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1. Introduction: The properties that make bituminous materials suitable for road applications also make certain grades suitable for a whole range of other applications. These properties are: - waterproofing Bitumen has a vast range of uses for bitumen from membranes to surface coatings to battery boxes to inks. 1. 1 Definition Of Industrial Bitumen. For the purposes of this technote industrial bitumens are bitumen manufactured for the purpose of applications other than road pave. In some instances road pave bitumen may be a base for an industrial application . 1.2 Modes Of Manufacture. The two main methods of manufacture that will be considered are: a) air blowing 1.3 Modes Of Delivery. To be useful the bitumen must be in a fluid state. This means that the industrial bitumen must be handled hot, made into a cutback, or emulsified. 2. Manufacture Of Industrial bitumen. 2.1 Air Blowing. The chemistry of air blowing has been considered in detail in Manual 2 part 2. Industrial bitumen are often used in applications where the binder must have a high resistance to heat and flow yet remain flexible . This usually means a hard bitumen with high softening point and low penetration. Blowing curve shape is quite different for an industrial bitumen compared to a road pave. The specification requirements are quite different in terms of the combination of softening point and penetration. From our knowledge of bitumen chemistry it is obvious that to achieve the degree of structure required for industrial bitumen requires quite different feed stocks. The difference in composition between an industrial and road pave bitumen is that asphaltene levels are much higher, oil levels are similar but resin levels are low. This means that most of the resin materials have been converted to asphaltenes, yet the oils remain at a level that is high enough to give flexibility but not high enough to reduce pen or softening point. This cannot be achieved with the high aromatic feeds used in road paves. 2.1.1 Blowing feeds. The main mechanisms for creation of high degrees of structure are asphaltenes creation and crosslinking. Asphaltenes of high polarity will give the best results as the structure will be reversible and more flexible . That is less brittle. The blowing feeds can be quite different to achieve the final result. The blowing curves must be established for different feeds and the technology of prediction of properties from composition is not as advanced as for road pave. 2.1.2 Blowing method. a) Conventional. Industrial bitumen have traditionally been made with air sparging in continuous or batch processes. . The reaction is exothermic and the process must be kept under temperature control. The material is sampled in a batch process and tested for penetration, softening point or both. Specifications are in these terms. In a continuous process the residence time is determined in advance and tests done on the output. Reaction temperatures are 280C. b) Biturox Industrial bitumen may be made in Biturox type plants. This is similar to the conventional process except that the temperature control and steam stripping is achieved by pipes which feed the water and air into the reactor. The bubble size is controlled by the injection system and a series of turbines and coalescing plates, and hence the reaction rate is controlled. Reaction pressure and temperature is controlled to about 250-260C and 2 bar. c) catalyst Almost since the first blown asphalts were developed there has been efforts to control and alter the process. This has been by materials referred to as catalysts but as the material is usually used up in the reaction this is actually a misnomer. They actually chemically alter the bitumen, probably by functionalising bitumen components with hetero atom groups of various types. There have been many patents issued (and expired) for such materials. These have included: i) Oxidising Substances such as: Nitric oxide, nitric acid, perborates, boric acid,boron triflouride, ferric chloride,zinc chloride, aluminium chloride, copper sulphate, sulphur oxides, sulphuric acid, phosphoric acid, phosphorous pentoxide. phosphorous sulphur compounds and carbon tetrachloride.. Of these the most effective appear to be ferric and zinc chloride, zinc chloride and phosphorus pentoxide. ii) Finely Divided materials with active surfaces such as: Bentonite, finely powdered coke, and oxides, sulphates and soaps of metallic compounds ( Iron, copper, zinc lead etc). Such systems are not greatly effective. The materials are used by addition of levels of 0.1-3% into the blowing charge during the preheat stage of the process. If the agent is water soluble it can be added via the water sprays or injection pipes. Because the "catalyst" reacts with the bitumen rather than actually promoting the air interaction then blowing times are not always reduced. If they are it is because the kinetics of the reaction with the catalyst is faster. As different structural elements are built up the rheological characteristics of catalyst blown bitumen can be different to straight air blown. . The penetration index of the catalyst blown materials has been significantly improved. This means less cracking at low temperatures but equivalent high temperature properties as indicated by the softening point. Different catalysts create different reactions and thus different properties. 2.2 Chemical modification Chemical modification of bitumen has been carried out for a long time these have included the use of sulphur (1866), chromium trioxide, maleic annhyride, hydrogen chloride gas, and acids such as phosphoric acid, sulphuric acid and nitric acid, alone and in combination. It is beyond the scope of this manual to deal with the detailed chemistry of these reactions, however, they appear to operate on increasing the polarity of the aromatic, resinous and asphaltene materials. Sulphurising, was a particularly important method used prior to the development of blowing processes. In this process 20-25% of sulphur was added to bitumen at temperatures below the boiling point of sulphur. ( around 220C) Chlorine has similar effects to sulphur and oxygen. It too dehydrogenates the bitumen and increases functionality. This may also be achieved with acid. Recent work on using mixed acids, sulphuric and nitric acid to generate nitronium ion and to allow addition reactions with resins to create increased polarity and hence structure has shown that elasticity and viscosity may be increased in this manner. 