2 Bituminous MaterialsThe term bitumen is a generic name applied to various mixtures of hydrocarbonsThey may be gaseous, liquid, semisolid, or solidMost common materials within the family of bitumen’s are tars, pitches, and asphaltsDestructive distillation is carried out on natural materials produces tarPartial evaporation or fractional distillation of tar produces the solid or semi-solid residue of pitchAsphalts are dark brown or black solids or semi solids which are found in the natural state and are also produced by the refining of petroleumSome natural deposits of asphalts are found in Kentucky, Utah, Colorado, and California95% of asphalt materials used in North America are derived from the refining of petroleum
3 Test of Flow of Properties The viscous or flow properties of bitumen’s are of importance, both at the high temperatures encountered in processing and application and at the low temperatures to which bitumen’s are subjected in service. Flow properties are complex, and as a result, tests have been formulated to measure the consistency of the materials at temperatures comparable to those encountered during the service life of the bitumen.
4 Test of Flow of Properties The penetration testMeasures the depth of penetration in tenths of millimeters of a weight needle into a bitumen during a period of time at a given temp.Softening point testMeasures the temperature degrees Celsius at which a steel ball falls a known distance through the bitumenDuctility TestAre conducted to determine the amount a bitumen will stretch at temperatures below its softening pointViscosity TestsAre used to determine the flow characteristics of asphalts in the range of temperatures used during applicationFlash Point TestIndicates the temperature to which asphalt cement can be safely heated without danger of flash. A brass cup is partially filled with cement and heated at a prescribed rate. A small flame is place over the surface of the sampleThin Film Oven TestTest is used to obtain a general indication of the amount of hardening which may be expected to occur in an asphalt cement during the plant operation.Viscosity TestPenetration Test
5 Types of Bitumen’s Tar and Pitch Most of the tar and pitch used in construction is made by the distillation of coal.Tar is used to saturate felt paper and coated kraft paper to produce a waterproof membrane.Coal – tar pitch oxidizes quite rapidly when exposed to ultra violet rays of the sun.
6 Types of Bitumen’s Asphalt A large percentage of the asphalt used results from the refining of crude oilsThere are three main groups of asphalt products produced from straight run asphalts
7 Asphalt Hot asphalt- those soften by heat Hot asphalt can be used directly or it can be processed further to produce a harder materialHot asphalts have good resistance to the transmission of water and water vapor when they are applied to dry surfaces and the heating process is controlledHot asphalts bond poorly to damp or wet surfaces, have relatively poor flexibility, oxidize under the sun’s rays and are brittle at low temperatures
8 Asphalt Cut back asphalts – those dissolved in mineral solvents Cutback asphalts are of three typesStraight run asphalt and solventHeavily filled cutback made by adding a large amount of filler and fiber to asphalt cut with solventPrimer type cutback asphalt in solution with no filler or fiber
9 AsphaltEmulsion asphalts – those dispensed or suspended in a water baseThree typesSoap type in which soap is used as the emulsfierClay modified soap type – clay and soap are used as emulsfierClay based typeAdvantagesEasy to handleAddition water is all that is necessary to decrease viscosityDrying involves the loss of water by evaporationNo heating is requiredGood bonding to damp or wet surfaces
10 Uses of Bitumen’s Waterproof coating and membranes Asphalt pavement Used to provide a waterproof coating for walls and to make waterproof membranes in buildingsAsphalt pavementAsphalt cutbacks and emulsions have their greatest use in road constructionAccounts for about 85% of amount produced in North AmericaAsphalts in pavements acts as a binder for the aggregates, in this capacity as a cement, the asphalts are usually semisolidBefore it can be mixed with the aggregate the asphalt must be made liquid by heating, and cutting with solvent or by emulsifying with water
11 Uses of Bitumen’s Liquid paving asphalts Most of the liquid asphalts used for paving are cutbacksThree typesGasoline used as a solvent rapid curing liquid asphaltKerosene – produces a medium curing asphaltHeavier fuel oils produce a slow curing asphaltTypes refer to the rate at which solvent is lost, either during construction or after pavement has been laidThe liquid asphalt to be selected for any given project depends on the construction conditionsIn general a rapid curing grade can be used as a binder for open graded aggregates that coat quickly during mixing or for surface treatmentsMedium curing grades are required for dense graded aggregates which require longer mixing timeSlow curing grades are used with aggregates requiring a long mixing time and for projects where the pavement may have to be torn up and reworked from time to time
12 Uses of Bitumen’s Asphalt paving cements The binders for the more expensive asphalt pavements are usually asphalt cementsThese semisolid materials are also separated into grades having different ranges of hardnessAsphalt canal liner and bank erosion controlThe versatility of asphalt has led to its employment in many types of hydraulic structuresMixes made with the harder asphalts
13 Uses of Bitumen’s Asphalt shingles Built up roofing Asphalt shingles are made from heavy rag felt, saturated with asphalt and coated with high melting point flexible asphaltCeramic coated mineral granules are pressed into the asphalt coating on the exposed face to provide a fire resistant surface.Built up roofingBuilt up roofing is term applied to a type of roofing made by building up successive layers of felt paper and asphalt over a solid roof deckFive typesType 1 – consists of asphalted felt paper, asphalt and gravel or slagType 2 – consists of tarred felt paper pitch and gravelType 3 – consists of asbestos felt, asphalt felt and a smooth flood coat of asphaltType 4- requires heavy slate surfaced roofing paper as well as asphalt saturated feltsType 5 – called cold process – felts are cold process felts saturated with cold asphalt emulsion and the asphalt top coating is applied cold.
14 Uses of Bitumen’s Rolled roofing Sprayed on asphalt roofing Rolled roofing consists of very heavy asphalt saturated felt paper, with or without finely crushed slate embedded in one surface put up in rolls.Sprayed on asphalt roofingA new technique for the application of asphalt roofing involves the use of special equipment for apply the materialA special gun with three nozzles and a fiber cutting chamber is usedGlass fibers are fed into the chamber where they are cut to predetermined lengths and blown out through a center nozzle
15 Uses of Bitumen’s Asphalt flooring Fiberboard Asphalt mastic flooring – is made by mixing an emulsifed asphalt with Portland cement, sand and gravel or crushed stone to form a plastic mixture. This is spread over the floor screened compacted and floated to a depth of ½ in.Asphalt tile – are composed of fibers bond together by a blend of selected asphalt bindersFiberboardInsulation boards composed of asphalt impregnated wood fibers used in built up roofing systems
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