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The improvement of the performance of low-cement castables is actually the application of micro-powder technology, adding water, reasonable construction and proper baking.
There is a certain gap between the stability of low cement castables in actual use and the performance of laboratory castables. The problems that are easy to occur in low-cement castables are: 1. Poor construction performance and poor fluidity; 2. Hardening speed changes greatly, rapid setting and non-setting; 3. Explosive cracking during baking; 4. Shedding phenomenon occurs; 5. Low strength and poor wear resistance. These are all quality problems that lead to abnormal damage of refractory castable products.
In addition to wear-resistant and refractory aggregates, low-cement refractory castables are made of fine raw materials and ultrafine powders, cement and admixtures. By adjusting the proportion of each component, the high-temperature performance of the castables is improved to improve the refractory castables Strength of.
The key construction of low-cement castables should pay attention to: ① Do not increase the water addition of refractory castables arbitrarily, ② The mold support is too high, resulting in excessive water addition of the castables and insufficient compaction; ③ Construction in the lining of the discharge pipe When the mold is not supported, the castable is applied by hand; ④ In order to save the mold, the mold is removed for less than 48 hours, and the mold is removed, resulting in cracking or internal damage of the casting; ⑤ Material, shape, size, welding quality, quantity, anti-expansion treatment, expansion of the anchor The placement of the seam is unreasonable; ⑥ The dry and wet materials are not directly mixed and stirred in accordance with the operation sequence of dry stirring, wet stirring, and unloading, resulting in the inadequate mixing of the casting material, and some materials are not wetted by moisture, making the casting material There is no intensity.
There is also a key water problem. It is necessary to use tap water to avoid the introduction of acid and alkali impurities. It should be added slowly in order to make the dispersant in the powder fully play its role. Excessively high water addition will directly lead to a substantial decrease in the strength of the refractory castable construction body, and the amount of water addition during on-site construction often exceeds the degree of self-flow. The casting body itself is prone to baking cracks when the ambient temperature rises rapidly, resulting in large-scale damage. Once the temperature of the castable itself is lower than 5 ℃, even after curing for 24 h, the castable still has no strength. Construction maintenance must strictly follow the 48-hour mold-removal mechanism. Dry areas must be water-wet, and cold areas must be sealed and heated within 48 hours to ensure the maintenance temperature.
In short, if the above points can be achieved gradually according to the requirements, it will definitely improve the various properties of low cement castables.