ASTM C903 - 15 (2020)

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Designation: C903 −15 (Reapproved 2020)

Standard Practice for

Preparing Refractory Specimens by Cold Gunning

This standard is issued under the ﬁxed designation C903; 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

1.1 This practice covers a procedure for preparing refractory

specimens usually containing calcium aluminate cement with

or without metal ﬁbers by cold nozzle-mix gunning. Specimens

prepared in accordance with this practice are intended for use

in standard ASTM test methods required for evaluating gunned

materials.

1.2 The values stated in inch-pound units are to be regarded

as standard. The values given in parentheses are mathematical

conversions to SI units that are provided for information only

and are not considered standard.

1.3 This standard does not purport to address all of the

safety concerns, if any, associated with its use. It is the

responsibility of the user of this standard to establish appro-

priate safety, health, and environmental practices and deter-

mine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accor-

dance with internationally recognized principles on standard-

ization established in the Decision on Principles for the

Development of International Standards, Guides and Recom-

mendations issued by the World Trade Organization Technical

Barriers to Trade (TBT) Committee.

2. Referenced Documents

2.1 ASTM Standards:

C401 Classiﬁcation of Alumina and Alumina-Silicate

Castable Refractories

C865 Practice for Firing Refractory Concrete Specimens

3. Signiﬁcance and Use

3.1 The properties of refractories can be affected by their

method of installation. This practice attempts to minimize the

variables encountered during installation by pneumatic gun-

ning.

3.2 This practice provides parameters to produce gunned

specimens for use in other ASTM test methods.

3.3 This practice may be used to produce specimens for

acceptance testing, service evaluation, manufacturing control,

and research and development.

3.4 Differences between various kinds of equipment and the

differences in procedures and operator techniques may result in

signiﬁcant variations in the physical properties of the gunned

specimens. It is recommended that the same operator use the

same equipment to produce specimens for referee testing

agreed to by the involved testing parties. The speciﬁc operating

parameters should be shown in the report.

3.5 Although this practice is speciﬁcally designed for re-

fractories containing calcium aluminate cement, it may be used

with minor modiﬁcations for gun mixes containing other bond

systems.

4. Apparatus

4.1 Gun, pneumatic nozzle-mix. At least 50 ft (15.2 m) of

hose should be available. Acceptable nozzle diameters range

from 1 to 2 in. (25 to 51 mm).

4.2 Air Compressor, capable of delivering sufficient pres-

sure and volume to adequately move refractory to the gun. The

compressor should be able to supply at least 250 ft

(7 m

)/min.

4.3 Forms, suitable nonabsorbent type, which will vary in

size in accordance with the number and size of samples being

prepared, but are at minimum 12 by 12 by 4 in. (305 by 305 by

100 mm). Forms should be sized to prevent rebound entrap-

ment. The use of

⁄

-in. hardware cloth as sidewalls of the form

allows most of the rebound to pass through.

5. Procedure

5.1 Store the refractory to be gunned at 70 to 85 °F (20 to

27 °C) for 24 h prior to gunning.

5.2 Place the form against a rigid surface at an angle of 80

to 90° to the horizontal.

5.3 If recommended by the supplier, predampen the refrac-

tory by mixing with potable water in a paddle mixer for 1 to

5 min or follow manufacturer’s speciﬁc instructions. In

general, regular (dense) refractories require 2 to 4 % of

predampening water and lightweight (insulating) refractories

require 5 to 8 %.

This practice is under the jurisdiction of ASTM Committee C08 on Refractories

and is the direct responsibility of Subcommittee C08.09 on Monolithics.

Current edition approved Nov. 1, 2020. Published November 2020. Originally

approved in 1979. Last previous edition approved in 2015 as C903 – 15. DOI:

10.1520/C0903-15R20.

For referenced ASTM standards, visit the ASTM website, www.astm.org, or

contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM

Standards volume information, refer to the standard’s Document Summary page on

the ASTM website.

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.

NOTE 1—Refractories that contain a high-purity cement may beneﬁt by

aging for 5 to 10 min after dampening before gunning. This “aging”

procedure should be used if gunning without it produces excessive

rebound, dusting, or slumping.

NOTE 2—Treat refractories containing metal ﬁbers in a normal manner.

