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.
1) Inspection: Check the packaging and factory date of the castables. The general shelf life is 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. Vibrating tools and other tools must have intact spare parts; check the type, size, layout and welding quality of the anchors. Metal anchors must be treated with asphalt paint, plastic caps and other expansion compensation treatments; check the surrounding refractory brick linings and insulation layers to prevent castable water loss; check the construction water. The water quality must reach the quality of drinking water; check whether the cast equipment has loose parts (such as kiln mouth guard iron). If loose, it must be tightened 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 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 casting layer will appear interlayer phenomenon, the hot air entering the layer seam will burn the anchor, and the castable will collapse.
2) The amount of water added to the castable should be strictly controlled according to the instructions for use and shall not exceed the limit. Under the premise of ensuring the construction flow performance, the amount of water added should be less rather than more. Note that clean water should be used to avoid other components or debris in the water affecting the solidification.
3) The mixing time of the castable should be no less than 5 minutes. Manual mixing is strictly prohibited. When mixing, dry mix in advance, and then add 80% of the required water after dry mixing. Then, depending on the dryness and wetness, slowly add the remaining water and continue to stir until a suitable working consistency is obtained. When mixing castables of different qualities, the mixer should be cleaned first.
4) Castables must be used in whole buckets and bags. The stirred castables are generally used up within 30 minutes. In a high temperature and dry working environment, this time should be appropriately shortened. Castables that have 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.
5) 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. After the casting is completed, the cast body cannot be compressed or vibrated before solidification.
6) When pouring a large area, it should be constructed in blocks. The area of each casting 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.
7) After the surface of the castable material is dry, the part exposed to the air should be immediately covered with plastic film. 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).
8) 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 castables of the same quality and compacted, and continued to be cured. It is forbidden to replace it with cement mortar.
In order to pursue construction speed, some construction teams arbitrarily increase the amount of water added to the refractory castables. The mixed castables can be transported to the mold like running water with a rubber hose several meters or even more than ten meters long; the mold strength is poor, resulting in deformation of the lining, or increasing the amount of water added to the castables, affecting the construction quality; the mold is not supported, and the castables are applied manually. This situation is generally used in the construction of the feed pipe lining, and sometimes even in the construction of some preheater cone linings. Expansion joints, gate valves and other equipment should be prefabricated on the ground before installation. These prefabricated parts have strict mold making requirements due to their complex geometric dimensions. The mold is made of metal steel plates and cannot be deformed during construction. Therefore, the mold support must be firm and the mold support position must be correct.