2.3 Polymer Modification. As in the case of roadpave bitumens there are limitations to the rheological enhancements that may be achieved by the use of optimisation and modification of the bitumen components themselves. Polymers present a method by which bitumens may be modified to improve their properties. As in the case of roadpave bitumen the modification will improve low temperature performance by reducing propensity to crack while maintaining high temperature properties. Modification can take two approaches. a) Modification of blown bitumens 2.3.1 Modification Of Blown Bitumen. a) General Several types of polymers have been used to modify bitumen for industrial applications. Notably their use in roofing . Standard oxidised grades have given good performance over many years in roofing felts and asphalt shingles, however, with the advent of light weight construction methods for rooves and increased roofing insulation the demands placed on the product have increased. Lightweight roofing increases the flexing of the roof both by greater movement and expansion and contraction due to daily temperature variations. use of roofing insulation increases the temperature range experienced as well. At night heat does not escape through the roof and hence the roofing felt experiences much lower temperatures at night. The two polymer types that have had significant success in roofing, plastomeric polyolefins and thermoplastic elastomers. - Of these the majority have been atactic polypropylene (plastomeric) and SBS ( elastomeric). The SBS polymers appear superior. 2.3.2 Modification of Road Pave The preparation of bitumens especially for industrial applications is acceptable where market size is significant and or road pave bitumens are not produced. In some cases however it is beneficial to have a system where other grades may be modified for industrial applications. In many countries road pave production is of greater importance and so modified road paves would seem to be a good approach. Industrial bitumen have their rheology characterised by penetration and softening point. This gives an indication of their thermal susceptibility and the high temperature (RBSP) and low temperature ( pen) performance. However as the manufacturing process has been based on blowing methods using conventional blowing stills then the grades have been based largely on what is possible and meets the base requirements of the customer. Polymer modification gives the possibility of a controlled modification of the rheology and hence tailor making bitumen to meet specific requirements. The availability of measuring the rheological characteristics more closely also gives the possibility of typing rheology to use. The rheological profile required is not dissimilar to that required for road pave. The material must not crack at low temperatures, and must not flow at high temperatures- except in fabrication. 2.4 Clay emulsions. Clay emulsions are more a method of delivery of industrial bitumens, however they are also filled systems and the films produced impart special properties to the binder. Also they will allow the use of roadpave, softer bitumens as a base. An example of this is Emoleum emastak. This product has a wide range of uses from grafting trees to repairing water tanks to coating buildings. Applications of clay emulsions include - protective coatings a) Theory Clay emulsions are analogous to other bitumen emulsions ( manual 4), they are formed by the mixing of two immiscible phases- bitumen and water with an emulsifying agent, in this case clay. The clay is required to have a substantial amount of colloidal matter. This is mixed into the bitumen or may be part dispersed in the water phase. In general such systems are filled with Talc and other clays and may also contain dispersing and coating agents and pH stabilisers such as dichromates. The active colloidal material such as bentonite or Kaolin clay can be added in a concentrated form via the water phase. Clays such as bentonite swell in water and can carry a net negative charge. This forms a double layer this increases viscosity, when bitumen is added these particles can coat the bitumen, which is not miscible with the water. This has the effect of both stabilising the bitumen/water/clay mixture and as well allowing viscosity adjustment with extra water.
b) Suitable Bitumens. Any emulsable bitumen of any type may be used. If industrial or oxidised bitumens are used they are generally more difficult to emulsify and require a higher shearing effort. In this case a colloid mill with a high horse power. For softer bitumens a sigma or blade mixer is adequate. c) Suitable Clays Mineral clays of the monto, orillite, kaolinite and attapulgite type can be used. As these materials vary greatly in coilloidal strength, particle size and degree of hydration they will produce different results. d) Modifiers. The greatest variation in formulations based on clay emulsions is the pH ( 5-9.5 ). Control of pH both during emulsification and afterwards is critical to the stability of the emulsion and the particle sizing which will , amongst other things have an effect on how fast the film breaks and cures and also on the permeability. Suitable agents are acids, and acidic salts such as aluminium phosphate, sodium phosphate and potassium dichromate. e) Manufacture. i) Emulsification: The factors that need to be taken into account are - Temperature and viscosity of bitumen and the water/clay These require experimentation to arrive at. Typical emulsification temperatures are: Bitumen: 30-40%, 130-140C ii) Equipment: The elements required are: - tank for dispersing clay in water VSS can supply all equipment needs For example in the manufacture of waterproofing compounds the bentonite emulsifier is combined with water at 50C in a high speed mixer. The extra fillers such as talc and other clay is mixed in a pugmill/ blender with water( together with any additives) and the emulsifier added. The bitumen is metered in at 140C slowly at about 10 lt/min. The emulsion is thus formed and filled at the same time. The final product is adjusted with water to required viscosity. f) Emulsion properties. The properties of clay emulsions depend on the exact formulation of fillers, bitumen and emulsifier and their physical properties. Bitumen must be selected for the end use and fillers added to give final film properties. However for adequate application the emulsion properties are also important. The following properties are controlled by the amounts and type of clays/ fillers and bitumen. - bitumen content i) Bitumen Content. This can vary from about 30% to 60% depending on whether the emulsion is filled or not. Emulsifier contents vary from 2-5% ii) Consistency. Clay emulsions are shear thinning, that is they reduce in viscosity with shear. The consistency will change with increasing bitumen or clay content. iii) Stability. The emulsion will remain stable but over time will gel due to positively charged ions in the clay or electrolytes in the water phase. Freezing