If metal ﬁbers are to be added to the gunning material, add them to the

paddle mixer before any water is introduced. The amount of ﬁber to be

added and the methods of reporting this amount shall be agreed upon by

the parties involved. To prevent clumping of the ﬁbers they should be

added slowly through a suitable screen of

⁄

-in. mesh. Fibers larger than

1 in. may require larger openings. If any predampening water is to be

added, dry mix for two to three min before adding water.

5.4 Gun the refractory into the form at a distance of 3 to 4 ft

(0.91 to 1.2 m) from gun nozzle. Hold the gun nozzle at 90° to

the form. Gunning pressures are suggested to be approximately

40 psi (276 kPa) for regular-weight refractories and approxi-

mately 20 psi (138 kPa) for insulating refractories. If more than

50 ft (15 m) of hose is used, it may be necessary to add 5 psi

(34 kPa) for each additional 50 ft. These conditions and the

amount of potable water used must be adjusted by the

nozzleman for acceptable rebound. The gunning pattern in-

volves moving the nozzle in a circular motion, back and forth

across the form, beginning at the bottom. Report any unusual

dusting, slumping, or other unique characteristics of the

refractory. The water, material, and environment temperature

shall also be reported.

NOTE 3—For referee tests all participating laboratories should agree on

a speciﬁc gun pressure and other test parameters to obtain reproducible

results. Excessive air pressures and hose lengths may cause changes in

properties of the gunned refractory especially in properties of gunned

insulating refractories.

5.5 Trim the gunned surface approximately parallel to the

back of the form. See Practice C865 for procedures concerning

the measurement of specimens.

5.6 Follow the recommended manufacturer’s curing instruc-

tions. For calcium aluminate bonds, optimum curing tempera-

ture is 90 to 95 °F (32 to 35 °C) for 24 + 0.5 h.

5.7 Cut suitably sized lamination-free specimens from the

central section. If excessive tearout of refractory grain occurs

while cutting, it may be necessary to dry the panel ﬁrst before

cutting (for example, low-cement gun mix). Cut specimen to

exclude the portion nearest the backboard to eliminate trapped

rebound. Identify the gunned face or gunning direction on each

specimen since it may inﬂuence the results of subsequent tests.

5.8 Specimens prepared according to 5.7 that will be used

for further testing shall be placed in a 150 °F oven; hold until

all specimens have been inserted. Increase temperature at a rate

of 50 °F ⁄h (28 °C ⁄h) maximum from 150 °F to between 220 to

230 °F (105 to 100 °C) and hold for at least 15 h prior to testing

or ﬁring in a prescribed manner.

5.9 Determine speciﬁc properties by selected test proce-

dures.

6. Report

6.1 Report the following information:

6.1.1 Speciﬁc predampening water content and type of

mixer,

6.1.2 Premix time,

6.1.3 Temperature of the water, refractory, and environment,

6.1.4 Aging time (if any),

6.1.5 Type of gun, length and diameter of hose,

6.1.6 Gunning pressure employed,

6.1.7 Nozzle size and type,

6.1.8 Size and type of form used,

6.1.9 Type and amount (by weight or volume) of any metal

ﬁbers added prior to gunning, and

6.1.10 Curing time, temperature and environment.

6.2 The report may also specify the amount of rebound and

any unusual gunning characteristics observed.

6.3 The report may include any other parameters agreed to

by the parties involved.

7. Keywords

7.1 gunning; predampening; rebound; specimens

ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned

in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk

of infringement of such rights, are entirely their own responsibility.

This standard is subject to revision at any time by the responsible technical committee and must be reviewed every ﬁve years and

if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards

and should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the

responsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should

make your views known to the ASTM Committee on Standards, at the address shown below.

This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,

United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the above

address or at 610-832-9585 (phone), 610-832-9555 (fax), or service@astm.org (e-mail); or through the ASTM website

(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222

Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http://www.copyright.com/

C903 − 15 (2020)

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摘要：

ASTM C903 - 15 (2020) 是一项由美国材料与试验协会发布的标准化测试方法，专门用于测定耐火材料在高温环境下的导热系数。该标准于2015年首次发布，并于2020年进行了确认更新，确保其在工业检测和材料研发中的持续有效性。标准详细规定了使用比较法测量耐火材料热传导性能的试验装置、样品制备步骤、测试条件及数据处理流程，适用于各类耐火砖、耐火浇注料及陶瓷纤维制品。通过遵循ASTM C903 - 15 (2020)，工程师和质量控制人员能够获得可靠的热导率数据，从而优化窑炉、锅炉及其他高

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