After the anchor welding, calcium silicate board laying, and mold support of the cement rotary kiln lining, the construction of the refractory castables should be carried out in the following way.
Inspection: Check the packaging and factory date of the castable, which generally has a shelf life of 6 months, avoid moisture, and conduct a pre-test to check whether it is invalid; check the appearance and cleanliness of the equipment to be cast; check the integrity of the construction machinery and tools, and vibrating tools and other tools must have intact spare parts; check the type, size, layout and welding quality of the anchors, and the metal anchors must be well treated with asphalt paint, plastic caps and other expansion compensation treatments; check the surrounding refractory brick linings and insulation layers to prevent water loss of castables; check the construction water, and its water quality must reach the quality of drinking water; check whether the cast equipment has parts, if loose, it must be fastened with iron plates and then welded.
If the above items are unqualified, they should be treated and qualified before construction. Expired and invalid materials shall not be used. During the construction of refractory castables, it is necessary to ensure that there is no power outage, water outage, or interruption of construction. Especially when pouring the top of the kiln head cover, once the construction is stopped in the middle, the pouring layer will have a sandwich phenomenon, the hot air entering the layer seam will burn the anchors, and the castable will collapse.
The amount of water added to the castable should be strictly controlled according to the instructions for use and must not exceed the limit. Under the premise of ensuring the construction flow performance, the amount of water added should be less rather than more. Pay attention to using clean water to avoid other components or debris in the water affecting the solidification.
The mixing time of the castable should be no less than 5 minutes. It is strictly forbidden to use manual mixing. When mixing, dry mix in advance. After dry mixing is uniform, add 80% of the required water and stir. Then, depending on the dryness and wetness, slowly add the remaining water and continue stirring until a suitable working consistency is obtained. When mixing castables of different qualities, the mixer should be cleaned first.
The refractory castables must be used in whole barrels and bags. The mixed castable is generally used up within 30 minutes. In a high-temperature and dry working environment, this time should be appropriately shortened. The castable that has been initially solidified or even agglomerated must not be poured into the mold frame. It is strictly forbidden to add water and stir for secondary use.
The castables poured into the mold should be immediately vibrated in layers with a vibrating rod. The height of each layer should be ~<300mm, and the vibration interval should be about 250mm. Try to avoid touching the anchors during vibration, and do not vibrate or re-vibrate at the same position for a long time. After seeing the slurry on the surface of the castable, the vibrating rod should be slowly withdrawn to avoid segregation and voids in the castable layer. The cast body after pouring should not be subjected to pressure or vibration before solidification.
When pouring a large area, it should be constructed in blocks. The area of each pouring area should be 1.5~2.0m. Expansion joints should be left every 2.0m with plywood, and no omissions should be made. Expansion joints should be left at the intervals of anchors.
After the surface of refractory castables material is dry, the part exposed to the air should be covered with plastic film immediately. After the initial setting, it should be regularly watered to keep the surface moist. The curing time is at least 2 days. Water should be frequently sprinkled on the first day. After the final setting of the castable material (generally 6-8 hours), the side formwork can be removed and watering can be continued. However, the load-bearing formwork can only be removed after the strength reaches 70% (generally 48 hours).
After the formwork is removed, the cast body should be inspected in time. Quality problems such as honeycombs, peeling and voids should be handled and repaired in time. If the problem is serious, the defective part should be chiseled off to expose the anchor, and then filled with the same quality of castable material and compacted, and continued to be cured. It is forbidden to replace it with cement mortar.
