What are the precautions for refractory castables in use?

Refractory castables should pay attention to the following four key links during use, namely mixing, pouring, curing, and baking. Problems in any one of these links may lead to product performance degradation or use.

1. Mix

Mixing is divided into mechanical mixing and manual mixing. At present, the industry adopts compulsory or mortar mixer mixing, and does not use manual mixing. Equipment and tools: compulsory or mortar mixers, buckets, scales, vibrators, tool shovels, trolleys, etc.

The construction water consumption is based on the water consumption indicated in the quality inspection sheet of the batch of products, and it is strictly implemented in accordance with the standard to achieve accurate measurement.

Mixing: dry mix first and then wet mix. In the order of first large bags and then small bags, put the bulk materials into the mixer and dry mix for 1-3min to make it mix evenly. The weight of each mix is determined according to the mechanical and construction amount; According to the material weight, accurately weigh the water required for each mixing according to the specified water consumption, add it to the dry material that has been evenly mixed, and stir thoroughly. The time is not less than 3min, so that it has suitable fluidity, and then the material can be discharged for pouring.

Note: (1) The tools used in the construction process such as agitators, buckets, tool spades, etc. need to be cleaned up in advance, and lime, gravel, Portland cement and other impurities should not be mixed. (2) The water used when mixing must be clean tap water. In the case of vibrating pulp, as little water as possible, a better construction effect has been achieved. (3) The amount of mixing each time is not easy to be too much, and it should be determined according to the type and model of the mixer, otherwise it will cause the mixer to be stuck and stalled. The remaining coagulated blocks cannot be mixed again with water.

2. Pouring

Before the construction of the pouring material, it is necessary to check whether the anchor is welded firmly, and heat-resistant nails should be used for parts above 500 °C. The surface of the anchor should be coated with 0.5-1mm thick paint or wrapped with plastic tape to buffer the expansion force after heating, and remove the debris in the mold.

The freshly mixed castable should be poured quickly, generally within 20min. Pour the mixed castable into the mold, and insert the vibrating rod into the vibrating in time, and the vibration should be even. The surface of the castable is turned and discharged with bubbles, and the vibrating rod is moving when the surface is slurry, the moving speed is 1-2m/min, and the speed is slow when pulling out the vibrator.

Before solidification after pouring, the on-site temperature must be kept above 10 °C (10-30 °C), and the on-site temperature is lower than 10 °C, corresponding heating and warmth measures must be taken, otherwise it will cause slow coagulation and lead to a decrease in product performance.

Note: (24) The surface of the vibrated castable should be kept natural, and it is not suitable to use tools to wipe it, and it is not allowed to sprinkle cement fine powder on the surface. (10) The vibrating rod should have a spare to avoid that when the vibrating rod fails, the spare rod can be activated in time. (20) After the completion of construction, within 100h of the construction body, especially before the castable hardening, it is strictly forbidden to move, shake or pound, otherwise, the cast body will produce cracks or even complete destruction. (<>) The castable should be continuously constructed, and when the construction cannot be continuous for various reasons, the construction joint can be left and left at the expansion joint, otherwise the construction joint is made into a hemp surface, that is, a cross groove with a depth of <>mm and a width of about <>mm on the castable, with a spacing of about <>mm.

3. Maintenance

The main tools used are polyethylene plastic film, straw bags, etc. Ambient temperature requirements and control: the curing temperature of the casting body is between 15-35 °C, beyond this temperature range, corresponding heating or cooling measures should be taken, otherwise it will cause the performance of the product to decline.

After the castable hardens, it is necessary to cover the surface of the construction body with polyethylene plastic film immediately, and then cover it with a wet grass bag to prevent water evaporation and promote cement activation. After hardening, it is forbidden to knock and shake within one day, according to the hardening situation, generally after hardening 24-30h can be demolded.

After demolding, it is necessary to cure for two days, and continue to cover with polyethylene plastic film and wet grass bags during maintenance. After three days of curing, remove the plastic film and straw bags. Let the hardened body dry naturally in the air for one day, and it can be baked.

4. Bake

Baking is the last key link in the use of castable, because the castable body is relatively dense, so it is absolutely forbidden to heat up too fast when baking, otherwise it will cause cracking accidents.