Effects of Warm Mix Asphalt Additives on Aging Characteristics of Bituminous Mixtures

In recent decades, the utilization of the warm mix technologies in pavement constructions is increasing rapidly with rise in public environmental awareness. The durability of a pavement highly depend on the behavior of the pavement against aging induced failures. Therefore this study encompasses the evaluation of short- and long-term aging characteristics of four kinds of Warm Mix Asphalt (WMA) additives. Additives distinctly assessed in this study, consist of two non-foaming (organic and chemical) and two foaming(synthetic and natural zeolite) additives. In order to appraise the proportion of hardening of mixtures containing dierent kinds of additives, indirect tensile strength (ITS) values of both short- and long-term aged specimens were determined. Based on relative aging indices derived from the ratio of ITS values of aged and unaged specimens, comparisons were made between the additives assessing the impact of their utilization on aging characteristics of WMA

Cold War in Asia: China's Involvement in the Korean and Vietnam War

As essential components of the Cold War, the Korean War and the Vietnam War have played significant roles in global policy among the Western forces under the leadership of the United States and the Eastern bloc led by the Soviet Union in the 20th century. Communist China, founded in 1949, was also part of the countries behind the Iron Curtain and provided substantial support to North Korea and North Vietnam in their fight against their ideological enemies. Despite the extensive research by scholars on the Korean War and the Vietnam War, as well as China’s role in both of these wars, it is interesting to know whether China’s role and attitude had changed from one war to the other. This thesis examines and compares China’s military interference in the Korean War in the beginning of the 1950s with its involvement more than ten years later in the Vietnam War through the investigation of China’s motives to enter the wars and their ways of support in connection with the development of foreign relations. While contrasting China’s role and involvement in Korea and Vietnam, similarities, but also major differences become distinguishable. This thesis argues that these major differences indicate a Chinese rethinking about a possible involvement in Vietnam because of China’s domestic problems and its foreign policy developments at that time

Ilık karışım asfalt katkıların bitümlü karışımların yaşlanması üzerindeki etkileri

Günümüzde dünya genelinde Ilık Karışım Asfalt (IKA) teknolojisinin kullanımı hızla artmaktadır. Bu nedenle, IKA teknolojisinin belirlenmemiş bazı yönleri ve özelliklerinin ortaya çıkarılması gerekmektedir. Henüz bu alandaki uygulama ve araştırmalar yeni olduğundan, mevcut IKA katkılı kaplamaların pratikte uzun vadeli özelliklerini değerlendirmek henüz tam olarak mümkün olamamaktadır._x000B_Bu çalışma kapsamında, laboratuvarda kısa ve uzun dönem yaşlanma koşullarına tabi tutularak değişik içeriklerde dört farklı IKA katkılı karışım hazırlanmıştır. Bununla birlikte, hiçbir katkı maddesi içeriğine sahip olmayan numuneler de kontrol amaçlı hazırlanmıştır. Bu tezde değerlendirilen katkılar, Sasobit (organik katkı) ve Rediset WMX (kimyasal katkı) gibi granüler katkılar ile bunların yanında toz halinde olan Advera WMA ve doğal zeolit gibi köpüklendirme yöntemi içerisinde değerlendirilen katkılardır. Sertleşme oranlarının değerlendirilebilmesi için yaşlandırılmamış, kısa dönem yaşlandırılımış ve uzun dönem yaşlandırılmış farklı katkılar içeren IKA numuneleri üzerinde indirekt çekme deneyi uygulanmıştır. Kısa ve uzun dönem yaşlandırılmış numunelerin indirekt çekme mukavemeti (ITS) değerleri ile yaşlandırılmamış kontrol numunelerinin ITS değerleri arasındaki oran yaşlanma indeksi olarak hesaplanmıştır. Elde edilen yaşlanma indekslerine göre, dört farklı IKA katkısının, karışımdaki yaşlanma özellikleri üzerine etkisi değerlendirilmiştir. Her bir IKA katkısı için hesaplanan yaşlanma indeksi, o katkının kaplamanın servis ömrü boyunca, yaşlanmaya bağlı bozulmalara karşı gösterdiği davranış özelliklerinin belirlenmesinde yardımcı olmaktadır._x000B_Elde edilen sonuçlara göre, IKA katkılar ile hazırlanan karışımların yaşlanma indeksleri, sıcak karışım asfaltlara göre daha düşüktür. Tanımlanan yaşlanma indeksine göreceli bir değer olup, bitümlü karışımlardaki yaşlanma indeksi ne kadar düşük ise, yaşlanmaya karşı dayanımın o kadar yüksek olduğunu ifade eder. Kimyasal IKA katkısı olan Rediset WMX'in, diğer IKA katkılarla karşılaştırıldığında, en düşük yaşlanma indeksine sahip olduğu belirlenmiştir. Benzer açıdan, organik IKA katkısı olan Sasobit'in Rediset WMX ile yakın davranış gösterdiği tespit edilmiştir. Advera WMA ve doğal zeolit gibi köpüklendirme yöntemlerinin, yaşlanmaya karşı nisbeten daha az direnç gösterebildikleri belirlenmiştir. Since the utilization of Warm Mix Asphalt (WMA) technology is increasing rapidly around the world, it?s commonly believed that there are some unknown characteristics of this technology which should be investigated more sensibly. As most of the field practices of this technology have been applied recently, there is nearly no chance to evaluate long-term characteristics of existing WMA pavements practically._x000B_Within the scope of this study, short- and long-term aging conditions were applied to mixtures prepared with various contents of four different WMA additives as well as to control specimens with no additive content. WMA additives, which were distinctly assessed in this study, are Sasobit and Rediset WMX as non-foaming granular additives; moreover Advera and Natural Zeolite both in powder form as foaming additives, respectively. To estimate the proportion of hardening of WMA mixtures containing different types of additives, Indirect Tensile Strength (ITS) of both short- and long-term aged specimens were determined as well as of un-aged specimens. Based on relative aging indices (as the ratio of ITS results of aged specimens to ITS results of un-aged specimens), comparisons were made between four WMA additives to assess their effect on aging characteristics of mixtures. The defined Aging Index (AI) for each WMA additive can give us an evaluation capability to predict how a WMA pavement would be subjected to damages during service life of a pavement in comparison to a Hot Mix Asphalt (HMA) pavement._x000B_The results showed that aging indices for WMA technologies are rather less than the index for HMA mixture. The defined aging index is a relative parameter; the less aging index of a mixture is the better that mixture is in terms of aging characteristics. Rediset® WMX represented the least aging index. Sasobit performed nearly similar to Rediset WMX. Foaming additives including Advera and natural zeolite represented relatively weak aging strengths

