ASTM C656-17(2023)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C656 − 17 (Reapproved 2023)
Standard Specification for
Structural Insulating Board, Calcium Silicate
This standard is issued under the fixed designation C656; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This specification covers structural insulating board for 2.1 ASTM Standards:
general thermal insulating, fire-resistive, and marine bulkhead C165 Test Method for Measuring Compressive Properties of
applications. The rigid, preformed structural insulating board is Thermal Insulations
for use at temperatures up to 1700°F (927°C). For specific C168 Terminology Relating to Thermal Insulation
applications, the actual temperature limit shall be agreed upon C177 Test Method for Steady-State Heat Flux Measure-
between the manufacturer and the purchaser. ments and Thermal Transmission Properties by Means of
the Guarded-Hot-Plate Apparatus
1.2 The structural insulating board maintains its structural
C203 Test Methods for Breaking Load and Flexural Proper-
integrity after immersion in water.
ties of Block-Type Thermal Insulation
1.3 Rapid cycling over a wide temperature range is not
C303 Test Method for Dimensions and Density of Pre-
recommended because of potential damage due to thermal
formed Block and Board–Type Thermal Insulation
shock.
C356 Test Method for Linear Shrinkage of Preformed High-
Temperature Thermal Insulation Subjected to Soaking
1.4 The values stated in inch-pound units are to be regarded
as standard. The values given in parentheses are mathematical Heat
C390 Practice for Sampling and Acceptance of Thermal
conversions to SI units that are provided for information only
and are not considered standard. Insulation Lots
C411 Test Method for Hot-Surface Performance of High-
1.5 When the installation or use of thermal insulation
Temperature Thermal Insulation
materials, accessories and systems, may pose safety or health
C447 Practice for Estimating the Maximum Use Tempera-
problems, the manufacturer shall provide the user appropriate
ture of Thermal Insulations
current information regarding any known problems associated
C518 Test Method for Steady-State Thermal Transmission
with the recommended use of the company’s products, and
Properties by Means of the Heat Flow Meter Apparatus
shall also recommend protective measures to be employed in
C1045 Practice for Calculating Thermal Transmission Prop-
their safe utilization. The user shall establish appropriate safety
erties Under Steady-State Conditions
and health practices and determine the applicability of regula-
C1058 Practice for Selecting Temperatures for Evaluating
tory requirements prior to use.
and Reporting Thermal Properties of Thermal Insulation
1.6 This standard does not purport to address all of the
D1037 Test Methods for Evaluating Properties of Wood-
safety concerns, if any, associated with its use. It is the
Base Fiber and Particle Panel Materials
responsibility of the user of this standard to establish appro-
E136 Test Method for Assessing Combustibility of Materials
priate safety, health, and environmental practices and deter-
Using a Vertical Tube Furnace at 750 °C
mine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accor-
3. Terminology
dance with internationally recognized principles on standard-
3.1 Definitions—The definitions in Terminology C168 shall
ization established in the Decision on Principles for the
apply to the terms used in this specification.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
4. Classification
Barriers to Trade (TBT) Committee.
4.1 The structural insulating boards shall be of the following
types:
This specification is under the jurisdiction of ASTM Committee C16 on
Thermal Insulation and is the direct responsibility of Subcommittee C16.20 on
Homogeneous Inorganic Thermal Insulations. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved March 1, 2023. Published March 2023. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1970. Last previous edition approved in 2017 as C656 – 17. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/C0656-17R23. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C656 − 17 (2023)
4.1.1 Type I—Maximum use temperature 1400°F (760°C).
Length Width Thickness
1 1 1
± ⁄8 in. (3 mm) ± ⁄8 in. (3 mm) ± ⁄16 in. (1.5 mm)
4.1.2 Type II—Maximum use temperature 1700°F (927°C).
9. Workmanship, Finish, and Appearance
4.2 The structural insulating boards shall be of the following
grades:
9.1 Calcium silicate structural insulating boards shall not
3 3
4.2.1 Grade 1—Typical density 36 lb/ft (577 kg/m ).
have visible defects, such as major cracks, lumps, or excessive
3 3
4.2.2 Grade 2—Typical density 46 lb/ft (737 kg/m ).
departure from planeness, which adversely affect service quali-
3 3
4.2.3 Grade 3—Typical density 60 lb/ft (961 kg/m ).
ties.
3 3
4.2.4 Grade 4—Typical density 14 lb/ft (224 kg/m ).
3 3
10. Qualification Requirements
4.2.5 Grade 5—Typical density 18 lb/ft (288 kg/m ).
3 3
4.2.6 Grade 6—Typical density 28 lb/ft (449 kg/m ).
10.1 Unless otherwise specified, the following requirements
3 3
4.2.7 Grade 7—Typical density 40 lb/ft (641 kg/m ).
shall be employed for the purpose of initial material or product
3 3
4.2.8 Grade 8—Typical density 60 lb/ft (961 kg/m ).
qualification.
10.1.1 Compressive strength,
5. Ordering Information
10.1.2 Screw holding strength,
5.1 The type, grade, and dimensions shall be specified by
10.1.3 Linear shrinkage and temperate of use,
the purchaser.
10.1.4 Apparent thermal conductivity, and
10.1.5 Combustion characteristics.
5.2 When a certification or test report, or both, are required,
it shall be specified by the purchaser.
11. Sampling
11.1 Calcium silicate structural insulating boards shall be
6. Materials and Manufacture
sampled in accordance with Practice C390. Specific provisions
6.1 Calcium silicate structural insulating board shall be
for sampling shall be agreed upon between the purchaser and
composed of hydrated calcium silicate with natural or man-
the supplier.
made fibers or fillers, or a combination thereof. Asbestos shall
not be used as an ingredient or component of the product.
12. Test Methods
12.1 Dimensions and Density—Use Test Method C303,
7. Other Requirements
except that specimens shall be full-size sheets for determina-
7.1 Calcium silicat
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