will also destabilise the emulsions. iv) Application. The shear thinning effect allows the emulsion to be painted by brush or sprayed. Viscosity needs to be controlled and the emulsion form also allows water to be added to do this. Wetted fillers may be post added for different applications. This includes use of rubber, sawdust, cement slurry, vermeculite, fibres, latex etc. v) Film Drying. After application the film cures or hardens by water loss. In the initial stages the films are very permeable and dry quickly. As they cure this drying rate becomes slower. The level of filler also has a significant effect. A dry film of about 1.6mm has a permeability of 1.0-2.5 perms which goes down to about 0.6-1.0 after 60 days weathering. Drying to firm takes about 1-5 hours to touch dry and about 12-24 hours for full cure ( 25C 50% humidity). This varies depending on the product. vi) Adhesion/ Cohesion and flexibility. This depends on bitumen type and filler levels. Plus any other additives such as rubber or cement. Rubber will increase flexibility, cement will increase strength but decrease flexibility. Adhesion depends on the cleanliness of the substrates and the viscosity of application. Wetting viscosity is around 100-15,000 cp. Remember it reduced in viscosity during application so the rest viscosity may be much higher. vii) Curing/ Weathering As the emulsion dehydrates bitumen is deposited in a structure consisting of coalesced bitumen and bentonite threads. This reinforces the film. Other fillers are distributed through the matrix and coated with bitumen. This allows movement at low temperatures and prevents movement at high temperatures ( up to 50C). The films weather and this will reduce permeability over the first few months by about 30%. Films can last for many years without becoming excessively brittle, depending on formulation. Such surfaces can be protected by painting with water based paints. g) Products and Uses. As the systems are emulsions they have all of the low temperature application and environmental advantages of all emulsions .Clay emulsions an be applied to most clean surfaces and impart the excellent waterproofing, chemical resistance and insulation properties of bitumen. This gives them application in: - Roofing: Filled versions with fibres are useful for roofing seals. - Water proofing Filled versions may be used for foundation sealing, building walls below ground, sealing water tanks. - Anti sweat coatings for moist areas such as air conditioning ducts - Metal and masonry coatings For pipe coatings, metal walls, bricks etc. - Plant Grafting The emulsions are non toxic so can be used for grafting plants. - Primer coatings Application on to metal, wood, masonry, cement before other protective coatings. - Adhesives For polystyrene, wood flooring. - Flooring Mixed with fillers and cement slurry or graded aggregates. - Insulation mastic Filled and used as an insulating layer between walls. - Paper Sizing Mixed with alum, unfilled emulsions may be used for paper sizing. 2.5 Industrial emulsion Cutbacks. a) Formulation and Manufacture. In some instances it is useful to cutback industrial bitumen for use in applications where a solution is desirable. Mobil manufacture a range of such products. The solvents vary from toluene and kerosene to chlorinated solvents for inflammability. Solvent handling is outside the scope of this manual but manufacture of industrial cutbacks may be dangerous, especially with low flash solvents such as toluene. Careful handling, venting and use of water cooled condensers on mixing tanks is essential. In line blending is recommended but tank mixing is also possible. Cutbacks for road pave have been discussed and these manufacturing methods are satisfactory as long as the safety question is observed. Section 3 Specifications The following section examines different specifications from different countries for the industrial bitumens themselves. The specifications are overwhelmingly based on penetration and softening point data. 3.1 USA. 3.1.1 Main applications: The main applications of industrial type bitumens in the USA are: - Ditch and Pond Linings ASTM 2521- damp proofing and water proofing ASTM D449 - Primers for roofing 3 ASTM D41 - Roofing ASTM D312, D1227. - Aluminium paint - under body coatings - floor mastic - adhesives Of these roofing is the most important. 3.1.2 Specification Testing. Specifications are based solely on penetration at 25C, 0C, and 46C as a measure of consistency and thermal susceptibility, ie rheology over a range of temperatures. The draw back is that these are carried out under different shear rates and can only be an indicator. The softening point is used as an indicator of very high temperature consistency and ductility for flexibility. Safety and purity tests such as flash point, loss on heating and solubility in trichloroethylene are also used. Specific tests for other applications and development are also often done these will be mostly covered in application but several US tests have had extensive use. these are. - Weatherometer Testing. Durability in service is a prime concern. Oxidation can lead to embrittlement, cracking and water ingress. This is very important for roofing. In weathering testing a thin section of bitumen coated on an aluminium panel is subjected to cycles of temperature, ultra violet light and water. This is an accelerated test ASTM D529-59T. The weatherometers are manufactured by the Atlas company of USA. Cycles used are: 1. Exposure to light to produce a black body temperature of 50-80C. This is the oxidation phase. 2. Exposure to water spray at 7C-8C to simulate rain, this washes away oxidative coatings that may protect the surface. 3. Exposure to thermal shock by water spray then cooling to -20C. The test is followed by measurement of a physical property of the material eg impact strength or crack formation. Crack formation is detected by use of a spark gap detector. - Stain Testing The Schweyer test is a way of checking for cracked product in the blown bitumen. In service such oils will bleed and stain surfaces, especially roofing. Loss of these oils also leads to embrittlement of the bitumen . This test involves placing a sample of bitumen in the form of a disc between leaves of cigarette paper. There are 17 leaves and the bitumen is placed in the last two. The book is heated in an oven with a weight of 400g on top at 55C. After 5 days the number of stained leaves are counted. The number must be less than 7. The ASTM test uses more accelerated conditions ( ASTM D1328). A bitumen plug about 2cm high by 1.2cm by 4 cm is made in a mould. 