In unshaped refractories, castables are the "all-purpose" option. Even when they share the same name, performance gaps usually come from two things: bonding system and particle grading. Get the type clear first and you avoid most big mistakes.

[Image: castable packaging + mixing + casting site collage]

01 What is a castable

Refractory castables are made of refractory aggregates, fines, binders, and additives. After adding water or liquid and mixing, they are poured into a mold and vibrated to shape, then fired to form a monolithic lining.

Suitable for: furnace walls, roofs, combustion chambers, flues, repair layers, precast blocks, etc.

02 Three common types

1) Conventional (high-cement) castable

• Features: high construction tolerance, early strength develops quickly
• Drawbacks: average high-temperature performance and slag/thermal-shock resistance; higher post-firing porosity
• Use: areas with moderate temperatures, short maintenance cycles, or tight budgets

2) Low-cement castable (LCC)

• Features: lower cement content, easier to achieve high density, more stable high-temperature strength
• Construction focus: more sensitive to mixing, water addition, and vibration process
• Use: working layers/hot zones with higher strength and corrosion resistance requirements

3) No-cement castable (NCC)

• Features: uses ultrafine powders and chemical bonding instead of cement, suitable for higher temperatures and harsher corrosion
• Challenges: more sensitive to construction and dry-out; parameter drift causes issues
• Use: high-temperature, strongly corrosive areas, or places needing cleanliness and high-temperature stability

03 Three points that most often go out of control on site

• Water addition: a little more makes it easier, but life drops directly; stay within the specified range
• Mixing time: too short causes "false thickening" - looks workable but strength does not develop
• Dry-out schedule: rush the schedule and the lining's internal steam paths fail first

Xinhui typically writes "water window, mixing time, vibration requirements, dry-out milestones" on the batch card. Executing by the card is more stable than relying on experience.

[Image: typical locations diagram: furnace wall/roof/flue/precast block]