Natural asphalts as additives

Natural asphalts such as Trinidad asphalt, rock asphalt or gilsonite are blended with bitumen derived from crude petroleum in order to improve its properties. Since the above additives have very low penetration and very high softening point, the resulting bitumen becomes harder. Since the chemical composition of the natural asphalt is similar to the bitumen from crude petroleum, performing the blending procedure is far easier and homogeneity of the final modified bitumen is ensured. 

Because of its chemical composition, TLA is considered as a thermoplastic material. Apart from hardening the bitumen and making it less temperature susceptible, the addition of TLA to petroleum bitumen improves the asphalt s durability, stability, stiffness, anti-rutting performance and fatigue characteristics. TLA is available in semi-solid state or in pellets. Recently, a new product, in pellet form, was introduced and was found to be suitable for warm asphalt mixtures (Lake Asphalt of Trinidad and Tobago Ltd 2014). 

The proportion blended with the petroleum binder varies and depends on the original bitumen and the desired final properties. With regard to pellets, the appropriate proportions range from 25% to 40%, by mass of bitumen. 

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