What is the ratio of aggregate, powder, and binder in amorphous refractory castables?
We all know that amorphous refractory castables consist of aggregates, powders, and binders. How should we mix so many materials? Below is a detailed breakdown by Chongde Refractory, hoping to be helpful to you.
1、 What principles should be followed for the proportioning of castable aggregates, powders, and adhesives?
The principle of preparing refractory castable is to reasonably select particle size distribution, ultrafine powder, and the variety and dosage of additives.
The large quantity and particle size of refractory aggregate are determined by the thickness of the engineering lining, usually 10mm or 5mm, and its particle grading is; 40% to 50% for sizes ranging from 10 to 5mm, 20% to 30% for sizes ranging from 5 to 3mm, and 20% to 30% for sizes ranging from 3 to 0.1mm; Alternatively, 40% to 60% for 5-3mm, 20% to 30% for 3-1mm, and 15% to 25% for 1-0.15mm. Generally speaking, a third or fourth grade grading is used to achieve the maximum bulk density. The amount of refractory aggregate used is 68% to 72%.
The dosage of refractory powder is 18% to 25%, including 5% to 10% for high-end materials, 2% to 12% for refractory ultrafine powder, and a total of 28% to 32% for refractory powder and ultrafine material.
2、 What are the characteristics of refractory castables compared to fired bricks? Refractory castables are essentially refractory concrete. Compared to fired refractory bricks, refractory castables have the following characteristics in terms of performance:
(1) The softening temperature under load is much lower than that of homogeneous refractory bricks.
(2) The linear expansion coefficient is relatively small, and due to the sintering shrinkage effect of the binder during the heating process, it can offset the expansion of a portion of the aggregate during heating.
(3) Good resistance to sudden temperature changes, with a cold and hot exchange frequency of over 15 times, better than homogeneous refractory bricks.
(4) The shrinkage of the re fired line is generally larger than that of refractory bricks.
(5) The overall performance is better than that of fire-resistant masonry.
3、 How many methods are there for building refractory castable furnaces? What are the several situations of on-site pouring?
There are two common construction methods for refractory castables; One is to directly pour and compact on site, and the other is to prefabricate and form. There are three situations of direct pouring and compacting on site: overall pouring and compacting (such as small chamber furnaces); Partial pouring and compaction forming (such as heating furnace roof) and partial pouring and compaction forming or repairing (such as leveling walls and arches that are difficult to lay bricks).
4、 How to determine the plasticity index during on-site construction? Answer: A small fire-resistant plastic with a suitable plasticity index can be kneaded into a ball by hand, without water secretion, touching or loosening.
How many types of ramming materials are there? How to compact the construction? Answer: There are two types of ramming materials: hot ramming and cold ramming.
During construction, first remove dirt or rust, apply adhesive, and then lay the material layer by layer (100mm thick), and compact it layer by layer. Use pneumatic keys in zones (strips or sections), and use one hammer to press half or one-third of the hammer to vibrate back and forth in a straight shape for 2-3 times. When using hot tamping, the hammer head should be heated to a dark red color (divided into large, medium, and small hammers), and the wind pressure should not be less than 0.5MPa. The upper and lower layers should be staggered at a certain angle, and the compaction should be carried out continuously in one go to prevent separation