Polipropilen fiber liflerin asfalt betonunun eğilme dayanımı üzerindeki etkisinin araştırılması
Investigation of the effect of polypropylene polypropylene fibers on the strength of the asphalt concrete
Yazar: OĞUZHAN AKAR
Danışman: DOÇ. DR. MURAT ERGÜN
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

Özet:
Bu çalışmada son zamanlarda beton sanayisine kendini kabul ettirmiş çatlakların önlenmesi ve enerji sünme kapasitesinin artırılması açısından en önemli katkı malzemesi olarak görülen makrosentetik fiber liflerin, asfalt betonunda özellikle eğilme dayanımı ve enerji sönümleme kapasitesini ne boyutta etkileyeceği araştırılmış ve bu polimer malzemenin asfalt betonunda kullanımı tartışılmıştır.
Toplamda 6 bölümden oluşan bu çalışmanın ilk bölümünde  yapılan çalışmanın amacı ve izlenecek yol anahatları ile verilmeye çalışılmış ve tezin ana öğesi olan polipropilen lif ile ilgili literatürde yer alan çalışmalardan bahsedilmiştir.
İkinci bölüm, genel olarak yol üst yapısında kullanılan kaplama türleri, biribirilerine olan avantaj ve dezavantajları  ve bitümlü sıcak karışımların performans özellikleri ile ilgili geniş bilgileri içermektedir.
Polimer endüstrisi ve bu endüstrinin bir parçası olan polipropilen lifler, fiziksel ve kimyasal özellikleri, başlıca kullanım alanları üçüncü bölümün temel içeriğini oluşturmaktadır.
Dördüncü bölümde, deneysel çalışmalarda çeşitli kurumlardan temin edilen malzemelerle ilgili bilgi verilmiş, bu malzemelere gerekli deneyler uygulanmış ve elde edilen sonuçlar KTŞ 2013 ile karşılaştırılmıştır. Yapılan deneysel çalışmalarda ilk olarak Çiftalan Taşocağından temin edilen kırmataş agrega ve Enfalt A.Ş .den temin edilen bitüm üzerinde fiziksel özelliklerini belirlemeye yönelik deneyler yapılmıştır. Temin edilen agregalar üzerinde "Elek analizi, Özgül ağırlık ve su emme, Kil topağı ve dağılabilen dane oranı, Yassılık indeksi, Los Angeles ve Soyulma mukavemeti", bağlayı üzerinde ise "Penetrasyon, Düktilite, Yumuşama noktası ve Özgül ağırlık" deneyleri gerçekleştirilmiştir. Fiziksel özellikler belirlendikten sonra Marshall tasarımı yapılarak  %0,5 artışlarla değişen %3,0 ile %6,5 arasında bitüm içeriğine sahip 8 farklı karışım hazırlanarak "yoğunluk-boşluk" analizleri yapılmış, "stabilite-akma" değerleri ölçülmüştür. Elde edilen sonuçlara ilişkin grafikler çizilerek optimum bitüm  şartname limitlerine göre optimum değerlere ilişkin bitüm içerikleri belirlenmiştir. Çeşitli parametreleri optimum değerde tutan bitüm muhtevası % 4,7 olarak hesaplanmıştır. Marshal stabilite deneylerinden sonra üç noktalı eğilme deneyleri için farklı oranlarda  katkılı ve katkısız 7x7x28 boyutlarında asfalt kiriş numuneleri üretilmiştir. Üretilen numuneler üzerinde üç noktalı eğilme deneyleri uygulanmış katkılı ve katkısız numuneler için eğilme dayanımları hesaplanmıştır.
Son aşamada, elde edilen deney sonuçları sonuçları ve varılan kanaatler sunulmuştur. Makrosentetik fiber liflerin esnek yol üst yapısında kullanımı değerlendirilmiş ve ileride yapılabilecek çalışmalar için öneriler belirtilmiştir.

Abstract:
Road pavements in the countries are manufactured in three ways as concrete road pavement, flexible pavement and composite pavement. In general, most of the roads are manufactured as flexible road pavements. Flexible road pavements are a type of superstructure that is manufactured as a bituminous hot mixture and provides a comfortable and safe rolling surface to the vehicle to be traced. The performance of bituminous hot mixtures is evaluated by the ability to provide parameters such as "Stability, Rigidity, Slip and Fatigue Resistance, Impermeability, Durability, Flexibility and Workability".
