Architecture:Roofing Materials.pdf
《Architecture:Roofing Materials.pdf》由会员分享,可在线阅读,更多相关《Architecture:Roofing Materials.pdf(22页珍藏版)》请在三一文库上搜索。
1、611 611 1.0INTRODUCTION The use of polymers as a roofing material is continuously increas- ing. The function of a roof is to protect the building from environmental factors such as light, wind, rain, snow loads, temperature changes, hail, and storms. Therefore, the material used on a roof must withs
2、tand those factors for many years. The performance of a material or system depends on the environ- ment and the degrading effects to which it is exposed. Until the early 1990s, methods of measuring the properties and predicting the durability of products were not well known, hence, much of the knowl
3、edge about building materials was based on experience from long-time use. An estimate of 90% of all flat roofs in Canada used in industrial, commercial, and public buildings are protected by bituminous roofing, and essentially all sloping residential roofs are covered with shingles having a bitumino
4、us-felt base. In recent years, changes in building practices have produced roofs of unusual design for which these materials were not suitable. This led to the development of new rubber and plastic roofing material, which, in turn, led to the development of rubber- and plastic- modified bitumen and
5、bitumen-modified rubbers and plastics.1 15 Roofing Materials 612Chapter 15 - Roofing Materials In 1993 and 2000, the commercial low-slope roofing market in the USA consisted of: The NRCAs 20002001 Annual Market Survey3 reported that in 2000, the low-slope roofing market accounted for 64.1% of the to
6、tal roofing market, a slight decrease from 68.7% in 1999. The roofing contractors predicted that the low-slope roofing market would be 63.3% in the year 2001. Most types of roofing materials are bituminous and synthetic (polymeric) roofing membranes. The most commonly used roofing and waterproofing
7、membrane is made by combining asphalt or coal tar pitch (bitumen) with felts or mats, or fabrics of organic or inorganic fibers. 2.0BITUMINOUS ROOFING MATERIAL The built-up roof membrane consists of bitumen, reinforced with roofing felts, and aggregates which protect the bitumen from the UV radiatio
8、n and oxidation. Bituminous materials have been used since 3500 BC. Because of their waterproofing, preservative, and binder characteris- tics, they were utilized by the ancients for the construction of houses and roads.4 Bituminous materials were also used by ancient civilizations such as Egyptians
9、 for construction, mummification, waterproofing, preserva- tives, and binders. Type1993220003 NewNew constructionRe-roofing construction Re-roofing Built-up roofing29.0%31.0%22.4%27.8% Single ply roofing38.8%33.3%38.1%33.6% Modified bitumen17.0%21.7%19.1%23.8% Metal3.5%1.6%4.3%2.5% Other types*11.7%
10、12.4%16.1%12.3% * Other types = tiles, PUF, liquid-applied, asphalt shingles, metal 613 The asphalt is a complex mixture of organic and inorganic com- pounds and their complexes. Some of the organic compounds are aliphatics, aromatics, polar aromatics, and asphaltenes. Polar aromatics are respon- si
11、ble for the viscoelastic properties of asphalts.5 Over the years, multilayers of tar-based waterproofers replaced the hot asphalt used in roofing. In early 1900, asphalt became available from petroleum refining, and it was followed by oxidized bitumen interlaid with roofing felt and then alternated
12、with a mineral base sheet.4 Asphalt-based materials are used extensively as binders, sealants, and waterproof coatings in diverse applications because of their low cost, inherent cohesive nature, weather-resistant properties, and ease of processing in the molten state.6 Despite its natural viscoelas
13、tic properties, asphalt cannot be used as such in roofing applications because of its inherent limitations, such as brittleness at low temperature and flow properties at high temperature. Therefore, studies have been done to improve the properties of bitumen. Combining bitumen with natural or synthe
14、tic rubbers or lattices, new materials with higher elasticity, low temperature flexibility, higher strength, and better fatigue resistance can be obtained. Polymer-modified bituminous membranes were developed in Eu- rope in the mid-1960s and have been in use in North America since 1975. The polymeri
15、c systems have varied from natural rubber to more complex synthetic systems such as block copolymers and polymer blends. Most common polymers used as modifiers are polyisobutylenes, polybutadienes, polyisoprenes, styrene-butiene-monomer, styrene-butadiene-rubber, butyl rubber, ethylene-vinylacetate
16、(EVA), atactic polypropylene (APP) as well as natural rubber. Polymers, such as atactic polypropylene or styrene- butadiene-styrene (SBS), impart flexibility and elasticity, improve cohe- sive strength, resist flow at high temperatures, and toughness.7 They are the most widely used modifiers of bitu
17、men-based roofing materials. 3.0SYNTHETIC ROOFING MEMBRANES Polymers such as poly(vinyl chloride) (PVC), ethylene-propylene- diene monomer (EPDM), chlorosulfonated polyethylene, ketone ethylene ester (KEE), reinforced polyurethane, butyl rubbers, and polychloroprene (neoprene) have proven to be suit
18、able for roofing membranes.4 In the last ten years, a new synthetic roofing material (thermoplastic polyolefins) Section 3.0 - Synthetic Roofing Membranes 614Chapter 15 - Roofing Materials (TPO) has entered the market. Polymeric membranes have advantages and disadvantages.8 Advantages: Ultra-lightwe
19、ight (for unballasted, adhered membranes) Adaptable to irregular roof surfaces Isotropic physical behavior Superior architectural quality (color) White membranes have general superior heat reflectivity (for cooling-energy conservation) Better elongation (up to 800% at 21C, 70F) Superior performance
20、at sub-zero temperatures flexibil- ity down to at least -40C, (-40F) for some materials Easier application Fewer weather restrictions on application Less hazard from moisture entrapment during installation Easier repair of punctures, splits, tears Easier flashing applications at corners and irregula
21、r sur- faces where stiffer built-up roof materials are difficult to form Possible greater reliance on factory-manufactured mate- rial quality Disadvantages: Greater requirement for good workmanship More limited range of suitable substrates Less puncture resistance. Hence, greater vulnerability to tr
22、affic damage Lack of performance and design criteria comparable to those available for built-up roofs 615 4.0APPLICATIONS Regardless of the chemical composition of the materials, in a number of applications, such as in roofing, the materials are exposed to a wide range of temperature, wind, and load
23、 conditions. For example, in northern climates, the temperature of an asphalt or black roof membrane could be as high as 100C on a hot summer day and as cold as -40C in winter. Moreover, the material has to sustain the stresses generated by thermal expansion and contraction. Therefore, a combination
24、 of high- temperature and low temperature performance is required from end-use consideration. Critical properties such as high softening points, good tracking and flow resistance at elevated temperatures (6070C for modi- fied bitumens), good impact and crack resistance, good cohesive strength and hi
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- Architecture:Roofing Materials Architecture Roofing
链接地址:https://www.31doc.com/p-3732643.html