Polipropilen Liflerin Uçucu Kül Zemin Karışımlarında Geoteknik Özelliklere Etkisi

Abstract

Termik santrallerde kömürün yakılması sonucu ortaya çıkan ve endüstriyel bir atık olan uçucu kül, gelişmiş ülkelerde gerek çimentoyla karıştırılarak beton üretiminde, gerekse zemin içerisine katılarak stabilizasyon malzemesi olarak kullanılmaktadır. Böylece uçucu külle hem ekonomik bir fayda sağlanmakta hem de malzemenin depolanmasından veya bertaraf edilmesinden kaynaklanan çevre etkileri azaltılmaktadır. Fakat Türkiye’de ortaya çıkan uçucu kül miktarı oldukça fazla olmasına rağmen çok az bir miktarı tekrardan kullanılarak ekonomiye yeniden kazandırılmaktadır. Bu tez çalışmasında Zonguldak Çatalağzı Termik Santralinden alınmış F tipi uçucu kül ile Filyos Ateş Tuğla Fabrikasından alınmış yüksek plastisiteli bağlama kilinin eşit miktarda karıştırılmasıyla elde edilen karışım numunesi içerisine farklı oranlarda 19 mm uzunluğunda fibrilli (F tipi) polipropilen lif katılarak zayıf zeminlerin mühendislik özelliklerinin uçucu kül ve fiber katkısı yardımıyla iyileştirilmesi konusu yapılan laboratuvar deneyleriyle araştırılmıştır. İstanbul Teknik Üniversitesi Ord. Prof. Dr. Hamdi Peynircioğlu Zemin Mekaniği Laboratuvarı’nda yapılan deneylerde üç farklı tip malzeme kullanılmıştır. Kullanılan malzemeler; kil, uçucu kül ve polipropilen lif malzemesidir. Çalışmalarda kil ve uçucu külün elek analizi, hidrometre deneyi, kıvam limitleri, piknometre ve standart proktor deneyleri yapılmıştır. Bunlara ek olarak uçucu kül ile kil numunesinin eşit miktarda, ağırlıkça %50 oranında, karıştırılması ile oluşturulan kil-uçucu kül karışımı içerisine polipropilen lif sırasıyla karışımın ağırlıkça % 0.5, %1.0, % 1.5 ve % 2.0’si oranında karıştırılmıştır. Değişik oranlardaki karışım numunelerinde standart proktor, serbest basınç ve CBR deneyleri yapılarak deney sonuçları karşılaştırmalı olarak verilmiştir. Laboratuvar deneylerine ilave olarak uçucu külün kimyasal analiz sonuçları ile deneylerde kullanılan polipropilen lif malzemenin fiziksel özellikleri de tez kapsamında sunulmuştur. Yapılan deneysel çalışmalarda zayıf zemine uçucu kül ve fiber malzeme katılarak zemin iyileştirme yöntemi uygulandığında, fiberli kil-uçucu kül karışım malzemesinin CBR ve serbest basınç değerlerinde önemli oranda artış olduğu tespit edilmiş ve eşit miktarda malzemeyle hazırlanan kil-uçucu kül karışımı için en uygun fiber katkı oranı karışımın ağırlıkça %1.0’i olarak belirlenmiştir. Çalışmanın sonucunda yapılan laboratuvar deney sonuçlarına bakıldığında; kil-uçucu kül karışımının ağırlıkça %1.0’i oranında fiber katkısıyla hazırlanan fiberli kil-uçucu kül karışımında yapılan laboratuvar deney sonuçları fibersiz kil-uçucu kül karışımının değerleriyle karşılaştırıldığında, fiberli kil-uçucu kül karışımının CBR değerinin %100, serbest basınç değerinin ise %48 artış gösterdiği görülmüştür. % 1.0 fiber katkılı kil-uçucu kül karışımının CBR ve serbest basınç değerleri kilin yalın haldeki değerleriyle karşılaştırıldığında; fiberli karışımın CBR değerinin %500, serbest basınç değerinin ise %108 artış gösterdiği görülmüştür. Çalışmayla birlikte termik santrallerde yan ürün olarak ortaya çıkan, endüstriyel bir atık olan, su ve havayı kirleterek çevre kirliliğine neden olan uçucu külün sadece çimento ve beton endüstrisi gibi kısıtlı kullanım alanının olmadığı, zayıf zeminler üzerinde yapılması planlanan büyük kapsamlı projelerin yapılacağı büyük alanlardaki zayıf zeminlerin stabilizasyonlarında ya da yol dolguları gibi geoteknik uygulamalarda kullanılarak ekonomiye tekrar kazandırılması üzerine bir çalışma yapılmıştır. Çalışmada Zonguldak Çatalağzı Termik Santrali’nden çıkan uçucu küllerin santrale 15 km. mesafede bulunan ve GAP’tan sonra Türkiye’de gerçekleştirilecek en büyük entegre yatırımlardan biri olan Filyos Vadisi Projesi kapsamında yapılacak endüstri tesislerinin yapılacağı alanların ve bağlantı yollarının zemin iyileştirme çalışmalarında kullanılması tavsiye edilmektedir. Uçucu kül malzemenin endüstriyel bir atık olması, polipropilen lif malzemenin maliyetlerinin düşük olması nedeniyle tezin konusu olan uygulamanın pratikte gerçekleştirilmesinin önünde herhangi bir engel görülmemektedir. Zayıf zeminlere uçucu kül ve fiber katkısı yapılmasıyla ekonomik anlamda sağlanacak avantajların yanında uygulamanın çevreye duyarlı olması sebebiyle de ülkemize önemli faydalar sağlanacağı düşünülmektedir.

