During the past 40 years in the refractory industry, I have seen and been part of the continuing effort to develop monolithic refractories as the go-to product for most heat-intensive industries. However, there are still applications where brick is a better choice.
During my “early years” on the Onex construction team, 100# bags of castable containing plenty of cement was the car deck refractory choice of the day. A mortar mixing tub and a cement hoe were “good enough” because the “liberal” water use made mixing easy. A quick hit with a pencil vibrator, and off you went. We called them “utility castable” in those days.
After the 1980’s recession, castable and other monolithics such as plastic ram and dry vibes became even more critical. Because the tradesmen programs run by big steel companies faded away, installing refractories needed to be made simpler for the semi-skilled worker in the mill. Mix it, dump it, or ram it.
Castable Refractory Products
Over the years, product improvement efforts have revolved around improving castable products’ properties. Close attention is paid to particle sizing, raw material sourcing, and cement content/quality. These changes have led to increased product densities, increased hot and cold modulus of rupture (MOR), higher abrasion resistance, higher temperature performance. Now, these products are closer to the properties of pressed and fired brick shapes.
It is important to note that castable properties look great on a datasheet. Still, the variables associated with casting, such as weather conditions, water content, mixing time, vibration time, air curing, and final firing, can have a marked effect on your actual finished properties and performance. Too cold, too much/too little water, not vibrated correctly, not cured and appropriately fired, or not mixed long enough can lead to substandard properties, not those stated on the data sheet.
Brick Is The Best Choice Sometimes
Even with the great strides, the monolithic manufacturers have made, there is still a place for brick. It would be best if you did not overlook the advantages of using a brick product that has been mechanically pressed and high fired. It has the properties as indicated on a datasheet. And in those tougher/troublesome applications or when installing a castable is not possible, brick may be the best choice.
Sure, the use of brick will require the need for skilled tradesmen (masons). But when installed correctly, the refractory brick can help you keep equipment up and running any time of the year. Brick products are available in many chemistries for many applications and numerous shapes to fit a specific area or diameter. When to consider refractory brick as part of your maintenance program:
- During colder times of the year when the casting environment is not ideal.
- As a Just-In-Time (JIT) material available on site that doesn’t have a shelf life issue.
- Need a product that is not susceptible to negative material property deviations that have the potential to occur during the casting process.
- The furnace lacks the abilities to properly cure and fire castable material in a slow and controlled manner.
- Movement of the castable to the area requiring repairs is difficult or impossible.
- A composite lining makes sense, such as an insulating firebrick sub-hearth and cast hearth.
- You’ve tried every castable you can to no avail.
Brick should be part of any plant’s refractory maintenance planning and design consideration (in addition to castable, plastic ram, and dry vibe). A professionally installed brick lining could be the answer to some incredibly challenging applications.
Give brick some consideration when you talk to your supplier about your problem areas’ best refractory design. And don’t forget, the mortar used with the brick is critical, so don’t go cheap. Utilize a mortar that complements, or exceeds, the chemistry of the brick.