With the right chemical additives/rejuvenators 100% RAP mixes are actually possible to make in just about any plant. Temperature control is key to minimize emissions and further degradation of the binder (oil). Then it’s making sure feeders and chutes can handle the volume, the baghouse is doing its job at lower temperatures, and the plant can run slow enough to get the RAP to temperature with a smaller flame (low and slow...BBQ anyone?).

After that comes fractionating the RAP into five sizes, rather than the one or two necessary at lower percentages and testing testing and more testing so you know the oil content and binder grade of each size of RAP. This reduces the likelihood of wild swings in finished oil content and grade. So far we’ve only made it to 50% for hot-mix (permit limit) but have run 100% RAP for cold mix.

Like I saw down below, it’s a royal pain for the operators and as such, not really viable for a large scale operation. The cool thing is as rock sources become more limited and oil more expensive, the break even on developing new chemicals and processes that increase viability start to make more sense.