Bituminous Membranes

What is Bitumen?

Bitumen is a by-product of fractional distillation of crude oil, though it is also found in natural deposits. During crude oil distillation, light fractions (such as gasoline, naphtha, kerosene, diesel and fuel oil) are separated, leaving bitumen residue. Bitumen is a dense, high-viscosity, petroleum-based hydrocarbon composition. At room temperature, it exists in a semi-solid state. Bitumen is commonly referred to as asphalt, but asphalt is the name given to the mixture used for road surfacing materials composed of bitumen, gravel, sand and other binders. The bitumen content in asphalt is approximately 5%. Bitumen is also called tar or pitch. Tar is a by-product of coal carbonization, and pitch is obtained from the distillation of coal tar. [caption id="attachment_103638" align="aligncenter"] Figure 1. Bitumen being filled into drums[/caption]

Where is Bitumen Used?

Since ancient civilizations, bitumen has been widely used due to its excellent waterproofing and adhesive properties. Historical sources indicate that the Babylonians (founded: 1894 BC) used glazed bricks in building foundations and a layer of bitumen with ground coverings for waterproofing. The primary application area for bitumen is the construction sector. A large portion is used as a binder in asphalt for highways, airport runways and pedestrian pavements. Another widespread use is roof coverings. It is also used in various building materials such as floor tile underlayment and paint for sealing purposes. Bituminous membranes are preferred for waterproofing in roof and floor coverings.

Bituminous Membranes What is a Membrane?

A membrane is the general term for separator or semi-permeable materials in building materials. In other words, a membrane is a material used on roofs to prevent rainwater from penetrating concrete flooring.

What is a Bituminous Membrane?

Bituminous membranes are used as waterproofing material on foundations, curtain walls, basements, gardens, terraces and roofs of structures to protect against water damage and provide comfortable waterproofing for living areas. They are also suitable waterproofing materials for structures exposed to different loads such as bridges and viaducts.   [caption id="attachment_103639" align="aligncenter"] Figure 2. Bituminous Membrane[/caption]   Bituminous membranes are mixtures obtained by modifying high-quality bitumen with plastomeric or elastomeric polymer additives (such as APP and SBS). APP (Atactic Polypropylene) is a thermoplastic polymer that forms a uniform matrix within bitumen. SBS (Styrene-Butadiene-Styrene) modifies bitumen by creating a polymer network within it.

Types of Bituminous Membranes

1. APP (Atactic Polypropylene) Modified Bitumen Membrane: APP additive increases the softening temperature of bitumen from 50°C to 150°C. This causes bitumen to behave almost like a liquid, taking on a wax-like form. Furthermore, with APP additive, the cold bending temperature of bitumen can be reduced from 0°C to -10°C. This high tolerance of APP to temperature provides ease of application. 2. SBS (Styrene-Butadiene-Styrene) Modified Bitumen Membrane: SBS was produced in the late 1960s through block polymerization. With SBS additive, the cold bending temperature of bitumen was reduced to -30°C, thus obtaining bitumen membranes more suitable for cold climates. Due to the rubber in its structure, it is more flexible compared to APP. This flexibility makes it more resistant to wind, temperature changes, expansion and contraction. [caption id="attachment_103644" align="aligncenter"] Table 1. APP and SBS comparison table[/caption] Based on the above characteristics, it can be said that APP modified bitumen membranes are preferred in hot climate applications, while SBS modified membranes are preferred in cold climates. Additionally, SBS modified bituminous membranes should be used to provide protection against deformations that may occur in metal roof applications.

Bituminous Membrane Production Method

As a result of modifying bitumen with polymeric additives, its resistance to high and low temperatures is increased. Modified bitumen is impregnated into suitable glass fabric or polyester felt, and both surfaces are laminated with polyethylene film, polyethylene film-aluminum film, or polyethylene film-mineral stone. Polymer bituminous covering materials must be produced in accordance with the properties specified in TS 11758 – 1 standards and the application rules specified in TS 11758 – 2.

Applications of Bituminous Membranes

Bituminous waterproofing covers are used in virtually all areas where water could enter our structures: • Parking lots and highways with high stresses, railways used for transportation, structures such as bridges and viaducts, • Exterior walls below the level where water can accumulate outside the structure or where water pressure occurs, • Walls in contact with soil, foundations and floor slabs resting on ground, • Structures such as water tanks, artificial ponds and swimming pools, • Balconies, terraces and sloped roofs, • Retaining walls, concrete channels, • Bathrooms, toilets and washbasins are examples of areas where bituminous membranes are used. Sources 1- Birlik Çatı. Membran Nedir? Nerelerde Kullanılır? (2019, 17 January). Retrieved: 09.06.2020. www.birlikcati.com.tr 2- BİTÜDER. Bitümlü Örtüler Rehberi. (N.d.). Retrieved: 11.06.2020. www. bituder.org 3- Chen J. Bitumen. (2018, 20 May). Retrieved: 09.05.2020. www.investopedia.com 4- Curley R. Bitumen. (2017, 19 December). Retrieved: 09.06.2020. www.britannica.com/science/bitumen 5- Hanania J., Jenden J., Stenhous K., Afework B., Donev J., Bitumen. (2018, 25 June). Retrieved: 09.06.2020. www.energyeducation.ca 6- Humbarahane. Bitümlü Membran Su Yalıtım Malzemesi ile Temel Bohçalaması. (2016, 15 November). Retrieved: 11.06.2020. www.humbarahane.com 7- McNally T. Polymer Modified Bitumen. (2011). Retrieved: 09.06.2020. www.sciencedirect.com/topics/chemistry/bitumen 8- Mirolco. BITUMEN. (N.d.). Retrieved: 09.06.2020. www.mirolco.com 9- Patel C., Desai R., Gundaliya P. J., Bitumen Modified With Styrene Butadiene Styrene thermoplastic For Roofing Application. (N.d.). Retrieved: 11.06.2020. www.engineeringcivil.com 10- Soprema United Kingdom. Types Of Bitumen: SBS vs APP. (N.d.). Retrieved: 11.06.2020. www.soprema.co.uk 11- Tradesman. SBS vs. APP – What's The Difference? (N.d.). Retrieved: 11.06.2020. www.tradesmanroofing.com 12- Wikipedia. Babil. (2007). Retrieved: 09.06.2020. tr.wikipedia.org/wiki/ Babil   Öznur Kurt Product and Service Development Specialist Aleph Trade