Laboratory comparison of aging characteristics of warm mix asphalts involving natural and synthetic water containing additives

When comparing the aging characteristics of hot and warm mix asphalts from a technical point of view, it can intuitively be expected that a warm mix asphalt would be less subjected to aging-induced failures due to lower application temperatures. Since the side effects of warm asphalt technology should be investigated distinctly. This study addresses the aging investigation of properties of bituminous mixtures containing two (i.e., natural and synthetic zeolite) water based additives available on the market. Within the scope of this study, short- and long-term aging conditions were simulated on mixtures containing various contents of additives as well as on control specimens. The aging indices were determined based on the hardness ratio employing indirect tensile strength values in order to investigate the aging induced failures betide by time. Aging indices showed that the specimens with water containing additives demonstrate relatively better resistance against hardening than conventional hot mix asphalt specimens

Rheological and Microstructural Investigation of the Effects of Rejuvenators on Reclaimed Asphalt Pavement Bitumen by DSR and AFM

Utilization of RAP in asphalt pavements may lead to severe quality problems, mostly due to asphalt aging phenomenon. Within the scope of this study, the use of rejuvenators to improve the properties of RAP is investigated. Two different types of waste oils together with a commercial rejuvenator are used. The rejuvenated bitumen samples are evaluated from both rheological and microstructural aspects. In addition, mixture testing also employed to investigate the effectiveness of used rejuvenators. Experimental studies on bitumen samples included conventional and Dynamic Shear Rheometer (DSR) testing and Atomic Force Microscopy (AFM) imagings. The results unveiled that, the utilization of rejuvenators can significantly improve the quality of recycled asphalt and threatened the aged bitumen quality. Missing bee-structures of aged bitumen samples evolve in a different type of surface topography while the mixtures performance evolves in terms of workability. The rejuvenation process provides viscous behavior to aged bitumen. The Rejuvenation Index (RI) which is a dimensionless value, simply evolves this fact. While the RI of the non-rejuvenated aged bitumen is taken as 1 (one) as per RI definition, the neat bitumen RI is calculated as 0.79, the RI of waste oils are calculated as 0.74 and 0.79 while the commercial sample RI is calculated as 0.60. Among the rejuvenators, waste oils showed similar results with almost same volume of peri- and para-phase since the commercial rejuvenator behaved more similar to neat bitumen. The rejuvenated samples workability performance improves using rejuvenating additives. Binder and mixture testing demonstrated high consistency and conformity with each other in terms of performance and aging characteristics. The results proved that, waste oils can be used as rejuvenating agents within RAP. Rejuvenators can significantly restore the properties of aged RAP bitumen and increase the amount of RAP in bituminous mixtures

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

Son yıllarda araştırmacılar, bitümlü sıcak karışım asfaltın yerini alacak benzer veya tercihen daha yüksek performanslı, üretim maliyetlerini azaltan, doğal kaynakları koruyan, çevreye daha az zararlı ve uygulamada daha verimli bitümlü karışımlar elde etme yolunda çalışmalar yürütmektedirler. Ilık karışım asfalt sistemlerinin kullanımı ile asfalt numunelerinin karıştırma ve sıkıştırma derecelerinde fark edilebilir düşüş gözlenmektedir. Uygulama sıcaklıklarındaki belirgin düşüşlerin, asfalt kaplamalarda meydana gelebilecek yaşlanmadan kaynaklanan bozulmaları azaltacağı öngörülmektedir. Bu çalışmada, organik ılık karışım asfalt katkı maddesinin bitümlü karışımların yaşlanma özellikleri üzerine etkileri araştırılmıştır. Çeşitli oranlarda organik ılık karışım asfalt katkı maddesi içeren bitüm ile hazırlanan asfalt karışımları ve kontrol karışımları; kısa dönem ve uzun dönem yaşlanmaya tabi tutulduktan sonra yaşlanma oranları ve yaşlanma indeksleri, indirekt çekme mukavemeti deneyleri ile belirlenmiştir. Deney sonuçları, bitümlü sıcak karışımlara kıyasla organik katkı içeren ılık karışım asfalt numunelerinin yaşlanmaya karşı daha dirençli olduğunu göstermektedir