Ultra-low cement castables, as the name implies, are refractory castables with low cement addition. The general water addition in the laboratory is 2.5%, and the water addition in on-site construction does not exceed 4%.
Ultra-low cement castables are high-grade refractory castables, which are basically used in key parts of the furnace lining. Because the amount of cement added is small and the calcium content is low, the later use cycle is long; the initial setting time after the on-site construction is completed is more than 10 hours. If the initial setting time is too long, it proves that the amount of water added during on-site construction is too large. Excessive water addition will cause a long initial setting time and affect the construction time of other materials. Therefore, the reason why ultra-low cement castables control the amount of cement added is to control the amount of water added during construction.
Ultra-low cement castables generally use ultra-fine powder technology. In laboratory tests, the general water addition is 2.5%-3%. The proportion in the laboratory is generally lower than the on-site use ratio. It is normal for the water addition to be 1-2% higher during on-site construction, but if it is too large, it will be affected.
However, if the amount of water added during on-site construction increases, a reasonable proportion of water reducer can be added in winter to reduce the amount of water added. Low-temperature baking can be used to allow initial setting. If the weather temperature is suitable, you can wait for initial setting, and then people can stand on the castable. If it can bear the weight of people and the surface of the castable is still hard, you can go down to carry out other castables or other materials.
In short, the amount of water added to ultra-low cement castables is very important. Excessive water addition affects initial setting and continuous construction. Therefore, the amount of water added must be mastered during on-site construction of ultra-low cement materials. Don't be greedy for saving effort and good construction. Excessive water addition will also cause unnecessary effects.
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