Most guidelines for SMA do not recommend producing large quantities of a mixture and holding it in reserve for too long for future use. SMA stockpiling is an uncertain business due to the risk of binder draindown when storing hot mixture. Such limitations cause problems when the asphalt plant has a low output and large amounts of mixture are needed to be supplied to a laydown site. It can be assumed that, depending on the temperature, mineral composition, and binder content, the mixture may be stored for up to 2 or 3 hours at a high temperature. The risk of draindown is magnified by the SMA’s extended storage time in a silo, which is why it should be sent to the work site within a reasonable amount of time after production.
It is important to monitor the decreasing temperature of a mixture in a silo. Not every silo is equipped with heated walls or even a heated chute. Allowing the mix to cool substantially in the silo may cause many problems, especially with a polymer — modified binder. It has been stated in the U. S. Department of Air Force guidelines (ETL 04-8) that a ready-made SMA mixture can be stored for no longer than 1 hour in uninsulated silos or 4 hours in thermally insulated silos. If, for any reason, the hot SMA has to be stored longer in a silo, then it is worthwhile to incorporate a higher amount of stabilizer.
