Calcium Silicate Insulation Resisting Thermal Cracking

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Solution Overview

Problem

Calcium silicate insulation used in extreme temperature environments, such as the aluminum foundry industry, tends to crack or fail due to temperature fluctuations, necessitating frequent replacement, and there is a need for a more durable solution to extend part life and reduce replacement frequency.

Innovation Solution

A calcium silicate hydrate matrix comprising 51-90 weight percent xonotlite and 10-49 weight percent tobermorite, with added wollastonite and carbon reinforcing fibers, formed into a rigid body with specific proportions to achieve high flexural and compressive strengths, and controlled curing under steam pressure to minimize shrinkage and enhance durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If calcium silicate insulation is used in extreme temperature environments, then good insulating properties and fire resistance are achieved, but cracking and failure occur due to temperature fluctuations

Engineering Contradiction:
Improveextreme temperature resistanceVSAvoiddurability under temperature fluctuations
Core Design Contradiction:
TemperatureVSReliability

Solution Approach 1:

The patent creates a composite calcium silicate material combining multiple phases (tobermorite, xonotlite, and calcium silicate hydrate gel) with controlled pore structures. This composite structure integrates the thermal stability of crystalline phases with the flexibility of gel phases, allowing the material to withstand extreme temperatures while accommodating thermal expansion and contraction, thereby preventing cracking and improving durability under temperature fluctuations.

Inventive Principle:
Principle #40Composite materials

2Duration of action of stationary object

If calcium silicate insulation durability is improved, then part life is extended and replacement frequency is decreased, but material composition and processing complexity increase

Engineering Contradiction:
Improvepart lifeVSAvoidmaterial composition complexity
Core Design Contradiction:
Duration of action of stationary objectVSDevice complexity

Solution Approach 1:

The patent optimizes specific compositional parameters including the ratio of tobermorite to xonotlite crystalline phases, the amount of calcium silicate hydrate gel (5-20%), and pore size distribution (50-200 micrometers). By precisely controlling these parameters during steam curing at 15-20 bar for 6-12 hours, the material achieves enhanced durability and extended part life while maintaining manufacturability through defined processing windows.

Inventive Principle:
Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The resulting insulation material exhibits improved mechanical strength, reduced shrinkage, and increased durability, with flexural strengths of at least 1300 lb/in2 and compressive strengths of at least 2600 lb/in2, while maintaining a low density of less than 55 lb/ft3, effectively resisting cracking and splintering in harsh conditions.

Implementation Method 1

a calcium silicate hydrate matrix having 51-90 weight percent xonotlite and 10-49 weight percent tobermorite

Methodology Applied
Scientific EffectCrystallization: Crystallisation

Implementation Method 2

curing the resulting pressed shape under steam pressure only until the resulting composition includes, in addition to the wollastonite and any residual lime and silica, a calcium silicate hydrate matrix having 51-90 weight percent xonotlite and 10-49 weight percent tobermorite

Methodology Applied
Scientific EffectPhase transformation: Phase Change

Data Source

PatentUS10494304B2High temperature calcium silicate insulation
Publication Date: 2019.12.03 JOHNS MANVILLE CORP

AI summary

A calcium silicate insulation product includes a calcium silicate hydrate matrix that is predominantly but not substantially all xonotlite, for example 51-90 weight percent xonotlite and 10-49 weight percent tobermorite. The insulation product also contains wollastonite, and may include fines of lime and silica and reinforcing carbon fibers. A method of producing the insulation product includes providing the components of the insulation as dry solids, blending the dry solids with water to form a slurry, filter pressing the slurry to form a pressed shape, and curing the pressed shape under steam pressure only until the desired proportions of xonotlite and tobermorite are achieved in the calcium silicate hydrate matrix.