31 discs of cigarette papers are held against it in a jig with a torque of 28cm.kg( 25 lb.in). A pressure fitting is screwed to the other end and a nitrogen or air pressure of 50 psi ( 3 bar) is applied. at 100C for 18 hours. The maximum number of stained papers is determined. - Oliensis Test This is ASTM D1370 and is a compatibility test. This test is mostly used for roofing. In this process a layer of bitumen is placed on felt that has been saturated with bitumen. If there is a gradient of oil concentration set up then oil will migrate from one to the other causing embrittlement. In this test a 1mm layer is spread in a small pan and allowed to cool. The surface is dusted with a roofing grade of talc and small drops of the saturant are put on top. The specimen is put in an oven at around 60C for 72 hours. If there has been significant exudation or oil transfer from the bitumen a saturant drops will develop a dark oily ring. The width of the ring must not exceed 0.5mm. 3.2 United Kingdom. 3.2.1 Main Applications In the UK there are two grades of industrial bitumen , the oxidised grades and the so called hard grades ( also produced by oxidation). This is 22% of the total bitumen market . Specification is based on the grades rather than application. - BS 3690- Part 2 is "oxidised grades" The harder grades of penetration bitumen are used for some industrial applications such as lubricants and saturants. The rest are the oxidised type. Applications include: - Roofing (>70%) - 85/25 and 95/25- Flooring (>8%)- 85/25 - Pipe Coatings - 85/25, 115/15 - Mastic - 15pen, 35 pen, 50 pen - Cables and batteries- 85/25 , 95/25 - Wall board and paper coating- 15 pen, 35 pen - joint sealants- 15 pen 35 pen, 50pen - automotive sealants and paints. H80/90, H100/120 Overwhelmingly 85/25 and 95/25 dominate the market and MOCL only manufacture these. 3.2.2 Specification Testing. As has been indicated above the materials are specified on penetration and ring and ball softening point to characterise the rheology of the bitumen. Purity and staining are checked by loss in heating and solubility in TCE. The hard grades of oxidised bitumen have lower penetration indices than the oxidise grades, varying from 0 to +2, compared to +2 to +8 for the oxidised grades. The lower PI materials tend to be easier to process and less brittle. Users of industrial grades of this type are likely to have similar tests added to those of the BS spec. These include tests on elasticity such as fraas point ( cold bend temperature), breaking stress in tension, elongation at break . 3.3 Australia. 3.3.1 Applications Australian usage of industrial bitumen is low. They are based around 90/18 grade mostly. They are divided into specifications based on oxidised bitumens and cutbacks made from them , or sometimes road paves, C80, C320 and C170. There are no Australian standards for these products The uses are also listed. The major uses are - automotive Little roofing is done with bitumen in Australia. 3.3.2 Testing The industrial bitumens are specified according to penetration at 25C and softening point. Safety and purity are tested by flash point and solubility. Special testing is often carried out by the customers for different applications, especially automotive. This is done for the final composite product and is outside the scope of this manual. 3.4 France 3.4.1 Applications Little information is available. There is a thriving roofing market. 3.4.2 Testing The standard penetration/ softening point specification is used. Most users would also measure Fraas point. 3.5 Philippines 3.5.1 Applications. In many developing countries industrial bitumens of all types are widely used. main applications are: - Roofing 3.5.2 Testing Testing is carried out using the penetration and softening point to characterise rheology . Ductility is used as an indication of flexibility and purity is ensured by a solubility test. Cutback is characterised by viscosity and solids. Section 4: APPLICATIONS The applications of industrial bitumen are many bitumen is useful anywhere there is a waterproofing , insulation or chemical resistance problem to be found. This section covers several major applications that a manufacturer of bitumen might further examine as possible markets and apply some of the principles and approaches to product design discussed in the earlier sections and manuals. The applications to be discussed are: 1. Roofing - automotive 4.1 Roofing 4.1.1 Introduction There are two basic types of bitumen roofs - Built up roofing: These are roofs built in place by building up layers of bitumen saturated felts, paper, or other substrate (eg fibreglass) protected by the bitumen. Mineral aggregates or other coating is applied at a top surface. - Prepared Roofs These are roofs applied as finished products made in a factory. They include membranes in rolls and surfaced shingles ( aggregate or metal coated. The substrates may be felt, paper, metal or mineral. In Europe and USA a very large use of bitumen is in roofing. This is divided into hot and cold applied materials. The majority of use is in pre-prepared roofing shingles or membranes that are applied by torching ie adhesion to a roof by heating, adhesive bonding with hot materials ( mopping asphalts) or cold bituminous materials ( emulsions). Sometimes the materials are self adhesive with tack additives . Filled mastic materials have also been used ( although these are more common as flooring ( covered in building). In Europe there is now a tendency to use polymer modified materials for roofing felts ( see section 2.3.1) , in 1990 this accounted for 65% of the total 700 million m2 of roofing used. In USA the use of roofing felts or coated and saturated substrates of felt, paper or metal is a wide market of several million tonnes per year. It represents in excess of 85% of the total roofing market. Roofing asphalt began in the late 19th century with the use of trinidad lake asphalts and later petroleum bitumens. The development of blowing processes and the felt process further advanced the industry. In 1890 the first aggregate surfaced roll roofing was made. Shingles were invented and now dominate the domestic market, where built up roofing is more suited to commercial buildings. 4.1.2 Built Up Roofing 4.1.2.1 General Description This is generally used for commercial buildings with large and flat to low pitch roofs. Because there is only a low slope the roofing must be continuos to ensure waterproofing. This is true for any slope of less than 1:8. The materials may be prepared impregnated felts or membranes glued with hot bitumen or other material to the roof. The roof is built up then of a layer or several layers of these felts and hot bitumen or cold application. 4.1.2.2 Hot Application Materials The hot system uses basically three elements, a saturated felt, mopping asphalts applied hot for adhesion and waterproofing and a coating of bitumen with often a cover of particles. a) Bitumen Materials. i) Hot Coatings and Mopping Asphalts. Bitumen is used both to adhere the felt to substrates( mopping asphalt) and to coat and protect the surface.