GB/T 22459.5-2022 specifies the test method for particle size distribution (sieve analysis) of refractory mortars, applicable to the determination of particle grading for various types of refractory mortars. Based on the type and characteristics of the mortar, the standard provides two test methods: dry sieving and wet sieving. It clearly defines the requirements for sampling, sample preparation, and result calculation. The core equipment includes standard sieves, sieve shakers, balances, and drying ovens. The method involves separating particles of different sizes through sieving, weighing the mass of samples retained on each sieve layer and the pan, and calculating the corresponding mass fractions to characterize the particle size distribution. This provides a unified technical basis for optimizing the construction performance of mortars and ensuring product quality.