The quality decline of low cement refractory castables may be caused by the following reasons:
I. Raw materials
1• Cement quality problems: The calcium aluminate content of cement is unstable, the fineness is unqualified, or it is damp and deteriorated, which will affect the setting time and strength development of the castable, resulting in quality decline.
2• Aggregate and powder problems: The unreasonable particle grading of aggregates will reduce the bulk density of the castable, increase the porosity, and reduce the strength. If the impurity content of aggregates and powders is high, especially if they contain components that affect the refractory performance, the refractoriness and high-temperature performance of the castable will be reduced.
3• Additive problems: Improper selection of additives such as water reducers and coagulants or inaccurate dosage may cause abnormal performance such as fluidity and setting time of the low cement refractory castables.
II. Production process
1• Uneven mixing: If the mixing time is too short, cement, aggregates, powders and additives cannot be fully mixed, which will cause uneven distribution of internal components of the castable, affecting the consistency and stability of its performance.
2• Improper molding pressure: If the molding pressure is too high, the aggregate may be broken, the particle structure may be destroyed, and the strength of the castable may be reduced; if the pressure is too low, the density of the castable is not enough, the porosity will increase, and the strength and anti-erosion performance will be reduced.
3• Poor curing conditions: If the curing temperature is too low or too high, the humidity is insufficient, etc., it will affect the hydration reaction of cement, so that the castable cannot obtain good strength and performance.
III. Construction and use
1• Construction environment problems: If the construction environment temperature is too low or too high, and the humidity is too high, the water of the castable will evaporate too quickly or too slowly, affecting its coagulation and hardening process.
2• Unreasonable baking system: If the baking temperature rises too fast, the water inside low cement refractory castables will evaporate rapidly, resulting in greater internal stress, leading to cracking, peeling and other problems, reducing its service life.
3• Harsh working conditions: During use, if it is in harsh working conditions such as ultra-high temperature, strong erosion, and high scouring for a long time, it will accelerate the damage of the castable and reduce its quality.
