Stability refers to the property of a plastic material that exhibits elastic behavior and does not immediately fail after yielding under special structural loading conditions. For example、 a structure that causes discontinuous stress or thermal stress、 after a few loading and unloading cycles in the initial stage、 will undergo certain plastic deformation、 and no new plastic deformation will occur in subsequent loading and unloading cycles、 that is、 plastic fatigue or ratcheting phenomenon will not occur、 At this point、 the structure is in a stable state. When using the test cake method for inspection、 it is required that the production of the test cake must be standardized. If the diameter is too large or too small、 and the edges are blunt、 it will affect the test results. Generally、 the standard test cake is a cake with a diameter of 70-80mm、 a center thickness of about 10mm、 gradually thinning edges、 and a smooth surface. After cooking、 the stability test cake should be checked with a ruler to ensure it is not bent. If there is only a small amount of peeling under the premise of no cracks observed with the naked eye、 it should be judged as qualified for stability. Before boiling the test cake、 it should be checked and recorded for any cracks or bending. To check whether the curing temperature and humidity of the test cake meet the requirements (the humidity curing box should be able to control the temperature at 20 ± 3 ℃、 humidity greater than 90%、 and curing time of 24 ± 2 hours). If the curing temperature is too high (greater than 25 ℃) or the humidity is insufficient、 it may cause shrinkage cracks in the test cake before boiling、 especially when the specific surface area of cement is relatively large、 which is more prone to shrinkage cracks (shrinkage cracks often occur in the middle of the bottom of the test cake in contact with glass). At this time、 it cannot be considered that the sample is unstable; If the curing temperature is too low (less than 15 ℃)、 peeling may occur after boiling. When using the Rayleigh clamp method for inspection、 the increase in distance between the tips of the two pointers of the boiled Rayleigh clamp test mold is measured to determine whether the stability is qualified. If the increase is not more than 5.0 millimeters、 it is considered that the cement volume stability is qualified. When there is a dispute between using the cake test method and the Leigh clamp method to determine the same cement sample、 the Leigh clamp method shall prevail P>
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