Investigation of the Testing Parameters Influencing the Cold Crushing Strength Testing Results of Refractory Materials

摘要

Compressive strength is commonly used for characterising the properties of refractory materials. There are a number of standards, which specify the methodology applied for testing dense shaped materials, insulating materials and unshaped materials. They contain requirements regarding the shape and size, the dimensional tolerance of test pieces, the manner of their preparation, the load rate and preload applied, the hardness and roughness of loading plates as well as the use of packing. These testing parameters are not fully defined in all the standards. Moreover, there are testing parameters not defined in standards, which can influence the obtained results of cold crushing strength (CCS). The article presents investigations conducted within the framework of ReStaR project, aimed at determining the influence of testing parameters related to the CCS determination procedure on the testing results. In order to identify testing parameters that have the greatest influence on CCS determination in the case of dense formed, insulating and unshaped materials, the factorial design and variance analysis methods were applied. For each of these materials, each of the influencing factors on two adopted levels was examined. It was found that a considerable impact on the determination result was exerted by the quality of preparing the test pieces, their format, in particular the application of preload and load rate in the case of unshaped products. It should be noted that the influence of the last one is different for dense products and insulating ones. The application of packing exerts a strong effect on a decrease of CCS value. In case of dense and insulating materials for factors chosen after preliminary tests, it was found that none of the tested factors is important if the results obtained in four laboratories are treated as one population, whereas for each laboratory the important factors were different. It means that the amount of experiments determines the quality of the test results. In case of unshaped materials, preparation and format of test pieces plays a key role for CCS testing results.