The low relative permeability of advanced castables and the difficulty or increased care in baking out field installations has led to the widespread and almost universal use of organic bake-out fibers (OBOF) to increase permeability and aid in water release especially in the critical dehydration range.
Figure 3 illustrates the trend of low permeability of a low-cement castable and the increase achieved by the use of an OBOF addition versus the normal permeability of a conventional dense castable.