments are given. The specific gravity applied to the aggregates and the penetration, softening point and specific gravity test results applied to the bitumen were compared with the specification values. The results of optimum bitumen amount are given and Marshall stability and indirect tensile strength test results applied to the mixtures prepared with optimum bitumen are shown. Stability, flow rate, air gap in the mixture, inter-aggregate space rate, asphalt filled space rate, indirect tensile strength and tensile strength ratios were evaluated and compared with the desired limit values in the Highways Technical Specification.
In the sixth and last part of the study, the results obtained from all experiments were briefly evaluated and shown. Recommendations are made for those who will use the RAP blended mixtures in the bituminous base layer. In the thesis study, it was observed that the addition of RAP to the hot asphalt mixtures showed some positive results and provided the Highways Technical Specification limit values.