Construction requirements of acid-resistant refractory castables
1、The construction of acid-resistant castables should ensure that the power is not stopped and the construction is not interrupted.
2、The template for the construction of acid-resistant castables can be made of steel plate or hardwood board. The template should have enough strength, good rigidity, no deformation, no displacement and no leakage. Steel template should be coated with release agent and wooden template should be painted with waterproof paint. The reused template should be cleaned and painted first before use.
3、The amount of water added to the casting material should be controlled strictly according to the instruction, and should not exceed the limit. Under the premise of guaranteeing the construction performance, it is better to add less water than more.
4、The mixing time of casting material should be not less than 5 minutes. Use the forced mixer when operating. When mixing, it is advisable to dry mix beforehand, then add 80% of water to mix, then depending on its dryness and wetness, slowly add the remaining water to continue mixing, until the suitable working consistency is obtained. When mixing different castables, the mixer should be cleaned first.
5、Castables must be used in whole barrel and whole bag. The mixed castables are usually used up within 30 minutes. In the high temperature and dry working environment, this time should be shortened appropriately. The castables which have already set or even caked shall not be poured into the mould frame, nor shall they be stirred with water.
6、The acid-resistant castable material poured into the mould frame should be immediately shaken by vibrating rod in layers, the height of each layer should be no more than 300mm, and the vibration distance should be about 250mm. Try to avoid touching the anchorages when vibrating, and not to vibrate and re-vibration in the same position for a long time. The vibrating rod should be withdrawn slowly after the surface of the pouring material is seen to return to the slurry, so as to avoid segregation and hollowing of the pouring material layer.
After the casting is finished, the casting body cannot be pressurized and shocked again before solidification.
7、When pouring large area, it should be constructed in blocks. The area of each casting area should be about 1.5m2. Expansion joints should be left according to the design and should not be omitted. Expansion joints should be left in the position of the anchor interval.
8、After the surface of acid-resistant castable is dried, the part exposed in the air should be covered tightly with plastic film or straw bag immediately. After the initial condensation arrives, it should be sprinkled with water regularly to keep its surface moist. The maintenance time is at least two days, and the water should be sprinkled diligently during the first day. After the final condensation of the casting material, the side mold can be removed to continue the sprinkling maintenance, but the load-bearing template must wait until the strength reaches 70% before demoulding.
9、After the removal of the formwork, the casting body should be inspected in time. The quality problems such as honeycomb, spalling and cavity should be dealt with and repaired in time. When the problem is serious, the defective part should be chiseled away to reveal the anchorage, and then filled with the same quality of pounding material and pounding, and continue maintenance.
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