( Coating). The general bitumen types and specifications was discussed in section 3. Blown materials of 90/18, 85/25 etc are widely used). The main requirements are that the bitumen should be easy to apply, impermeable, aging resistant. It should be flexible enough to resist cracking at the lower service temperatures encountered and stiff enough to withstand deformation due to roof movements or floor traffic at the highest temperature of service. it also needs to be able to withstand the thermal cycling of service without cracking or deforming. For coatings , fillers and stabilisers are often added to reduce cost , improve durability and weathering resistance . These include, limestone, silica, sand, fly ash and fibres such as cellulose and inorganic fibres. Asbestos was extensively used but is now largely avoided due to health problems. Pigments may also be added, especially with albino or synthetic clear bitumens. Mineral toppings are often used, fine or coarse particles such as aggregates, graphite, vermeculite , mica, quartz and slag are extensively used. These give further protection. This is an ideal application for polymer modified bitumens. ii) Felt saturant The bitumen used as saturant for the roofing felt must have a viscosity low enough to evenly soak the felt, it must have a penetration > 40 so the felt will not crack, it should be ductile, its softening point should be about 50-70C, it should have no volatile materials, and a high flash point. High penetration grades of bitumen ( 100-200) are ideal. Sometimes fungicides , herbicides and other mildew retardants are added to increase life. b) Felt i) Substrates. Substrates used are sheets composed of organic or inorganic fibres. Asbestos was widely used as well as rags, hence the term Rag Felts. However synthetic and cellulosic type fibres, as well as fibreglass and woven polypropylene , polyester and nylon are more commonly used today. ii) Composite. These are manufactured on machines similar to paper manufacturing machines . They consist of a substrate saturated with a soft bitumen. The substrate passes through a sump bath then is rolled and cooled before winding on to rolls. these rolls are large and designed to cover 200 or more square feet of roof. The felts are saturated to 140-225% of their weight with the bitumen. 160% is a good aim to ensure waterproofing. Saturation is quite fast through automatic machines at in excess of 100m a minute. The saturated felt is the basic unit or plie of the system, the mopping asphalt is used to adhere it to other plies and the roof surface and to provide the base of the final roof coating. 4.1.2.3 Cold Application Materials The cold system is analogous to the hot system but requires slightly different materials. It has three elements, the cold process felt, an emulsion or cutback adhesive and a cold applied surfacing. a) Bitumen Materials. i) Adhesives and Coatings. The adhesive used is based on industrial bitumens similar to those for hot application. They may be emulsion or cutback. Generally highly volatile solvents are used for cutbacks. They must bond securely to both the roof surface and the felt and dry quickly. In drying they must form a continuous waterproof film. They must be formulated to be applied easily with brush, spray or roller. The adhesive bonds formed should be higher than the tear strength of the saturated felt. This may be a cutback cement or a clay emulsion may also be used. This has been discussed already. ii) Surfacings. Coatings or surfacings must be easy to spread and form a protective and weatherproof layer, bonding securely to the upper layer of felt. The coatings may be emulsion or cutback,. each has its advantages and disadvantages . Emulsions are safe and easy to use, can be used on damp roofing materials but are slow to cure and subject to wash off in early life. The early permeability of emulsion films ensures complete drying and reduces propensity for the coating to blister. Clay emulsions are useful for this application forming very stable films. Cutbacks on the other hand cure quickly and are easy to apply, however cutbacks form tight films that can trap solvent, this can lead to blistering later in life. The base bitumen used in this application is similar to that of the hot process. Fibrous materials or aggregate coatings are used as for hot systems. iii) Felt Saturant As for hot application. b) Felt The felt requirements are that it provide a surface for the coating, adhere to the adhesive and will allow the solvent or water to evaporate to form a waterproof bond without blistering. Synthetics are mostly used today instead of felt. i) Substrates. Synthetic or wood fibre substrates are used to meet the requirements iii) Composites. The final felt is manufactured in a similar fashion to the hot process. 4.1.2.4. Roofing Systems. A built up roof is thus the build up of a combination of several membranes of roofing felt adhered to the a roof by bitumen in a hot or cold form. The construction is capped by a sheet or by a surfacing of hot or cold bitumen, filled or unfilled, modified or not and with a granular particle coating or not. As the service life needs to be improved the number of felt plies and coating type and composition may be varied. 4.1.2.5 Test Requirements The main test requirements for roofing materials are related to the properties of the various components, as has been indicated in the tables and discussion. Little formal specification of the mechanical properties is possible in built up roofing. Physical properties of materials have been developed on trial and error. Coating weights, felt saturation levels and application rates are important to control. For purposes of specification fire resistance is a key area and should be considered. The main tests carried out are a) Flame exposure That is the tests measure how easy it is for the materials to ignite or spread fire. 4.1.2.6 Service life a) Classification. Often roofs are classified in terms of their life expectancy. 