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Winter construction and maintenance of cement refractory castables for industrial furnaces

Date:2022-07-13Hits:270

1 cement, formwork and other materials should be transported to the greenhouse for storage before construction.

2 the mixing water should be heated, and the heating temperature should meet the following requirements:

① The water temperature of ordinary portland cement refractory castables of and above shall not exceed 60 ℃;

② The water temperature of aluminate cement refractory castable shall not exceed 30 ℃.

3 cement shall not be heated directly.

4 when the required temperature cannot be reached after heating the water, the aggregate can be heated. The aggregate heating temperature of 42.5 and above ordinary portland cement refractory castables shall not exceed 40 ℃; The aggregate heating temperature of aluminate cement refractory castable shall not exceed 30 ℃.

5 the aggregate can be heated by heating kang, heating or steam in the exhaust pipe, and it is not allowed to be heated directly by flame.

5.2 mixing

5.2 refractory castables shall be batched according to the specified mix proportion, and the measurement shall be accurate. Cement, aggregate and powder shall be measured by weight, while water and admixture solution can be measured by volume.

5.3 mixing should be carried out in the greenhouse, and the ambient temperature should not be lower than 5 ℃.

5.4 the mixing time shall be in accordance with the construction instructions or product instructions. If there is no specific requirement for mixing time, the mixing time should not be less than 3mm, and the total mixing time should not exceed 5mm. Mixing should be carried out according to the following procedures:

① First add coarse and fine aggregates, then add powder and cement, mix evenly, and then add 2/3 of the water volume, and mix for lmin ~ 1.5min;

② Add the remaining 1/3 of water and stir well.

5.5 refractory castables shall be mixed by forced mixer. When changing the material brand, the mixing machine, hopper and weighing container should be cleaned.

5.6 the mixed refractory castable shall be poured within 30mm, or within the specified time according to the product instructions. Refractory castables with initial set shall not be used.

6. Transportation

Thermal insulation measures should be taken for transportation equipment, and the number of loading, unloading and reshipment should be reduced.

The transportation equipment shall Firm and clean.

The transportation equipment shall be cleaned when each team works or changes the product brand.

templates installing

The formwork installation shall be accurate and stable, and the formwork joints shall be tight. Materials used for reserved expansion joints shall be firm.

Before pouring, the size of formwork, the firmness of support, the tightness of joints, the position of reserved holes, etc. shall be checked, and the sundries in the formwork shall be cleaned.

During pouring, the formwork shall be free of deformation, displacement and slurry leakage, and anti sticking measures shall be taken. Connectors and reinforcements shall not be disconnected.

pouring

The temperature of refractory castable before casting should not be lower than 10 ℃. The temperature of the surface in contact with the refractory castable shall not be lower than 5 ℃.

The pouring of refractory castables shall be in accordance with the current The standard "code for construction and acceptance of industrial furnace masonry engineering" gb50211 shall be implemented.

6. Curing and demoulding

1. After the construction of fire-resistant castables, they should be cured in the greenhouse according to the maintenance regulations of normal temperature. During the curing period, the refractory casting body shall not be subjected to external forces, vibration and load, and the curing temperature shall be stable.

2 before the initial setting of refractory castables, the exposed surface should be plastered and pressed twice, and should be covered with plastic film and thermal insulation materials, which should be removed when the formwork is removed.

3 during winter construction of fire-resistant castables prepared with different cements, the curing system shall be selected according to the cement performance in table 6.1.3 for timely curing after initial setting.

Table 6.1.3 curing system for winter construction of refractory castables prepared with different cements

Aluminate CA-50 cement refractory castables should not be directly cured by steam, and the ambient temperature should not exceed 25 ℃;

2. Steam curing system: the time of heating constant temperature cooling should be 4H ~ 10h ~ 4h, the heating rate should be 10 ℃ /h ~ 15 ℃ /h, not more than 20 ℃ /h, and the cooling rate should not exceed 40 ℃ /h.

4. The heating shed method should use heaters such as steam exhaust pipes and electric heaters to heat the air in the shed, and the curing ambient temperature should not be lower than 5 ℃. During the curing period, the relative humidity in the greenhouse shall be monitored and humidification measures shall be taken The surface of the casting body is wet.

5 when the integrally poured fire-resistant casting body is cured by the greenhouse method, the temperature rise and fall speed should meet the following requirements:

1. When the surface coefficient is greater than or equal to 6, the heating rate should not exceed 15 ℃ /h, and the cooling rate should not exceed 10 ℃ /h;

2 when the surface coefficient is less than 6, the heating rate should not exceed 10 ℃ /h, and the cooling rate should not exceed 5 ℃ /h.

6 when using heat storage method for curing, it should be insulated, and the thickness of the insulation layer at the edge and convex corner should be 2 ~ 3 times that of the large surface. Water loss shall be prevented during curing.

6.2 demoulding and maintenance

6.2.1 the non bearing formwork shall be able to When it is not damaged due to formwork removal, the load-bearing formwork can be removed above 70% of the design strength of the refractory casting body.

6.2.2 after the fire-resistant casting body is cured, it should be baked in time.

6.2.3 when the refractory casting cannot be dried in time after curing, corresponding protective measures shall be taken.