ASTM C1240-20

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
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Designation: C1240 − 15 C1240 − 20
Standard Specification for
Silica Fume Used in Cementitious Mixtures
This standard is issued under the fixed designation C1240; 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 Scope*
1.1 This specification covers silica fume for use in concrete and other systems containing hydraulic cement.
1.2 In the cases of slurried or densified silica fume, perform the tests on the raw silica fume from which these products have
been made.
1.3 The units stated in SI are to be regarded as the standard. No other units of measurement are included in this standard.
1.4 The following safety hazards caveat pertains only to the test methods portions, Sections 10 – 19, of this specification: 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 appropriate safety safety, health, and healthenvironmental practices and determine the applicability
of regulatory limitations prior to use. Read the material safety data sheets for materials used.
1.5 The text of this standard references notes and footnotes that provide explanatory information. These notes and footnotes
(excluding those in tables) shall not be considered as requirements of this standard.
1.6 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.
2. Referenced Documents
2.1 ASTM Standards:
C109/C109M Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or [50-mm] Cube Specimens)
C114 Test Methods for Chemical Analysis of Hydraulic Cement
C125 Terminology Relating to Concrete and Concrete Aggregates
C135 Test Method for True Specific Gravity of Refractory Materials by Water Immersion
C183C183/C183M Practice for Sampling and the Amount of Testing of Hydraulic Cement
C185 Test Method for Air Content of Hydraulic Cement Mortar
C219 Terminology Relating to Hydraulic and Other Inorganic Cements
C311/C311M Test Methods for Sampling and Testing Fly Ash or Natural Pozzolans for Use in Portland-Cement Concrete
C430 Test Method for Fineness of Hydraulic Cement by the 45-μm (No. 325) Sieve
C441/C441M Test Method for Effectiveness of Pozzolans or Ground Blast-Furnace Slag in Preventing Excessive Expansion of
Concrete Due to the Alkali-Silica Reaction
C494/C494M Specification for Chemical Admixtures for Concrete
C604 Test Method for True Specific Gravity of Refractory Materials by Gas-Comparison Pycnometer
C670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
C1005 Specification for Reference Masses and Devices for Determining Mass and Volume for Use in the Physical Testing of
Hydraulic Cements
C1012/C1012M Test Method for Length Change of Hydraulic-Cement Mortars Exposed to a Sulfate Solution
C1069 Test Method for Specific Surface Area of Alumina or Quartz by Nitrogen Adsorption
C1157/C1157M Performance Specification for Hydraulic Cement
C1437 Test Method for Flow of Hydraulic Cement Mortar
This specification is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee C09.24 on
Supplementary Cementitious Materials.
Current edition approved June 15, 2015Jan. 15, 2020. Published September 2015March 2020. Originally approved in 1993. Last previous edition approved in 20142015
as C1240 – 14.C1240 – 15. DOI: 10.1520/C1240-15.10.1520/C1240-20.
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.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1240 − 20
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this specification, refer to Terminology C125 and Terminology C219.
3.2 Definitions:Definitions of Terms Specific to This Standard:
3.1.1 silica fume, n—very fine pozzolanic material, composed mostly of amorphous silica produced by electric arc furnaces as
a by-product of the production of elemental silicon or ferro-silicon alloys (also known as condensed silica fume and microsilica).
3.2.1 silica fume, densified, n—silica fume processed to increase bulk density to facilitate handling and shipping.
3.2.2 silica fume, undensified, n—silica fume in its raw, as produced or as collected, unprocessed form.
3.1.4 Other terms in this specification are defined in Terminologies C125 and C219.
4. Ordering Information
4.1 The purchaser shall specify any optional chemical or physical requirements.
5. Chemical Composition
5.1 Silica fume shall conform to the requirements for chemical composition prescribed in Table 1.
6. Physical Requirements
6.1 Silica fume shall conform to the physical requirements prescribed in Table 2. Optional physical requirements are given in
Table 3.
7. Sampling
7.1 WhenIf the purchaser desires that the silica fume be sampled and tested to verify compliance with this specification, perform
the sampling and testing in accordance with Practice C183C183/C183M, modified as described in 7.3.
NOTE 1—Exercise caution in the interpretation of Practice C183C183/C183M, since there is a difference between the continuous manufacture of
hydraulic cement and the generation and collection of silica fume. To a great extent, storage is dictated by the design of the silica-fume collection system.
