API TR 983 PDF
This technical report documents an observed anomaly with the permanent linear change (PLC) of insulating castables with a density less than 1280 kg/m3 (80 pcf). The curing time is shown to impact the permanent linear change when samples are subsequently fired to 816 °C (1500 °F). The sample preparation and testing were performed by an independent laboratory on behalf of the API Refractory Projects Group.
Disclaimer: This report only reviews the data from one castable material, which was only tested by one laboratory. Therefore, it may not be conclusive that this anomaly is applicable to all castables with a density less than 80 pcf. While originally adapted from fired refractory brick testing, it should be noted that PLC has been a longstanding physical property measurement for castables to monitor and control the permanent linear shrinkage. Over this extended period of commercial practice, the test has proven to be an effective tool to monitor excessive shrinkage cracking during initial heating of newly installed castable linings without time-factoring for the anomaly before firing. Further study is required to determine if this anomaly is unique to the refractory formulation or more widely relevant to the overall population of lightweight, castable refractories being manufactured from a wide range of raw materials and additives to make products that otherwise appear similar.
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