Beton Gürültü Bariyerleri İçin Ses Yutucu Perlit Esaslı Kaplama Tasarımı Yapılarak Fiziksel Performansının Ve Maliyetinin Araştırılması

Abstract

Bu tez çalışmasında; karayolu trafiği kaynaklı çevresel gürültü ile mücadele yöntemlerinden biri olan gürültü bariyerlerinde ses yutuculuğun arttırılması amacı ile özellikle beton bariyerler üzerinde uygulanabilecek olan perlit esaslı bir kaplamanın tasarlanması, fiziksel ve akustik özelliklerinin deneysel olarak belirlenmesi ve maliyetleri açısından değerlendirilmesi yapılmaktadır. Önerilen kaplama, Türkiye’de önemli miktarda rezervi bulunan perlitin sanayide yaygın kullanım şekli olan patlatılmış formunun 1200°C gibi yüksek bir sıcaklıkta belirli bir süre ile bekletilerek camsılaştırılması ile elde edilmektedir. Bu ısıl işlem sürecinde patlamış perlit parçacıkları aralarında boşluklar kalacak şekilde birbine kenetlenmekte ve büzülerek hacim kaybetmekte, soğutulduktan sonra ile gözenekli narin bir yapı oluşmaktadır. Patlatılmış perlitin bu işlemler sonrasındaki gözenekli yapısı, akustik ses yutuculuğa sahip birçok ürün ile benzer bir yapıda olduğundan, bu kaplamanın ses yutucu malzeme olarak ulaşım gürültüsü ile mücadelede kullanılabileceği düşünülmüştür. Boşluk yapısı ve narinliği sebebi ile bu halde direkt bariyer levhası uygulamaya elverişli olmayacağından, perlitli kaplama ek olarak sert bir destek yapısı gerekmektedir. Bunun için mevcut betonarme bariyerlere uygulanması bir yapıştırıcı vasıtası ile olmaktadır. Çalışmada kaplama ile yapısal uyumluluk açısından perlit esaslı sıva harcı kullanılmıştır. Akustik ses yutum performansı açısından değerlendirildiğinde perlitli kaplama, EN 1793-1 standardına göre, piyasada yaygın olarak kullanılan birçok gürültü bariyeri gibi A2 (DLα 4,95 dB) sınıfında yer almaktadır. Genel olarak kullanılan ses yutum katsayısı değeri ise yaklaşık NRC 0,3 olarak belirlenmiştir. Alternatif gürültü bariyer malzemelerinin yutuculukları incelenerek, kaplama için elde edilen akustik ses yutum değeri ile karşılaştırılmıştır. Perlitli kaplamanın sağlayacağı gürültü azaltım değerini belirleyebilmek için Datakustik firmasına ait ve Avrupa Birliği Komisyonu tarafından sonuçları Birlik Ülkelerinde geçerli kabul edilen CadnaA adlı gürültü haritalama yazılımı vasıtasıyla örnek bir alanda modelleme işlemi gerçekleştirilmiştir. Bu modellemeden elde edilen sonuçlara göre, mevzuatta verilen limitler üzerinde gürültüye maruz kalan kişi sayıları arasında mevcut bir bariyer üzerine perlit kaplama uygulanması durumunda %10 civarında bir azalma meydana gelmektedir. Bunu toplam aşırı rahatsız ve rahatsız kişi sayısı olarak ele aldığımızda gürültüden rahatsız olunan gürültü seviyelerinin, mevzuat gürültü limitlerinden farklı olmasından dolayı %5 civarında bir fark görülmektedir. Tezin devamında elde edilen gürültü seviyesindeki azalma ve gürültüden etkilenen kişi sayısındaki azalma miktarı ekonomik bir fayda olarak ele alınıp, bariyerin inşa maliyeti ve işletme maliyetleri ile karşılaştırılarak perlitli kaplamanın, belli kabuller altında, 50 yıllık yapı ömrü ile inşa edilmesinin ekonomik olup olmayacağı araştırılmıştır. Ayrıca Duyarlılık Analizi yapılarak kabul değişkenlerinin elde edilen sonuçlara ne kadar etkisi olduğu incelenmiştir. Yapılan çalışmada elde edilen fiziksel, akustik ve ekonomik analiz değerlendirme sonuçları; laboratuvar ortamında geliştirilen perlit esaslı kaplamanın trafik gürültüsü ile mücadelede kullanılmasının mümkün olduğunu göstermektedir. Ancak perlitli kaplama üretiminin, kullanım alanlarının yaygınlaştırılması ve yangına dayanım davranışı gibi konularda daha fazla geliştirme ve araştırmaya ihtiyaç vardır.