The design of silica-fume collection systems may not have provided for sampling points and practices.
7.2 Practice C183C183/C183M, as modified, is not designed for manufacturing quality control and is not required for
manufacturer’s certification.
7.3 The following modification of Practice C183C183/C183M is necessary to render it applicable to silica fume.
7.3.1 Replace the words “hydraulic cement” and “cement” with the words “silica fume” every time that they appear in the text.
7.3.2 All samples, whether grab or composite, shall have a mass of at least 1 kg.
7.3.3 WhenIf compliance verification tests of silica fume are required to be made at a laboratory other than that of the
silica-fume manufacturer or marketer, coordinate the silica-fume sampling schedule, sample transportation time, and sample
testing schedule among the purchaser, manufacturer, and testing laboratory so that the test results will be available when the
decision to accept or reject the silica fume must be made.
7.3.4 The section entitled “Sampling” is modified as follows:
7.3.4.1 Take two grab samples or two composite samples for the first 100 Mg of silica fume. Take a grab sample or a composite
sample for each subsequent 100 Mg of silica fume, but not less than two samples shall be taken in any sampling program.
7.3.4.2 From Bulk Storage at Points of Discharge—Withdraw silica fume from the discharge openings in a steady stream until
sampling is completed. In sampling bulk storage at points of discharge, while the silica fume is flowing through the openings, take
samples at such intervals so that, at a minimum, the sampling requirements of 7.3.4.1 are met.
7.3.5 The section entitled “Amount of Testing” is modified by deleting the first paragraph, “General.”
8. Frequency of Tests
8.1 Except for the tests listed in 8.2, make all chemical determinations and physical tests on composite samples representing
no more than 400 Mg each. Prepare each composite sample by combining portions from the samples representing each 100 Mg,
so that each 100 Mg is represented equally.
8.2 Test for specific surface, density, and accelerated pozzolanic strength activity index using composite samples that represent
3200 Mg or three months of production, whichever gives the highest frequency. Prepare each composite sample by combining
portions from the samples representing each 400 Mg or 1 month, whichever gives the highest frequency, so that each sample is
represented equally.
TABLE 1 Chemical Requirements
SiO , min, % 85.0
Moisture content, max, % 3.0
Loss on ignition, max, % 6.0
C1240 − 20
TABLE 2 Physical Requirements
Oversize:
A
Percent retained on 45-μm (No. 325), max, % 10
Percent retained on 45-μm (No. 325), max variation from 5
B
average, percentage points
C
Accelerated pozzolanic strength activity index:
With portland cement at 7 days, min percent of control 105
Specific surface, min, m /g 15
A
Exercise care to avoid retaining agglomerations of extremely fine material.
B
The average shall consist of the ten preceding tests or all of the preceding tests
if the number is less than ten.
C
Accelerated pozzolanic strength activity index is not to be considered a measure
of the compressive strength of concrete containing the silica fume. This is a
measure of the reactivity of a given silica fume with a given cement and may vary
with the source of both the silica fume and the cement.
A
TABLE 3 Optional Physical Requirements
Uniformity requirements:
When air-entraining concrete is specified, the quantity of air- 20
entraining agent required to produce air content of 18.0 vol %
of mortar shall not vary from the average established by the ten
preceding tests or by all preceding tests if less than ten, by
more than, %
If air-entraining concrete is specified, the quantity of air-entraining 20
agent required to produce air content of 18.0 vol % of mortar
shall not vary from the average established by the ten
preceding tests or by all preceding tests if less than ten, by
more than, %
B
Reactivity with cement alkalies:
Reduction of mortar expansion at 14 days, min, % 80
C
Sulfate resistance expansion,
(moderate resistance) 6 months, max, % 0.10
(high resistance) 6 months, max, % 0.05
(very high resistance) 1 year, max, % 0.05
A
Will be made only at the request of the purchaser.
B
The indicated tests for reactivity with cement alkalies shall not be requested
unless the material is to be used with an aggregate that is regarded as
deleteriously reactive with alkalies in hydraulic cement. The test for reduction of
mortar expansion may be made using any high-alkali cement in accordance with
Test Methods C311/C311M, if the cement to be used in the work is not known or
is not available at the time of the test. The test for mortar expansion should be
performed by each of the high-alkali cements to be used in the work.
C
Only one limit shall be specified.
