Water Content – Small Change, Large Impact

Regardless of the installation method being deployed in order to successfully install refractory materials, generally speaking, monolithic refractory installations share one common step, the addition of water. Whether the water is added in a large paddle mixer prior to being vibration cast, pumped, or shot-creted, at a nozzle prior to being gunned, or in a pail prior to being hand cast, this step has wide-ranging impacts on several aspects of the end result.

The water content can easily be taken for granted. At times, it is tempting to add additional water relative to what is called for on a product’s mixing and use instructions in order to get the material to flow better, avoid voids, or extend the workability time. At other times, it can be seen as beneficial to reduce the water content with the intention of improving physical properties or expediting set times. While, the introduction of additional water is a far more common offense, in reality, introducing water to a refractory mix that is outside the parameters set by the material manufacturer can have the following detrimental impacts on the finished products:

1. Reduction in physical properties – Improper water content leads to a reduction in the physical properties associated with a monolithic refractory material. This can decrease the lifespan of the refractories as well as create issues for the end user throughout the time period in which they are in use. In many cases, end users select more costly refractories in order to acquire higher quality materials. The improper addition of water can completely negate this additional spend. In many cases leading to performance, that is inferior to properly mixed lower quality materials.

2. Increased set-up time – Materials in which too much water has been added will not set-up at the rate which they were designed to. In some cases, they may not set-up at all and may remain soft, spongey, or grainy. This may lead to the need to remove and re-cast the materials causing long and expensive delays. Furthermore, the rate at which monolithic refractories cure has an impact on the physical properties achieved. Accelerating and decelerating this reaction can have negative implications.

3. Dry-out – Improper mixing of monolithic refractories can cause significant problems during the refractory dry-out process. More water leaving the lining can lead to excess steam and pressure causing linings to crack, spall, or even explode during the dry-out. Furthermore, since the materials were improperly mixed in the first place, the physical properties associated with the material are likely reduced which compounds the problems potentially experienced during the dry-out period.

There are ways to insure that materials are properly mixed. These methods include adequate training of the workforce, proper communication, have the mixing and use instructions available during an installation, have proper measuring devices available, and the use of mixing logs and even third party inspectors.

For more information on how to avoid improper mixing of refractory materials on your next important project, reach out to Schad today.