Description
The South African Roads Industry is aware of the success achieved with bitumen rubber over the last 25 years. Due to its visco-elastic behaviour, the binder requires elevated temperatures to handle the product in sprayed seal and asphalt applications. The experience by the roads industry of the rapid deterioration of bitumen rubber when handled at high temperatures during sprayed seal applications created perceptions regarding the use of bitumen rubber in asphalt applications. One of the perceived drawbacks of bitumen rubber in asphalt application is its limited shelf-life. While investigating flushing problems during the construction of the bitumen rubber asphalt semi open (BRASO), it was implicated that these problems may have been as a result of binder degradation associated with the limited shelf-life of the binder at high temperatures. The bitumen rubber suppliers and asphalt manufacturers were requested to conduct shelf-life studies to duplicate the bitumen rubber binder’s time-temperature profiles at various scales of operation. The shelf-life studies included laboratory blends with two different grades of base binder and static and dynamic storage tests. The laboratory study was also repeated on a large scale, manufacturing bitumen rubber through a sprayer unit. The properties of the product were monitored over a twelve hour period and the asphalt properties of the aged binder at different stages of ageing were tested to assess the impact of binder ageing on the BRASO behaviour. These studies revealed important facts that are often misunderstood. In this paper, the misperceptions of bitumen rubber shelf-life are addressed and the effect of the base binder, the scale of operations and the storage stability will be contextualised indicating a much improved actual shelf-life in asphalt cement relative to the current 4-6 hours allowed.