9. Preparation of Sample
9.1 Prepare composite samples for tests, as required in Section 8, by arranging all test samples in groups, with each group
representing the number of megagrams required by the test or tests for which the composite sample is intended. From each of the
samples in a group, take equal portions, sufficient in amount to form a composite sample large enough to permit making the
required physical or chemical determinations.
9.2 Prior to testing, mix grab samples and composite samples thoroughly. A clean and dry laboratory concrete drum mixer
provides adequate mixing for this purpose. Take care to limit the volume of silica fume in the drum mixer to the range of 10 to
50 % of the drum’s total capacity. If necessary, secure a sheet of polyethylene film on the drum with an elastic tiedown to keep
the material in the drum. Limit the mixing action to 5 6 1 min.
9.2.1 WhenIf a small sample size precludes the use of a concrete mixer, use a heavy plastic bag, of a capacity at least five times
larger than the sample volume, to mix the sample thoroughly. After placing the sample in the bag, close the bag by tying the bag
opening tightly, and mix the material by rolling the bag around for 5 6 1 min.
9.3 Take material for specific tests from a thoroughly mixed sample by using a sampling device (sampling tube, scoop, and so
forth) of appropriate size to make a test specimen. Make this test specimen from at least six random subsamples.
TEST METHODS—CHEMICAL ANALYSIS
10. Silicon Dioxide and Total Alkalies
10.1 Reference Method—Use the reference method in Test Methods C114 for cements with insoluble residue greater than 1 %.
Analysts performing sodium oxide and potassium oxide determinations shall observe the precautions outlined in the applicable
section of Performance Specification C1157/C1157M (refer to the section on Test Methods). Most pozzolans dissolve completely
in lithium borate fluxes.
C1240 − 20
11. Moisture Content and Loss on Ignition
11.1 Follow the applicable provisions of Test Methods C311/C311M.
TEST METHODS—PHYSICAL TESTS
12. Density
12.1 Determine density using either Test Method C135 as modified in 12.1.1 or Test Method C604.
12.1.1 Test Method C135 modified as follows:
12.2 Equipment:
12.2.1 Two 500-mL Volumetric Flasks, Class A.
12.2.2 Balance, with an accuracy of at least 0.01 g.
12.2.3 Constant Temperature Bath, capable of being regulated within 60.5 °C.
12.3 Deionized Water.
12.4 Procedure:
12.4.1 Determine the density of the material as received, unless otherwise specified, as follows. If density determination on an
ignited sample is required, first ignite the sample as described in the test for loss on ignition in the applicable section given in Test
Methods C114.
12.4.2 Determine the mass (W ), of a 500-mL volumetric flask, to an accuracy of 0.01 g. Add 30 g of silica fume. Determine
f
the mass of the flask and the contents (W ) to the nearest 0.01 g. Add water to the flask to fill it one-half full, and shake it to ensure
a
thorough wetting of the material. Fill to the mark with water. Remove air bubbles by shaking the flask at 15-min intervals until
the liquid is free of air or by applying a vacuum to the flask. After all of the air bubbles are removed, place the flask in a constant
temperature bath at 23 6 0.5 °C until the flask and its contents reach a constant temperature. Remove the flask from the water bath;
immediately add or remove water, at the same temperature, to the flask to get the meniscus on the mark. Wipe dry the exterior of
the flask and determine the mass of the flask and its contents (W ).
s
12.4.3 Empty, clean, and determine the mass of the 500-mL volumetric flask, used above, filled to the mark with water (W )
t
stabilized at 23 6 0.5 °C.
12.5 Calculation:
~W 2 W !
a f
D 5 (1)
sf
500 mL 2 W 2 W /D
@~ ! #
s a w
where:
D = density of silica fume, Mg/m ,
sf
W = mass of 500-mL volumetric flask, g,
f
W = mass of 500-mL volumetric flask plus approximately 30 g of silica fume, g,
a
W = mass of 500-mL volumetric flask plus silica fume plus water to the mark, g,
s
W = mass of 500-mL volumetric flask plus water to the mark, g, and
t
D = (W − W )/500-mL, Mg/m .
w t f
12.6 Report the average of two density determinations and the test method used in determining the density.
13. Oversize, Amount Retained When Wet-Sieved on a 45-μm (No. 325) Sieve
13.1 Use Test Method C430. CalibrateStandardize the sieves in accordance with Test Method C430.
NOTE 2—Oversize is used to determine the amount of contaminating material retained on the 45-μm sieve. See Appendix X2.
14. Specific Surface
14.1 Determine the specific surface
...