How to Maintain Several Common Refractory Castables
Several commonly used refractory castables - silicate cement refractory castables, aluminate refractory castables, water glass refractory castables, and phosphoric acid (or phosphate) refractory castables. What are the precautions to be taken when maintaining them?
Due to different types of refractory castables, their curing time and environmental requirements also vary.
1、 Maintenance precautions for silicate based refractory castables:
1. Silicate refractory castables are suitable for watering and curing, allowing the cement in the product to form dehydration and hardening during the hydration process. The maintenance of high alumina cement castables is particularly important because the cement hydration and reinforcement in high alumina cement castables products are fast. And generate a large amount of exothermic reactions, which can easily cause cracks on its surface.
2. Wet curing should be covered and watered after the hardening of the pouring material begins. The watering frequency should be sufficient to maintain the pouring material in a damp state.
3. The heating rate for steam curing of Portland cement refractory castables should be 10-15 ℃/h, and the maximum should not exceed 20 ℃/h; The cooling rate should not exceed 40 ℃/h.
2、 Precautions for maintenance of water glass pouring material:
The strength increase of water glass castable is generated during the dehydration process of silica gel. So it should be maintained in a dry environment for maintenance, rather than watering for maintenance.
3、 The maintenance precautions for phosphate refractory castables include:
1. Phosphoric acid refractory castables should not be cured with water or steam, but should be cured in a dry environment.
2. If the ambient temperature is low, low-temperature drying is required after pouring.
1.1 Preparation of raw materials
The finished refractory casting material should undergo necessary technical inspection before construction, and can only be put into use after confirming that it meets the design requirements.
The refractory casting materials provided by the construction site should be selected according to the technical requirements proposed in the design. The selected aggregates and powders should be rechecked based on their physical and chemical properties and particle grading. The selected binder should undergo performance testing according to its technical requirements.
1.2 Determination of Mix Proportion
Finished refractory casting materials are usually constructed according to the mix ratio and requirements specified in the construction instructions provided by the manufacturer.
The refractory casting materials provided by the construction site should be sampled and tested through a laboratory. Under the condition of meeting the construction requirements, test blocks shall be made and inspected according to the specified items. The final construction mix proportion can only be determined after the inspection results meet the design requirements.
1.3 Template Preparation
The template used for the construction of refractory castables should be selected based on the characteristics of the engineering structure and the size of the project. The types of templates include fixed, hanging, and tool type. The template materials are usually steel and wood.
When setting up the formwork, the following requirements should be met:
(1) The dimensions are accurate and comply with design regulations.
(2) The support is firm, the template combination installation is convenient for construction, the lap joints are tight, and there is no leakage of grout.
(3) For refractory castables with strong corrosion or adhesion, an isolation layer should be installed inside the template.
(4) Wooden battens reserved for expansion joints shall be firmly fixed to avoid displacement when being vibrated.
(5) Before construction, the formwork should be coated with protective oil to prevent adhesion.
1.4 Anchorage