What Temperature Can Calcium Silicate Insulation Withstand?

Q: What Temperature Can Calcium Silicate Insulation Withstand?

Standard calcium silicate insulation withstands 650 degree C continuous service temperature (ASTM C533 Type I). High-temperature xonotlite grades withstand 1000-1100 degree C. The difference comes from crystal structure: tobermorite (5CaO.6SiO2.5H2O) degrades above 650 C, while xonotlite (6CaO.6SiO2.H2O) is stable to approximately 1050 C, transforming to wollastonite at 750-800 C without dimensional change. Mingfa produces all three grades: 650 C, 1000 C, and 1100 C.

Calcium silicate insulation is available in multiple temperature grades. Standard grade withstands 650°C continuous service. High-temperature grades withstand 1000°C to 1100°C. The maximum service temperature depends on the calcium silicate hydrate crystal phase formed during autoclave curing.

Temperature Grades at a Glance

Grade	Max Service Temp	ASTM Equivalent	Crystal Phase
Standard	650°C	Type I (649°C)	Tobermorite
High-Temperature	1000°C	Exceeds Type II (927°C)	Xonotlite
Ultra-High-Temperature	1100°C	Exceeds Type II (927°C)	Xonotlite + mineral additives

The Crystal Structure Difference: Tobermorite vs Xonotlite

The temperature rating is determined by the calcium silicate hydrate crystal phase:

Tobermorite (5CaO·6SiO&sub2;·5H&sub2;O) forms at lower autoclave temperatures and pressures. It contains more chemically bound water (approximately 11% by weight). Above 650°C, this water is released, causing crystal structure collapse and significant dimensional shrinkage of 2% or more. Tobermorite-based boards are limited to 650°C service.

Xonotlite (6CaO·6SiO&sub2;·H&sub2;O) forms at higher autoclave temperatures (190-220°C) and pressures (12-18 bar). It contains less chemically bound water (approximately 2.1%), making it thermally stable to much higher temperatures. At 750-800°C, xonotlite undergoes a topotactic transformation to wollastonite (CaSiO&sub3;) with near-zero dimensional change. This gives xonotlite-based boards their reliable performance at 1000-1100°C.

Selecting the Right Grade

Choose based on your continuous hot-face temperature, not peak or process temperature. For cement kilns operating with shell temperatures of 300-400°C, standard 650°C grade is sufficient. For aluminum reduction cells where backup insulation sees 800-950°C, use the 1000°C or 1100°C grade. See our high-temperature insulation panel product page for detailed specifications.

All Mingfa products use xonotlite as the primary crystal phase. Even our standard 650°C grade is xonotlite-based, with the 650°C rating providing a conservative safety margin rather than reflecting a crystal phase limitation.