20 years would represent a goof life, it would be constructed of good materials using 5 plies of felt and covered by aggregate 15 year roofs would be 4 plies and 10 years 3 plies. b) Failure Modes. Premature failures are usually due to: i) Blisters. These may arise within the plies or at the mopping asphalt or adhesive layers. They are avoided by good construction practice. ii) Flashing Failure. This occurs at the edges of plies and is due to insufficient overlap or poor preparation of the roof iii) Traffic on the roof, especially before curing has completed. Long term failures. These arise from cracking due to the aging of the bitumen to a stage where it becomes brittle and can no longer withstand the flexing of the roof, the temperature cycling or extremes or the traffic that the roof takes. This is best reduced by good design and application and the correct selection of materials. c) Maintenance If aggregate is not used to coat the original roofing surface then a periodic cold coating of clay emulsion will extend the life of the roof. In some instances this may be painted with a water based paint. d) Vapour Barriers and Insulation. Condensation under a roof can lead to damage to both the roof and the building. . This is particularly a problem where ventilation is inadequate. Insulation can add to such problems and when used should avoid collection of moisture. To assist in protection a membrane of bitumen and a saturated insulation system ( using soft bitumen) should be used. 4.1.2.7 Application. a) Roof Surfaces. The roofing must adhere to the roof substrate. This roof must be mechanically sound to perform its function. Wood roofs should be smooth and firm with cracks and joints covered by metal strips. Plywood roofs or decks have standard requirements from the manufacturer and these should be followed in installation. Poured decks of concrete should be smooth firm and clean and well set. Precast roofs should be smooth with all open joints grouted and covered with metal strips. All roofs that are non nailable require installation of nailable wooden strips at the edges for flashings. b) Hot Application. i) Non Nailable Surfaces with Aggregate or slag final Surface. - The surface needs to be primed with a cutback primer ( ASTM D41) based on bitumen or a rubber primer such as polychloroprene. This applied at about 0.01 gallon per ft2. This is allowed to dry completely. - Bitumen ( 85/25) is mopped on to the surface and plies of felt embedded in. Each layer of felt is mopped for the next layer. The mopping bitumen is applied at 230-300C at about 20 lb/100 ft2 over the full width of each sheet. To the required number of plies-4-5. - The entire area is poured with 50-60 lb/ft2 of roofing bitumen ( 90/18, 95/25 ) and spread by hand. - Immediately slag or other aggregate is spread and embedded at 300-400 lb/ 100ft2 ii) Nailable decks - If the surface is wood sappy or rosin spots must be gritted or sheathed with bitumen coated papers. - Alternative layers of felt and mopping bitumen are layed with 20lb/100ft2 of bitumen per layer. - Each plie is nailed with barbed roofing nails at the edges at 12inch intervals. - The entire surface is then coated with bitumen at 25 lb/100ft2. iii) Cap Sheets on Non Wood surfaces. These are surface sheets for make ups. - The surface is primed with a bitumen primer at 0.01 gallons per ft2. iv) Nailable decks with Gravel or Slag surfaces. As for non nailable surfaces a) but no prime is used and the layers are nailed. Aggregate sizes are about 10- 12mm. b) Cold application - Adhesive is sprayed or rolled to an even film on to a prepared surface 4.1.3 Prepared Roofing There are two main types of pre-prepared roofing. - Roll Roofing The bitumen composite consisting of backing/ saturated felt/ surface / and mineral coating is formed into a roll to be laid out in application. The roll is then adhered to the roof. - Shingles or tiles These are similar to rolls except they are cut into single tiles or strips of tiles to be adhered or fixed to a roof surface. 4.1.3.1 Manufacture. a) General. The manufacture combines the elements of the roofing, the steps are i) saturation of the felt ii) coating of the felt ( cracking and surface) iii) Application of the granular materials. b) Saturation. The saturated felt is the backbone of the product. It allows the roofing to be layed in rolls or cut into shingles. It provides a base for the backing and the weather proof surface. To perform the felt must be saturated to close to its capacity. The final surface must be touch dry with no rich or shiny spots, such imperfections lead to poor bonding of surfaces. The main variables are : - the felt type- porosity i) porosity Measured by the kerosene absorption test. Dried felt is impregnated with kerosene under vacuum. The volume of kerosene absorbed is calculated and expressed in cm3/100g of felt. Thus the porosity is found. 80% or higher is an acceptable result for this test. Paraffin oil is applied and the time to soak through gives a saturation time. These two figures allows residence time and coating line speed to be established. ii) Wetting. Interfacial wetting is not a key factor as bitumen and felts do not vary much. iii) Viscosity is very important to ensure coating. iv) Residence time. Determined from the porosity tests. v) Temperature This changes viscosity but also the percentage of saturation and distribution of the saturant materials. The saturant can also harden during running and this musty be adjusted for in the temperature. vi) Other. Moisture in the felt can result in lower saturation levels so felt must be dry. Defoamers may be used in the bitumen. c) Coating i) Composition This provides the continuos roofing layer and the backing of the roll. It provides not only the weathering and water resistance required but also binds the final granular material. The composition of the coating is a roofing bitumen like 90/18 or similar, often with stabilisers or polymer. The stabiliser adds to the mass of the coating reducing costs and creating reinforcement. It can also modify the binder characteristics increasing softening point and lowering pen. Polymers can increase elasticity and stiffness improving high and low temperature performance. ii) Granule retention To function the surface must retain the granular surfacing. This is a function of the viscosity of the binder at the time of application. The embedment must be sufficient to allow retention but not immersion of the granules. This will effect the look.. The granules must be compatible with the bitumen and clean and close to a single gradation. iii) Backing As the product is taken up in rolls it is important that the backing is not so sticky as to adhere to the granular surface. This is ensured by addition of talcs or backing papers. d) Cooling After complete formation to avoid marring of the surface the composite is cooled and rolled. The cooling is done on drums and the loopers. Air and sometimes water are used. excess water can cause stripping of the granules or blister formation. Overcooling can cause cracking during rolling or aggregate loss. Insufficient cooling can cause loss of pattern if embossing has been used. Temperature at rolling should be less than 50C. e) Shingles These are cut from roll materials and are intended to be laid in roofs in overlapping courses. Often shingles can have metal backings or be coated onto metal plates. 