TLA stands for Trinidad Lake Asphalt which is one kind of natural bitumen deposits with relatively higher ash content and less bitumen content, mostly found in form of pitch lakes. Most famous Lake asphalt in the world is Trinidad Lake asphalt while deposits have been found in other countries including Iran. Unlike Gilsonite which has a wide range of applications, TLA has been found useful only in Pavement applications to mix with Penetration Bitumen to increase pavement qualities. This has caused international use of Lake asphalt in Bridges and Airport Runway pavements.
TLA natural characteristics provide an economical chance for blending with Hot Bitumen without further temperature insertion. The practice is based the softening point of TLA to be less than the softening point of the Hot Mix.
TLA exploitation is a Monopoly in Trinidad and Tobacco in the name of Lake Asphalt of Trinidad and Tobago limited and the rumor is ownership of this company belongs to American Entities providing an international sales network with enough control Not to affect the current Gilsonite market in the pavement sector.
Difference between Gilsonite and TLA
Difference between Gilsonite and TLA is by Nature. While both materials have originated from Crude Oil, the molecular structure are very different resulting in a very different specification. In the below table you can find a comparison between Gilsonite from 3 origins (Iran, Uzbekistan and USA) with 2 Lake asphalts (Iran and Trinidad):
For improving pavement characteristics, including strength, longevity and binding, the natural bitumen must be added to a penetration bitumen grade such as 60/70 or 40-50. Gilsonite Vs TLA needs less percentage of addition from 5-10% while TLA has to be mixed up to 30%. While low softening point of TLA makes an easier blending into the hot mix, Gilsonite high softening point requires the blender to apply a higher temperature to the mix in order to melt the Gilsonite fully.
In addition, lower ash content of Gilsonite provides a better resistance to cracking comparing to TLA. He high ash content of TLA will act as non-bituminous aggregate unless filtered. Therefore, Gilsonite Vs TLA has a better cracking resistance.
Another comparison aspect could be content of Bitumen. Gilsonite suitable for asphalt binder has minimum 90% Solubility in TCE (Bitumen content) while TLA bitumen content is below 60%. Therefore, the binding strength of the two materials have different effect on the courses of asphalt.
The basic advantage of TLA Vs Gilsonite is price. TLA costs roughly around penetration bitumen price delivered to most destinations while American Gilsonite is twice the Penetration Bitumen prices. Using high quality Iran Gilsonite could improve the economics, but still more expensive than TLA prices.
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