The thermal power plants generate significantly large quantities of solid byproduct namely fly ash. At present, the disposal of generated fly ash is by either wet disposal or dry disposal. Fly ash is also extensively used for a variety of construction materials in the world however only 10% of fly ash are being used in Turkey. Therefore, there is a need to address the problems encountered during the disposal or reuse fly ash in construction industry. Fly ash is produced as a result of coal combustion in thermal power plants. Fly ash defined as a heterogeneous mixture and is generally fine powdered material. Civil engineering projects located in areas with soft or weak soils have traditionally incorporated improvement of soil properties by using cement and lime. Use of fly ash as a ground improvement soil admixture, when found viable, will be effective in terms of cost and a good approach to the environment to preserve and minimize accumulation of industrial waste. This study is performed to obtain geotechnical properties of fly ash for its application in the stabilization of soft soil with the fiber. The geotechnical properties of clay, fly ash and fiber mixture will be evaluated with various laboratory tests to investigate the feasibility of using fly ash and fiber in soft soil stabilization. Constructions over soft soil are one of the most frequent problems in many parts of the world. The typical approach to soil stabilization is to remove the soft soil, and substitute it with a stronger material like crushed rock or apply other alternative soil improvement methods. Due to substantial cost of replacement, alternative methods to the problems are assessed. The study of using fly ash is carried out to observe the effectiveness of its addition on stabilization of soft soil. This is one of the approaches to overcome the increasing amount of solid waste generated by the population. A practical solution to the disposal problems would be the reuse of fly ash for civil engineering applications. The objectives of the study are to determine the geotechnical properties of fly ash and to investigate the effects of fly ash and fiber addition on the strength of stabilized soft soil. Scope of this study is to analyze the consequences of the application of fly ash and fiber in soft soil stabilization. It covers methods for determining the geotechnical properties of reinforced soil-fly ash mixture to assess its suitability for soft soil stabilization. The fly ash is taken from Çatalağzı Thermal Plant, Zonguldak, Turkey. Coal burning electric utilities annually produce million tons of fly ash as a waste byproduct and the environmentally acceptable disposal of this material has become an increasing concern. Efforts have always been made by the researchers to make pertinent use of fly ash in road constructions in the localities which exists in the vicinity of thermal power stations. Quality construction materials are not readily available in many locations and are costly to transport over long distance. Hence, over the last few years, environmental and economic issues have stimulated interest in development of alternative materials that can fulfill design specifications. The established techniques of soil-fly ash stabilization by adding cement, lime and reinforcement in form of fibers cause significant modification and improvement in engineering behavior of soil - fly ash. Fibers are simply added and mixed randomly with soil and fly ash. One of the most promising approaches in this area is use of fly ash as a replacement to the conventional weak earth material and fiber as reinforcement will solve two problems with one effort i.e. elimination of solid waste problem on one hand and provision of a needed construction material on other hand. Also, this will help in achieving sustainable development of natural resources. Soil used in the soil- fly ash mixtures was clay. The clay is taken from Filyos Firebricks Plant. The grain size distribution curve indicated that soil was primarily fine grained with approximately 42-47% silt size, 4-9% sand and 48-49% clay size particles. The specific gravity of soil solids was 2.681. The clay is classified as CH type in accordance with USCS, A-7 in accordance with AASHTO standards. Fresh fly ash samples were collected from Catalagzı Thermal Power Station, Zonguldak, Turkey. The fly ash is classified as Class F as per ASTM C618 (ASTM1993). The polypropylene fibers were provided by FiberForce Company. The polypropylene fibers used in the thesis were F19 type. Polypropylene fibers are %100 virgin polymer fiber, fibrillated form, non-crimped, contain no polyamide or no recycled materials, net shaped and rectangular. Laboratory tests were conducted at İstanbul Technical University Ord. Prof. Dr. Hamdi Peynircioğlu Soil Mechanics Laboratory. Sieve analysis, hydrometer analysis, pycnometer test, Atterberg