4.1.3.2 Performance of Prepared Roofing The performance of the in place roofing depends on: - granule retention a) Granule retention Initial retention and embedment in manufacture are not enough to ensure success. Contributors to retention are: - durability of the overall roof b) Cracking Resistance Surface crazing caused by oxidation, rupture due to shrinkage or weathering can open up cracks that allow water into the roofing causing swelling and further cracking. This first occurs in the coating and then spreads into the plies. It is caused by excessive oil in the binder. aging or fatigue cracking in flexible roofs. If coatings are too thick or stiff fatigue cracking will occur . Cracks may also reflect from below . It is important that cracks or joints in the roof are sealed with an elastic sealer before roof application. Polymer modified coatings will vastly improve these properties. c) Impact resistance Hail, damage caused during application or by traffic can crack the surface, particularly aged ones or where temperature is very low. Low fraas point materials , particularly polymer modified ones will perform better in this area. d) Blister Resistance. Blistering is caused by: - too high a voids content caused by foaming or poor application e) Wind Resistance exposure of edges to wind can cause lifting. f) Deformation Curling and clawing of shingles can occur due to inadequate backing thickness. g) Stain Resistance. The final coating should have self cleaning properties. 4.1.3.3 Application a) Roll Roofing This is applied by adhering the roll to the roofing substrate. The roof must be clean dry and free from grease or other extraneous matter. The rolls are applied by - torching a propane gas torch is used to tack up the backing and the roll smoothed out. - adhesives cutback or emulsion adhesives are rolled on and the roofing laid into it. - self adhesion The backing coating of the roll contains resins, oils or other tackifiers with a backing sheet. The backing sheet is removes and the roll spread. Adhesives are used to seal the seams. b) Shingles Sheets of prepared roofing are nailed with galvanised roofing nails in an overlapping pattern. In some instances wire or adhesives may be used. Shingles allow an overlapping pattern and so are useful on pitched roofs. Seams are usually sealed with adhesive or overlapped. 4.2 Protective Coatings Protective coatings of industrial bitumens have been widely used. Some of the more important areas have been: - Pipe Coatings 4.2.1 Pipes Application to pipes have included: - paper/ bitumen piping This is bitumen coated paper wound around a cylinder and cemented with industrial bitumen. Such materials have found uses in electrical conduits for cables or wires. - Pipe coatings. Metal pipes dipped, extrusion coated or wrapped with bituminised fabric or paper. Clay emulsions, hot bitumen and cutbacks have been used. This type is of most importance. Three systems have been extensively used: - hot applied mastic i) Hot Applied mastic This is composed of a graded aggregate ( sand or limestone), fibres and is bound with a bitumen like a 90/18. Polymer modification is an option. The aggregate grading is determined by the required thickness. For coatings of < 5mm top size is about <2.36mm, 3.5mm, for > 5mm . The pipe is first primed with a bitumen based cutback primer. The mastic is mixed in a pugmill and extruded on to the pipe. The thickness of the pipe coating varies from 1 to 2mm depending on pipe diameter. This is increased to 2.5-7.5mm when the pipe is to immersed in water. Very high softening point and low pen binders are preferred. The primer system must be rapid drying and low viscosity and based on the same bitumen as the pipe coating. ii) Cutbacks and emulsions. Fibre modified cutbacks or clay emulsions may be painted directly on to the pipe surfaces. Such coatings , while widely used have not been as effective as hot applied. This is due to solvent or water retention. However retained solvent does assist in weathering resistance and these coatings are useful for above ground work. Cutbacks are 70% solids, with 22% being filler and the solvent being a naptha cut. The emulsions are high solids clay emulsions. iii) Hot Applied enamels/ primers This is the most effective coatings. The low viscosity primer allows good wetting and penetration into pits in the metal surface. Durability is enhanced by windings of glass matt or fibres. The pipes are first primed by a dilute coat of primer then a full strength coat, taking care to allow each layer to dry then the enamel and coating material applied. The enamel is applied in multiple layers to 1-3mm thick by spraying . Bitumen must be 100-120C softening point and the materials are filled to about 25%. These enamels are heated for use and must not sag when applied. 4.2.2 Chemical and water Resistant Coatings. The chemical and water resistance of bitumen are closely linked. The resistance is related to low permeability and reactivity with any water based solution of chemicals, especially acids and alkalies. Resistant coatings can be applied in the form of clay emulsions, cutback , or hot applied. Testing is carried out with dilute or concentrated solutions of the chemicals required. Where the coating is used as a vapour barrier a permeability test is required, 0.5 perms or equivalent ( 0.5 grains/ft2/1" hg). 4.3.3 Paints. Paints based on solvents and industrial bitumens have wide use. They may contain vegetable drying oils, mineral fillers and pigments or aluminium paste. These paints can be lacquers or varnishes. A lacquer hardens solely by drying but a varnish will continue to harden after evaporation due to aging of the vegetable oil. The composition of such materials are 356-60-% 90/18 or harder grade in volatile solvent. Aluminium paints for metals are 17-30% bitumen, 37-58% solvent and 20-28% of a paste of aluminium powder at 65-75% solids). 4.2.4 Caulking Materials that are based on softer industrial bitumens with fillers , fibres, drying oils and rosins. Active fillers such as lime are often used. Rubber may be added to improve performance. Mastiseal 1517 is useful as a base for such compounds or used alone. 4.2.5 Fishnet Coating This material also has a special application for fishnets. A suitable formulation is industrial bitumen in an aromatic solvent is applied to the net by soaking in a vat. This allows penetration into the net fibres. The coating will not only improve abrasion resistance, resistance to salt but can be combined with herbicides to prevent growth of algae. 4.2.6 Rustproofing/ Sound Deadening. Rust proofing coatings may be based on cutback or emulsions of bitumen. Impermeability to water protects from corrosion. High softening point bitumen filled with inorganic or polymeric materials are effective sound deadening coatings. Fillers include silica, sand, clays aggregates and other bulking materials. They may be used on automotive or building applications. Clay emulsions filled with rubber particles are also effective in this application. 