Polymers are high molecular weight compounds which are formed by the reaction of chemical particles called monomers in a chain structure. Polymers have an important place in human life by replacing many natural and artificial materials due to their different material structures and different superior properties. Polymers used in the civil engineering and construction industry now constitute as important as 30% of the polymers produced in the world. Polypropylene fibers are a derivative of petroleum and because of their physical and chemical properties, it is an organic material which is widely used in the construction industry. It is widely used all over the world with inorganic binders such as cement and gypsum, and micro-binders such as bitumen, to enhance microstructures and to improve their durability. Also polypropylene fibers are distributed in different directions in concrete and assume the function of secondary reinforcement.
The reinforcement effect of polypropylene fibers in the asphalt concrete pavement can be explained as follows: Pressure stresses occur on the pavement surface due to the axle loads acting on the pavement. These compressive stresses cause the aggregates to move within the coating and consequently the formation of indirect tensile stresses. PP fibers added to the mixture are high rigidity and tensile strength. These fibers, which are randomly dispersed in the mixture, have high thermoplastic properties even when they melt at high temperatures and show their high mechanical properties when they are cooled and show the effect of secondary reinforcement by providing resistance against indirect tensile stresses occurring in the coating.
Beam bending test; is a test method used to determine the bending strength of generally beams with rectangular or circular cross-sections. According to TS 205, a deforming is defined when a bending force is applied to the center of a flat piece of material with a circular or rectangular cross section that is freely fitted to the two supports. The main reason of fatigue cracks in bituminous hot mixtures is that the indirect tensile and bending stresses caused by axle loads cause plastic deformations in the material. From this point of view, increasing the flexural strength of the mixture will increase the fatigue life of the coating.
In recent years, the increase in the volume of heavy tonnage traffic with the developing industry, flexible road pavement has resulted in various deterioration and frequent maintenance before the service life is completed. Therefore, researchers working on road pavements have been doing various studies to increase the flexible road performance characteristics. Modifying the bituminous hot mix with various materials is one of the most commonly used methods.
Modification of the asphalt binder or hot mixture with polymer has been shown to increase the resistance of the coating to corrugations, low heat cracks, fatigue cracks, peeling and temperature effects. Today, the use of modified asphalt has become inevitable, especially on roads such as highway pavements, climbing lanes, airports, speedways that are subjected to heavy tonnage loads.
Within the scope of this study, it has been investigated how the macrosynthetic fibers, which are considered as the most important additive material in terms of preventing cracking and increasing the creep capacity of the concrete industry, will affect the bending strength and energy damping capacity in asphalt concrete and the usage of this polymer material in asphalt concrete is discussed.
In the first part of this study, which is composed of 6 chapters, the aim of the study and the outline of the path to be followed are tried to be given and the studies on the polypropylene fiber which is the main element of the thesis are mentioned.
The second part covers the wide range of coating types used in the road superstructure, the advantages and disadvantages to one of them and the performance properties of bituminous hot mixtures.
In the third section, the main material of this study, polypropylene fibers and polymer industry information is given. In this section, polymers used for the modification of asphalt concrete are classified and physical and chemical properties of polypropylene fibers are explained. In addition, the reinforcement effect of polypropylene fibers in asphalt concrete is explained and supported by figures. Finally, the section has been concluded by mentioning the usage areas of this material in different sectors.
In the fourth chapter, the information about the materials obtained from various institutions are given in the experimental studies, the necessary experiments are applied to these materials and the results are compared with the KTŞ 2013. In the experimental studies, firstly experiments were carried out to determine the physical properties of the crushed stone aggregate obtained from Çiftalan Quarry and the bitumen obtained from Enfalt A.Ş. "Sieve analysis, Specific gravity and water absorption, Clay pellet and dispersible grain ratio, Flatness index, Los Angeles and Peel strength" and "Penetration, Ductility, Softening point and Specific gravity" tests were performed on the aggregates obtained. After the physical properties were determined, "density-gap "analyzes were performed by preparing 8 different mixtures with bitumen content ranging from 3.0% to 6.5% in 0.5% increments by Marshall design and" stability-yield "values were measured. The graphs of the obtained results were shown and the bitumen contents of the optimum values were determined according to optimum bitumen specification limits. Bitumen content, which keeps various parameters at optimum value, was calculated as 4.7%. After Marshal stability tests, asphalt beam samples of 7x7x28 dimensions with and without additives were produced for three-point bending tests. Three-point bending tests were performed on the produced samples.
In the last stage, the results of the experiments and the conclusions reached are presented. The use of polypropylene fibers in the flexible path superstructure has been evaluated and recommendations have been made for future studies.