Coloured bitumen

Coloured or pigmentable bitumens are those whose colour is different from black, and when mixed with aggregates, the pavement s surface is coloured. 

The majority of coloured bitumens are produced by the addition of a pigment during mixing process with aggregates. The most common pigment used is the iron oxide, which results 

The disadvantages of coloured bitumens/asphalts are as follows (a) steep price owing to the high cost of the pigment and (b) the fact that the only truly stable colour that can be achieved is red, which, depending on the traffic, type of asphalt and ambient temperatures, gets dirty (due to rubber tyre traces left on the surface). 

Over the last few years, the industry has developed synthetic binders that can be coloured in any colour with relatively less cost. Synthetic bitumens have almost the same properties as common paving bitumens. More information can be found in Shell Bitumen (2003) and the Web. 

To preserve the colour on the pavement s surface, it is recommended that aggregates of the same colour as that of the pigmentable bitumen be used. 

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The bitumens have a good order of chemical corrosion resistance, have reasonably good electrical insulation properties and are very cheap. Their main disadvantages are their black colour and their somewhat brittle nature. 

The semi-fuse thus produced is waterproofed by passing through troughs of molten bitumen or by coating also with plastic.For higher grade safety fuse, a further countering of textile, such as cotton, is followed by a final varnish, which may be coloured for identification purposes. 

Like the natural iron oxide pigments, the synthetics are used for colouring concrete, bitumen, asphalt, tiles, bricks, ceramics and glass. They are also used extensively in house and marine paints. Because the shapes of the particles can be accurately controlled and the particle size distribution is narrow, synthetic iron oxides have a greater tinting strength than the natural ones and so, are chosen where paint colour is important, i. e., for top coats. Red iron oxides are used in primers for automobiles and steel structures. 

Factis is, however, often sold mixed with various extraneous matters such as mineral substances, mineral oils, vaseline, or paraffin wax, resins or resin oils, bitumen, tar, etc. Further, white factis may be coloured artificially by organic colouring matters soluble in fats. 

Rubber is vulcanised by treatment with sulphur chloride or by heating with sulphur. In most cases, however, rubber articles are made, not of pure vulcanised rubber, but of the latter mixed with various other substances, organic and inorganic. The organic substances more commonly used are brown and white factis, fatty oils, oxidised oils, waxes, mineral oils, paraffin wax or ceresine, resin or resin oils, bitumens, tar, pitch, starch, and artificial dyes. Very many inorganic compounds may be added either as fillers or to give colour, e.g., talc, kaolin, asbestos, chalk, gypsum, lime. 

The extraction is finished when the thimble holding the substance loses its brown colour and becomes completely decolorised, this requiring 1-2 hours. Excessively long extraction is to be avoided, since an appreciable part of the rubber would then be dissolved. The pyridine solution is evaporated in a tared porcelain dish on an oil-bath, the residue representing the bitumen, tar and pitch of the original substance. 

Bitumen. Bitumen is a black thermoplastic obtainable from the refining of crude oil. Its composition is somewhat variable, depending upon the type of crude, and it tends to stain light-coloured substrates. However, the relatively low cost of the material makes it attractive for some applications and it may be compounded with other thermoplastics—like the polyolefins. 

Rouelle downplayed the role of theory while he promised a great, sensational show. The last part of his course would reveal the substances that are taken from the entrails of the earth and would be the object of unusual experiments on bitumen, niter, marine salts, and the acids. The effects of all the mixtures would produce changes in colour, detonations and the production of flames ... 

Shales are fine grained, clay-like rock structures that cleave readily into thin layers. Many shales are coloured black on account of the bitumen that they contain. There are also gas shales in which considerable quantities of natural... 

Resins have similar components to asphaltenes but they are soluble in w-heptane. They are solid or semi-solid, dark brown in colour and strongly adhesive. Resins are dispersing agents to asphaltenes and their proportion to asphaltenes control the gel/sol type of character of bitumen. Their molecular weight is lower than asphaltenes. 

Aromatics are naphthenic aromatic hydrocarbons, have the lowest molecular weight of the compounds in the bitumen and represent the main dispersion medium of asphaltenes. They are viscous fluids of dark brown colour and they can be found at 40% to 65% in bitumen. 

Saturates are aliphatic hydrocarbons together with alkyl naphthenes and alkyl aromatics. Their molecular weight is similar to the molecular weight of aromatics and their components contain both waxy and non-waxy saturates. Saturates are light yellow to white in colour and its content ranges from 5% to 20% in bitumens. 

All trays are left for a sufficient time (approximately 20 to 45 min, depending on the bitumen emulsion) until the surface colour changes from brown to black (breakdown of bitumen emulsion occurs). 

The medical literature has sparse reports. Excessive environmental heat in a Nigerian battery manufacturers induced sweating and maceration of the skin, especially over the anterior abdominal wall this predisposed five individuals wearing dark-coloured uniforms to clothing dermatitis. In the same report, one person working with bitumen developed an acneiform skin eruption (Olumide et al. 1983). 

The appearance of black roads with white lines is suitable for the purpose of detailing several areas of the road. Despite this fact, in some situations the colour of traditional bitumen is not suitable due to security or aesthetic reasons. The most common causes for modifying the colour of synthetic binders are to ... 

Bitumen which besides facilitating the colouration, provides the necessary mechanical properties of load resistance typical of bitumen. 

Bitumen which is only a means of adhesion and application of colour, while a bituminous asphalt base maintains the mechanical properties. 

As mentioned previously, the difficulties in obtaining colourable blends from bitumen mixtures have forced the research and production of synthetic substances which are easily colourable, with mechanical properties similar to those of bitumen, allowing their use in most applications where coloured mixtures are advised. These products, known as binders or light synthetic binders, because of their light tones, are a mixture of substances that form a macroscopically compatible system. The colouring is easy and with 1-2% w/w pigment, colour shades are obtained which meet most of the desired colour range [5]. 

Rivington (1901) lists Indestructible Paint which he says is available in three colours (bronze-green, chocolate and black) as enamel paints, made from zinc oxides or lead oxides groimd with oil and petrolemn spirit, with bitumen added. These paints were useful for painting industrial surfaces subject to the attack of steams, acids and alkalis or to the fumes of gas and produced a hard, washable surface. Rivington goes on to discuss bituminous paints in some detail. They are made fiom vegetable bitumen, asphalte and mineral pitches dissolved in paraffin, petroleum or... 

A humic earth, typically associated with the so-called Vandyke brown (qq.v.). Salter (1869), for example, describes it as an earth containing bitumen. .. [d]eposited at the bottom of seas, lakes, or rivers, and subsequently covered up by the accumulations of clay and sand, the organic tissue undergoes a kind of fermentation by which the bodies in question are slowly produced. It could also be calcined to give a darker colour. 

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