Dry-out Schedules
why dry-out matters, Sharadaa's role in providing schedules
Products
Industries - Applications
Heat Curing & Dry-out Schedules for Castable Refractories
A controlled dry-out is not optional — it is the most critical step in commissioning a refractory lining. Improper heating causes explosive spalling, structural failure, and premature lining damage. Sharadaa provides product-specific dry-out schedules with every castable supply, ensuring safe and optimal performance from first heat.
Why Dry-out is Critical
What happens if you skip or rush it
Freshly cast refractory linings contain two types of water — free water trapped during installation, and chemically combined water within the binder system. Both must be removed gradually and at controlled temperatures. Applying heat too rapidly converts this water to steam faster than the lining can release it, building internal pressure that exceeds the tensile strength of the refractory — causing explosive spalling, cracking, or complete lining failure.
⚠ Explosive Spalling
Rapid heating traps steam inside the lining. Steam pressure exceeds the refractory's tensile strength — sections blow off the furnace wall violently.
⚠ Structural Cracking
Uneven temperature gradients during heating cause differential thermal expansion, leading to cracks that compromise lining integrity and campaign life.
⚠ Explosive Spalling
Skipping intermediate holds prevents the binder from developing full ceramic bond — the lining never reaches its design cold and hot strength.
⚠ Reduced Campaign Life
Damage sustained during a rushed dry-out is permanent. Even if the lining survives commissioning, its service life will be significantly shortened.
Typical Dry-out Schedule — Four Phases
Applicable to Low Cement and Ultra Low Cement Castables — stricter than conventional grades
Air Curing
Ambient Temperature · 24–48 Hours
After casting, the lining must air cure for a minimum of 24–48 hours. Keep the surface moist using water spray or cover with plastic sheeting to prevent premature surface drying and cracking. Do not apply heat during this phase. The hydraulic bond must develop fully before any thermal load is applied.
Initial Heating — Free Water Removal
Ambient → 110°C · Rate: 10–20°C/hr · Hold: 6–12 Hours
Slowly raise temperature to 110°C to evaporate free water from the castable matrix. A hold at 110°C is mandatory — free water must be fully driven out before further heating. Any steam observed venting from the lining during this phase is normal and expected. Do not advance until steam emission subsides.
Intermediate Heating — Chemically Bound Water Removal
110°C → 350°C · Rate: 15–25°C/hr · Hold: 4–8 Hours · ⚠ Most Critical Phase
This is the most critical and dangerous phase. Chemically combined water (from calcium aluminate hydrates) is released between 200°C and 350°C. The heating rate must be strictly controlled — too fast and steam pressure will exceed the lining's permeability capacity, causing explosive spalling. Extended holds at 250°C and 350°C are recommended for thick linings and LCC/ULCC grades. Never rush this phase.
Final Heating — Ceramic Bond Development
350°C → Operating Temperature · Rate: 25–50°C/hr · Hold at 600°C & 900°C
Once chemically bound water is fully removed, the lining can be heated to operating temperature. Intermediate holds at 600°C and 900°C allow for sintering and ceramic bond formation. The lining develops its design hot strength during this phase. Rate can be increased progressively as the lining becomes more permeable and structurally stable with each hold.
Indicative Heating Rate Reference
Actual schedules vary by product grade, lining thickness, and application — Sharadaa provides specific charts with every supply
Ambient → 110°C
Hold: 6–12 hrs
110°C → 250°C
Hold: 4–6 hrs ⚠
250°C → 350°C
15–25°C/hr
350°C → 600°C
25–35°C/hr
600°C → 900°C
Hold: 2–4 hrs
900°C → Operating
Normal operation
⚠ Critical phase — do not exceed stated rate. Orange/red bars indicate phases most prone to spalling risk.
Sharadaa provides product-specific dry-out schedules with every castable supply.
Our technical team supports dry-out planning, on-site monitoring, and troubleshooting across all industries and installation types. Contact us for application-specific guidance.