GB/T 21371-2019 English PDF (GBT21371-2019)

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GB/T 21371-2019: By-product gypsum used in cement
GB/T 21371-2019
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 91.100.10
Q 11
Replacing GB/T 21371-2008
By-Product Gypsum Used in Cement
ISSUED ON: OCTOBER 18, 2019
IMPLEMENTED ON: SEPTEMBER 01, 2020
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative References ... 5
3 Terms and Definitions ... 5
4 Technical Requirements ... 6
5 Test Methods ... 7
6 Judgment Rules ... 8
7 Transportation and Storage ... 9
By-Product Gypsum Used in Cement
1 Scope
This Standard specifies the terms and definitions, technical requirements, test methods and
judgment rules, transportation and storage of industrial by-product gypsum used in cement.
This Standard is applicable to the acceptance and use of industrial by-product gypsum for
adjusting the setting time of cement.
2 Normative References
The following documents are essential to the application of this document. For the dated
documents, only the versions with the dates indicated are applicable to this document; for the
undated documents, only the latest version (including all the amendments) is applicable to this
document.
GB/T 1346 Standard Test Method for Water Requirement for Normal Consistency Setting
Time and Soundness of the Portland Cement
GB/T 2419 Test Method for Fluidity of Cement Mortar
GB/T 5483 Natural Gypsum
GB/T 5484 Methods for Chemical Analysis of Gypsum
GB 6566 Limit for Radionuclides in Building Materials
GB/T 17671 Test Method of Cement Mortar Strength (ISO Method)
JC/T 1083 Test Method for Compatibility of Cement and Water-Reducing Agent
3 Terms and Definitions
For the purposes of this Document, the following terms and definitions apply.
3.1 By-product gypsum
The general term for by-products with calcium sulfate as the main component that are
discharged from industrial manufacturing.
NOTE 1: Also known as chemical gypsum, synthetic gypsum.
S – mass fraction of SO3, expressed by percentage (%);
w – mass fraction of crystal water, expressed by percentage (%).
5.3 Radioactive material limits
It shall be tested according to GB 6566.
5.4 Influence of industrial by-product gypsum on cement properties
5.4.1 Preparation of contrast cement
It is the P·I Portland cement, which is prepared by the Category-G and Class-2 above (including
Class-2) gypsum specified in GB/T 5483, with SO3 content of 2.0%~2.5%, 80μm sieve residue
of less than 4%, and specific surface area of 350m2/kg±10m2/kg.
5.4.2 Preparation of test cement
It is P·I Portland cement that is prepared by using Portland cement clinker for preparing contrast
cement and by replacing natural gypsum with 30%~100% of the assessed industrial by-product
gypsum. During the preparation, the 80μm sieve residue of the cement shall be controlled to
less than 4%, the specific surface area shall be within the range of 350m2/kg ± 10m2/kg, and
the difference between the SO3 content and the contrast cement SO3 content shall be within
0.2%.
5.4.3 Standard consistency water consumption, setting time and stability of cement
It shall be tested according to GB/T 1346.
5.4.4 Fluidity of cement mortar
The preparation of cement mortar is carried out according to GB/T 17671; and the fluidity test
operation of cement mortar is carried out according to GB/T 2419.
5.4.5 Strength of cement mortar
It shall be tested according to GB/T 17671.
5.4.6 Compatibility of cement and water-reducing agent
It shall be tested according to JC/T 1083.
6 Judgment Rules
When any one of 4.1, 4.3, 4.4, 4.5 and 4.6 does not meet the requirements of this Standard, it
cannot be used in the manufacturing of cement.