A physiochemical study of the heating of low cement castable refractories and the problem of explosive spalling.
Low cement castable (LCC) refractory linings, over recent years, have superseded
refractory bricks in many high temperature applications. There are concerns however,
pertaining to their dry-out. In particular the catastrophic destruction of LCC shapes or
linings as a result of phenomenate rmede xplosives palling.
This thesis describes the study of both the on-site treatments of LCCs and the
physicochemical changes that occur during heating. Two types of explosive spalling event
are classified,b asedo n on-siteo bservationsa ndp ost-mortems tudy.
A model is presented that describes the physicochemical changes in a LCC system as it is
heated from ambient to 450°C. From this model a zone of high vulnerability to explosion
has been identified between 230-280°C. The dehydration of the hydrated alumina phase
gibbsite (AH3), within this zone, is identified as a possible cause of explosive spalling.
An investigation of polypropylene fibres, which are added to LCCs as anti-explosion
additives, found that the fibres block porosity between1 60-240°CI.t is suggested that this
additive system is not optimised and that polymer fibre blends may be more advantageous.
The diffusion characteristics of a LCC system cured at 5 and 20°C is presented. It was
found that at the lower curing temperature the diffusion rate was lower. This supports the
recommendation for the use of high curing temperature to facilitate the drying of LCCs and
reduce the risk of explosive spalling.
A list of guidelines that could be used to establish benchmark standards for the
development of best practice in industry has been compiled from the results of these