4.3 Building Applications. Common building applications are: - flooring 4.3.1 Flooring Flooring asphalts have taken several forms including: - mastic a) Mastic Stable bitumen emulsions can be blended with sand and or fibres or limestone dust to produce flooring mastic. These are used for floor levelling or crackfilling. A typical formulation that can be prebelended is: 1 part water The mastic is applied by spreading or heavy spray and trowelled to an even surface. Drying is 36-48 hours. A curing coat or dampening is required to ensure no cracking . This is useful for commercial or factory flooring and is topped with a thin aggregate coat. b) Felts. These are basically obsolete but were used until the 60's as an alternative to linoleum. A saturated felt backed by hessian is surfaced with a thin layer of hard bitumen (135/7) embossed or finished with a printed colour pattern. Wood pulp felt or synthetic woven fabric is suitable. tensile strength of the flooring is improved by polymer modification such as SBS, APP, neoprene or SBR. A coating of starch on the backing makes removal and replacement easier. c) Abrasive Coatings. these are materials designed specifically for non slip flooring. The flooring is applied as for standard flooring but a gritty material is spread on the surface. Crushed sand and silica are suitable over a clay emulsion such as Emastak. d) Waterproofing and damp proofing Membranes. The materials used in these too functions are the same. they vary only in degree. Such materials are applied directly or as membranes to building foundations or areas below ground. They are often used to line trenches or electrical conduits. The materials are applied hot or as clay emulsions. When in membrane form the binders are coated on to cotton glass or polyester fabrics and adhered to walls or floor using mopping bitumens or adhesives similar to roofing applications. Multiple plies are applied with hot bitumen at 175-300C ( depending on the grade) over the top. e) Papers Bitumen treated papers were used as waterproofing protection for storage and transport of equipment. Polymer films have made this obsolete. 4.3.2 Insulation The main applications are: - siding i) Siding These are similar to shingles and used to protect the sidewalls of buildings. They are constructed of materials similar to shingles. ii) Plasterboard/ Fibreboard Bitumen may be used as an insulating and adhesive medium. The board may be fibre, plaster or simply chipboard coated on one side with bitumen. The bitumen also renders the board waterproof.This is analogous to the use of wax or wax emulsions in this application. Suitable bitumens are 70-115C RBSP and 3-7 pen. For clay emulsions a 40-50pen bitumen is used. iii) Acoustical Blocks These are saturated felt made similarly to siding but with a winding pattern to allow gaps or channels. They are then adhered to fibre board . This laid between walls or under floor boards. iv) Electrical Polymers have made most electrical applications obsolete but the good resistivity of bitumen meant that it could be used for wire coating, electric conduits and even insulating tapes. PVC has replaced it . 4.4 Other Other interesting applications include: - automotive 4.4.1 Automotive - panel board a) Panel Board Filled 90/18 bitumen with fibres and inorganic fillers are extruded onto boards for sound deadening. Often there is no substrate and the bitumen is applied and baked into place . The flow takes up the panel shape and the bulk provides relief from noise, and vibration. b) Floor deadener Felt impregnated with bitumen and bulky fillers such as rubber are used in floor panels for vibration and noise reduction. c) Acoustic felts. Flexible impregnated felts have been used for lining hoods and trunks. The high softening point resists heat. 4.4.2 Batteries These include - battery box compounds a) Battery Boxes hard bitumen was used for many years for battery boxes due to its high acid resistance. It was a mix of cotton fibre, pyrites and very hard bitumen. First polymers then rubber superseded this. b) Storage or Wet batteries. In reclaiming batteries bitumen is used extensively for sealing cell covers.. The sealer must provide a bubble free seal, adhere to the rubber or polymer cover, be acid resistant and withstand internal battery pressure. Sealing compounds of 80-125 RBSP and 30-40 pen are suitable. Catalyst blown bitumen often gives best results as the final materials are more crack resistant. c) Dry Cell Sealing. The bitumen sealant is placed above the acid/oxide paste. Products must combine pliability, inertness, and non conductivity. 80-95C RBSP and 150-25 pen bitumens are required. d) Other Bitumen has been used for capacitor seals, transformer potting and coil impregnation. 4.4.3 Briquetting Finely divided fuels can be upgraded into briquettes by binder with a suitable bitumen. It is useful for sawdust, peat, coal dust, brown coal and shale. Metallurgical brachiates based on coke can also be made this way. materials used have included hard bitumen, penetration bitumens and emulsions. The binder and the fuel are mixed and then pressed between rollers to form the brachiates.. The following steps are taken. a) The fuel is dried to give about 2% moisture. b) The material is crushed and oversized eliminated ( this would make the briquettes non cohesive). c) Mixing or fluxing is carried out in a pugmill. Binder is added to the dry components as emulsion, foamed bitumen or hot binder. Mix temperature is kept to about 75C for 55-60C RBSP and 85C for 60-70C . d) The mix is pressed at about 65C. Much higher and the briquette will be brittle and too low the briquette will be low density. e) cooling The briquettes are cooled to below softening point. With the right coal and binder content that low smoke high strength briquettes can be made. 4.4.4 Printing Inks Newspaper and other printing inks are made from bitumen. It is a fast ink- wont cover fingers! 90/18 is used with highly evaporative solvents and vegetable drying oils such as soya oil. 5. CONCLUSIONS Bitumen is a very useful industrial material. It is economic and reliable. The functions that bitumen performs are binding coating , impregnating waterproofing, insulating and covering. The required balance of properties depends on the function to be employed. Manipulation of properties is possible by manufacturing method, polymer modification or by use of fillers and fibres. The technologist must master the rheological requirements and match this to the application the most economic way. |
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TECHNICAL NOTES 