21 May 2015
SCI's Construction Materials Group
SCI, London, UK
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Adrian Blacker is Managing Director of Asphalt Associates Limited, a company which trades internationally a variety of natural asphalt modifiers. He is an Incorporated Engineer and has been involved with highways and pavement construction for over 20 years.
For the last 10 years he has primarily been concerned with natural asphalts and their use in pavement engineering projects around the world. Adrian represents these materials on various committees in Europe and elsewhere. He is currently Chairman of the Bitumen Modifiers Association representing them on B510/19. Adrian is an editorial member of the Caribbean Construction Digest.
Natural asphalt has been used in international pavement construction for well over a hundred years. Although the role of such materials has changed, they still find a significant and growing market in the asphalt industry.
Many sources of natural asphalt have been exploited over the years and a little of the history of their use is described along with the location of the deposits. Perhaps the most famous natural asphalt products are; Trinidad Lake asphalt and Gilsonite and these will be discussed in a little more detail.
Although TLA shows many desirable traits, it also possesses some less desirable, such as difficult handling and high Relative Density. Despite this, the material is used on all types of asphalt pavement, including; long-span bridge deck surfacing, heavy duty applications, airports and racetracks. The deposit is easy to access and mine being a surface deposit. It is subjected to a relatively simple refining process before being packaged for export. A crushing operation in Germany further processes the material for the European market.
Gilsonite is somewhat different and is obtained from a series of well defined mineral vein deposits located 40 miles from vernal, in the north east corner of Utah. The material is mined largely by hand from difficult to access narrow veins. The material is believed to have originated from the Green River Formation of oil rich shales which underlay the Uintah Basin. Deep vertical fissures were once filled with heavy, viscous hydrocarbon which lost its volatile components over millions of years and solidified.
Production began in 1885 and many uses have been found around the world, which include; printing inks, asphalt modification and drilling lubricants. Although Gilsonite is very pure as found, the properties vary throughout the deposits. The mined material is therefore subjected to a processing operation which produces a number of products for the market which are subjected to rigorous quality control
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