limits, Standard Proctor, California Bearing Ratio, unconfined compression strength tests are conducted on the mixtures and plain materials and compared with each other. Observations from standard proctor tests, unconfined compression tests and California bearing ratio tests have been analyzed to study the effect of polypropylene fibers on engineering behavior of soil - fly ash mixtures. Standard Proctor tests were carried out on unreinforced and reinforced soil-fly ash mixes. In the case of soil- fly ash – fiber mixture, the moisture density relationship obtained from standard proctor tests showed that increasing fiber content from 0.00 % to 2.00 % by dry weight of soil mixed with fly ash had an effect on the magnitude of maximum dry density (MDD). MDD of soil-fly ash mixture decreases with addition of the fiber. Soil-fly ash-fiber mixture reaches highest MDD at 1.00% fiber level and it starts decrease after 1.00% of fiber. Standard proctor test indicated that variation in optimum moisture content (OMC) with no noticeable change as a function of increasing fiber content was between 16% to 18 %; with slight noticeable change in MDD of mixture at 1.00% of fiber. The effect of fiber inclusion on the unconfined compressive strength (UCS) and stress –strain relationship of soil-fly ash specimens was determined as a function of fiber content. Primarily, the tests were performed on unreinforced soil-fly ash to establish base UCS so that relative gain in UCS due to addition of polypropylene fibers could be estimated. Soil-fly ash-fiber mixture reaches highest UCS at 1.00% fiber level and it starts decrease after 1.00% of fiber. The results show that UCS of reinforced soil-fly ash increases 48% at 1.00% fiber level compared to unreinforced soil-fly ash mixture. In addition to that UCS of reinforced soil-fly ash mixture at 1.00% fiber level, increased 108% compared to plain clay. The CBR values for different soil-fly ash and polypropylene fiber mixture have been determined in the laboratory. The values of CBR for plain and reinforced soil- fly ash mixtures with varying percentages of polypropylene fibers are determined. Soil-fly ash-fiber mixture reaches highest CBR value at 1.00% fiber level and it starts decrease after 1.00% fiber. The results show that CBR value of reinforced soil-fly ash mixture increases 100% at 1.00% fiber level compared to unreinforced soil-fly ash mixture. In addition to that at 1.00% fiber level, CBR value of reinforced soil-fly ash mixture at 1.00% fiber level increased 500% compared to plain clay. The inclusion of fibers had a significant influence on the engineering behavior of soil-fly ash mixtures. The following are the major conclusions of this study on the engineering behavior of fiber reinforced soil-fly ash mixtures; • The moisture –density relationship of soil-fly ash -fiber mixtures had no major significant change due to addition of fibers. The MDD decreases and OMC increases in soil- fly ash-fiber mixtures compared to the unreinforced soil-fly ash mixture. • Inclusion of fibers increased the peak compressive strength of soil-fly ash specimens. Increase in fiber content improves the contribution of fibers to peak compressive strength up to 1.00% of fiber by dry weight. • The relative benefit in CBR values due to fiber inclusion increases only up to 1.00 % by dry weight. Soil-fly ash-fiber mixture reaches the highest CBR value at 1.00% of fiber by dry weight. • The results of thesis of a randomly oriented fiber reinforced soil- fly ash mixtures indicted that a maximum performance was achieved in optimum dosage of 1.00 % by dry weight of soil- fly ash mixtures with 19 mm fibers. CBR value of the reinforced soil-fly ash mixture with 1.00% inclusion of fiber increased 100%, UCS value increased 48% compared to unreinforced soil-fly ash mixture. CBR value of the reinforced soil-fly ash mixture with 1.00% inclusion of fiber increased 500%, UCS value increased 108% compared to plain clay material. The results indicate that F type Catalagzi fly ash and F19 type polypropylene fiber inclusion to soft soils can be used for soil stabilization. Due to distance and transportation problems, fly ash and fiber inclusion method to soft soils can be used on road construction and large embankment areas on the vicinity of the power plant. Therefore the method can be applied on Filyos Valley Project which is approximately 15 km to Catalagzi thermal power plant. Filyos Valley Project is one of the biggest integrated project of Turkey which covers more than 10 million square meter area, includes 25 million ton/year capacity port, industrial plants, industrial parks, free trade zones etc. Elimination of solid waste problem and provision of construction material for soil stabilization problems can be solved with this application. Also, this will help in achieving sustainable development of natural resources.