On-site operation and use steps of refractory castables
During use, the amount of water added is particularly important, but on-site control is the most important.
01. Add the bagged castable
During on-site construction, the mixer should be cleaned first, and there should be no sundries. Then pour the bagged pouring material into the forced mixer with no more than 20% of the predetermined capacity of the mixer each time.
At present, ton bags are used for outer packaging, and there are small bags of 25kg or 50kg inside. The aggregate and binder are packed separately. When pouring into the mixer, be sure to pay attention to the binder in the plastic small bag, and it cannot be poured together with dry powder. Pour the dry mix in the 25kg bag first, dry mix it in the mixer for 1-2 minutes, and then add the binder and stir.
02. Add water and stir
The next step is to add water and stir, add water according to the manufacturer’s instructions to add 90% of the water, and stir for 2-3 minutes. The remaining amount of water is added as appropriate. Don’t add more if you don’t need to add more, add as little water as possible. If you need to continue to add water, you can use it after adding water and stirring for 3 minutes. Remember to stir and add clean water from the water pipe, and never use rainwater or mountain spring water.
Whether the amount of water added is appropriate, you can use your hands to knead the mixed mud into pellets, then throw the pellets about 30cm high, and catch the pellets with your hands to deform without stopping, indicating that the amount of water added is just right; if the pellets are deformed and removed from the hand If the pellets flow out from the cracks, it means that the amount of water added is too much; if the pellets crack and fall apart, it means that the amount of water added is too small. Since the amount of water added directly affects the strength, drying and service life of the refractory castable, the amount of water added should be reduced as much as possible under the conditions of construction.
03. Join the mold
When pouring begins, remove debris from the mold. Set and fix the heat insulation layer of the furnace shell filled with expansion joints, build the insulation layer, fill the stirred material into the mold, and vibrate with a vibrating rod. The thickness of the paving should not exceed 1.2 times the length of the vibrating rod; the vibrator should be slowly inserted into the pouring body, vibrate until the surface is flooded and then move the vibrating rod. Vibrate the vibrator at each position for 4 to 5 minutes, if the time is too long, particle segregation will occur.
04. Start pouring
Pouring starts from the bottom of the furnace wall, and goes up layer by layer and block by block. Each layer starts at the corner. During pouring, it is necessary to prevent the formwork from being squeezed, which will affect the construction quality. When pouring the furnace wall, a layer of linoleum paper needs to be laid every time a certain height is poured, and then continue to pour.
When pouring the furnace roof, the thickness must be poured at one time, and layered pouring is not allowed. The value of the expansion joints of the lining and its distribution position and structure, the expansion joints are left according to the expansion rate, generally an expansion joint of 8mm-10mm is left every 2 meters, and the expansion joints must be vertically connected. During construction, fix the filling board in the expansion joint, and leave 1-2 expansion lines between the two expansion joints, with a width of 2mm.
When the furnace top is poured with anchor bricks, it should be constructed until the lower surface of the anchor bricks is about 2cm higher, and then the anchor bricks can be hung to ensure that the bottom of the anchor bricks is closely combined with the castable. To vibrate, you only need to shake it with a vibrator or stir it with a wooden stick.
05. Precautions for construction in winter
During construction in winter, the temperature around the construction should not be lower than 5°C. The added water can be heated to no more than 50°C, and the stirring time should be extended appropriately. After pouring construction, maintenance must be carried out, and measures to keep warm should be taken when the temperature is lower than 5°C. The formwork can only be removed after maintenance. When removing the formwork, all the wooden formwork should be removed, otherwise the wood board will burn during the oven, causing the surface layer to peel off and produce cracks.