In this study, perlite based covering which can be used to increase sound absorption capability of noise barriers, especially for concrete noise barriers, which is one of the debating methods for environmental noise caused by highway traffic is examined in terms of design, expermental determination of physical and acoustic performance and costs. The covering is mainly made of expanded perlite and Turkey reserves considerable amount of perlite as a natural source. Turkey is ranked in five countries in the world as reserve and production capability of perlite. Perlite has widely used for several purposes in different industries. Nowadays, especially in construction sector, light weight thermal insulation mortar made of expanded perlite is used for thermal insulation for the building. Suggested covering is obtained by conditioning expanded perlite in a heated furnace for 5 minutes approximately at 1200°C which is very close to melting point of perlite. In the heating process, expanded perlite particles adhere to each other with gaps between. Expanded perlite sample in the seramic paper mould which is covered with magnesium oxide to prevent perlite stick to mould starts to shrink by losing volume. Volume loss ration is about %50 between the expanded form in the mould and glassified form after cooling. After cooling down the perlite sample, it becomes a pororus fragile structure in the form. After this process, due to the expanded perlite’s porous structure which is very similar with any other sound absorbing material, this covering is thought to be used as a sound absorbing material in debating traffic noise. The porosity of the sample mainly depends on the expanded perlite particle size range used in the design. Additionally, the number of layers which is made of different particle size of expanded perlite causes different porosity ratios in the perlite covering. Layering and use of different size of expanded perlite particles improves absorption capability of different frequency ranges for the perlite based covering. For any kind of sound insulation material, the gaps between front and back side are not allowed not to permit sound to propogate from one side to another. It is not convenient to use direclty in this fragile and porous form perlite based covering, so it is required a stiff backing board for physical strength. For this reason, use of this covering is on concrete noise barriers is by means of an adhesive. In this study, perlite based render is selected as adhesive to be structurally in compliance with covering. When evaluated in terms of acoustically sound absorption performance, the perlite based covering, according to EN 1793-1 (Road traffic noise reducing devices. Test method for determining the acoustic performance. Intrinsic characteristics of sound absorption), is classified as A2 (DLα 4,95 dB). This sound absorption class noise barriers have very common and widely use in the market. According to test results, commonly used sound absorption coefficient, NRC - Noise Reduction Coefficent, is determined as approximately 0,3 NRC. In this study, it was also examined sound absorbing capability of alternative noise barrier materials and compared with perlite based covering. To see the noise reduction effect of perlite based covering due to sound absorption capacity, a noise map modelling was conducted on a sample area with a software named CadnaA, a product of Datakustik company, whose results are considered valid in all EU countries by the decision of EU Commisison. In the modelling stage, certain assumptions and certain variables were taken into account only to see the acoustical performance of perlite based covering. Especially noise barrier location, weather conditions, road slope, traffic volume and heavy vehicle ratio are the basic asssumptions fixed. The variables to evaluate perforamance of perlite based coverng in the computer based noise modelling stage are noise barrier height, heading type of the noise barrier, with and without barrier cases and with and without perlite based covering cases. Evaluating the results of noise map modelling, when the perlite based covering is applied on an existing noise barrier, approximately %10 deacrease occurs in number of people exposed over noise limits given in the regulation comparing without covering noise barrier case. It becomes %5 when the total number of highly annoyed and annoyed poeple considered due to difference between noise regulation limits and annoyig and/or highly annoying limits. In the following stages of the thesis, taking reduction in the noise level and reduction in the number of people affected by traffic noise as an economical benefit and comparing with noise barrier construction and operation costs, application of the the perlite based covering was evaluated, under certain assumptions, economically feasible or not for the 50 years assumed as a life span of the concrete noise barrier. For the calculation of noise barriers contructional and operational costs, the unit costs were taken from Ministry of Environment and Urbanisation. The difficulty in calculation of benefits gained by reduction in noise levels was due that there were no survey or given money equivalent value for Turkey in one dB(A) decrease in traffic noise emissions.Additionally, noise related regulations in Turkey only giving environmental noise limit values. The concern in the number of annoyed and highly annoyed people is that munber of people exposed over the limits given in regulations are not representitive for number of annoyed and highly annoyed people. The difference between these two values effect calculation of benefit gained from reduction in noise levels. Money equivalent noise reduction values were taken from EU 6th frame programme HEATCO (Developing Harmonised European Approaches for Transport Costing and Project Assessment) project results and applied actualisation in the money values to get present value and used direct benefit transfer method (with gross domestic product –GDP ratio convertion) to transfer EU values to Turkey. In all calculations, payments of related noise barrier operation costs and monetarized benefits are multiplied by in the rate of inflation which has a changing value over the 50 years. In many sources estimation inflation rates for Turkey, are decreasing from %6 to %2 between the years 2015 and 2050. Due to the nature of Cost Benefit Analysis, a discount rate %2,5 selected. It is a very low rate for any kind of project but advised to be chosen in low rates in any other environmental projects with no direct or very small amount of money return. All costs and benefit values are converted into present value (PV) and Net Present Value (NPV), Cost-Benefit Ratio and internal rate of return (IRR) are calculated. Under the assumptions taken in noise modelling stage, all results are positive and showing that using perlite based covering for debating with traffic noise is acceptable. Using a perlite based covering on a noise barrier causes a rise about %11 in the initial cost of noise barrier construction. In additon, perlite based covering application causes a rise about %40 in the operation costs due to clogging cleaning operations for pores in the covering and fragility resulting in need for change of perlite based covering annualy in some parts of noise barrier. Even the rise in all costs, the benefit rise is about %34 when 7m height concrete barrier is covered with sound absorbing perlite based covering. Additionally, to see the effect of assumptions on feasibility analysis, sensivity analysis was conduted. Highest sensivity is observed for clog cleaning frequancy of perlite based covering. All other assumption are insensitive or less sensitive for up to %20 changes in costs. Evaluating all physical, acoustical and economical analysis results conducted in this study shows that the perlite based covering developed in the laboratory can be used as a solution for debating with traffic noise. However, perlite based covering is a new product so needs to be investigated for any other features and production technologies. It will help to generalise the usage area in several industries. In further studies and R&D projects, it is aimed to see fire resistance behaviour for tunnel fires with hidrocarbon heating curves, acoustical sound absorption coefficient determined by room method and any other physical tests required in EN 14388, noise barrier product standart, in TSE’s fire and acoustics departments of Tuzla Insulation Laboratory.