Shell Bitumen

The Shell Bitumen Handbook, Shell Bitumen, Chertsey, Surrey, UK, 1990. 

Figure 3.2 Schematic representation of the anaiysis for broad chemical composition of bitumen. (From Shell Bitumen, The Shell Bitumen Handbook. Surrey, UK Shell Bitumen UK, 1990.)...

The observed change in bitumen composition during distillation and air-blowing is demonstrated in Shell Bitumen (2003). 

The same figure also presents the effect of temperature on the emulsion viscosity. As the temperature is reduced, the emulsion viscosity increases. This increase is more distinct to emulsions having a bitumen content of more than 65%. Moreover, the emulsion viscosity is affected by the bitumen viscosity during emulsification, the acidity of the aqueous solution and the emulsifier content (Shell Bitumen 2003). When the viscosity of the bitumen entering the colloid mill is reduced, the average diameter of particles is reduced and the emulsion viscosity slightly increases. Additionally, a relative increase of the viscosity is observed when the acidity of the aqueous solution is reduced and emulsifier content is increased. 

For a given compatible system, the quality of polymer dispersion achieved is also influenced by the concentration of the polymer and the shear rate applied by the mixer (Shell Bitumen 2003). 

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. 

Finally, during compaction, the bitumen should also have an appropriate viscosity, so that effective compaction is ensured. If the viscosity is too high, the bituminous mixture cannot be compacted properly. If the viscosity of the bitumen is too low, the bituminous mixture becomes too soft that it cannot sustain the dead load of the roller and compaction is delayed. It is widely recognised that the optimal bitumen viscosity for compaction is between 2 and 20 Pa-s (Shell Bitumen 2003). 

A variety of vapours and fumes are emitted during handling bitumens at elevated temperatures. Visible emissions or fumes normally start to develop at approximately 150°C and the amount of fume generated doubles for each 10°C to 12°C increase in temperature (Shell Bitumen 2003). 

Under conditions of high temperature and in the presence of oxygen, an exothermic reaction can occur, leading to the risk of fire or explosion of the tanks. Flence, manholes in bitumen tanks should be kept closed and access to tank roofs should be restricted (Shell Bitumen 2003). 

The hazards associated with skin contact of bitumens other than burns are negligible. Flowever, cut-back bitumens and bituminous emulsions, because they are handled at lower temperatures, increase the chance of skin contact. Studies carried out by Shell demonstrated that the bitumen is unlikely to penetrate the skin and the bitumens diluted with solvents are unlikely to present a carcinogenic risk. Nevertheless, bituminous emulsions can cause irritation to the skin and eyes and can produce allergic responses in some individuals (Shell Bitumen 2003). 

LCA covers the entire life cycle including extraction of the raw material, manufacturing, transport and distribution, product use, service and maintenance, and disposal (recycling, incineration or landfill). LCA can be divided into two distinct parts, the life cycle inventory (LCI) and life cycle impact (Shell Bitumen 2003). 

Shell Bitumen. 2003. The Shell Bitumen Handbook, 5th Edition. London Thomas Telford Publishing for Shell Bimmen. 

Van Gooswilligen G. and W.C. Vonk. 1986. The Role of Bitumen in Blends with Thermoplastic Rubbers for Roofing Applications. Thermoplastic Rubbers Technical Manual TR 8.16. Chertsey, Surrey, UK Shell Bitumen, UK. 

Today, the use of the sliding plate viscometer is very limited and mainly for comparative studies with other viscometers. For further information, see Griffin et al. (1957) and Shell Bitumen (2003). 

The stiffness modulus is also affected when the grade of bitumen and its penetration index change. This has been demonstrated in Shell Bitumen (1990, 2003). 

The strength of bitumen, and of many other materials, is reduced by repeated loading. A study contacted by Heukelom on the tensile strength of bitumen proved that the bitumen s resistance to fatigue is solely dependent on its stiffness. From the nomograph developed, the fatigue strength of the bitumen may be determined by each stiffness value (Heukelom 1966 Shell Bitumen 2003). 

Figure 7.14 Nomograph for evaluating the stiffness modulus of asphalts. (From Bonnaure F. et al., A new method of predicting the stiffness of asphalt paving mixtures. Proceedings of the Association of Asphalt Paving Technologists, Vol. 46, p. 66, 1977 Taken from Shell Bitumen, The Shell Bitumen Handbook, Chertsey, Surry, UK Shell Bitumen UK, 1990.)...

The simplest test used to study the deformation behaviour of asphalts was the static unconfined uniaxial compression test, termed the creep test, developed in the 1970s by Shell Bitumen (Hill 1973). The specimen was subjected to static axial compressive load over a long period (1 h). The test procedure was very simple and required low-cost equipment. In addition. Shell Bitumen developed a rut prediction procedure based on results of the creep test but soon realised that it underestimated rut depths measured in trial pavements (Hill et al. 1974). This was attributed to the effects of dynamic loading producing higher deformation in the wheel-tracking test (Van de Loo 1974). 

Shell Bitumen. 1990. The Shell Bitumen Handbook. Chertsey, Surry, UK Shell Bitumen UK. 

Source Shell Bitumen, 7he Shelf Bitumen Honc/book.Surrey, UK Shell Bitumen UK, 1990. 

Shell Bitumen Handbook. 2003. London TTL. Its association with a single company is misleading regarding the coverage of this handbook, which is a valuable up-to-date source on the use of bitumen. 

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