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This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard was proposed by China Building Materials Federation.
This standard is under the jurisdiction of SAC/TC 195 National Technical Committee on Lightweight and Decorative Building Materials of Standardization Administration of China.
Introduction
The issuing body of this document draws attention to the fact that claims of compliance with this document may involve the use of a patent in ZL 2011 10033606.1 Method for quickly analyzing phase composition of calcined gypsum.
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Name of patent holder: Shanghai Research Institute (Group) of Building Sciences Co., Ltd.
Address: No. 75, Wanping South Road, Xuhui District, Shanghai
http://www.jk.sh.cn/
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Methods for phase composition analysis of calcined gypsum
1 Scope
This standard specifies the oven method and moisture analyzer method for phase composition analysis of calcined gypsum.
This standard is applicable to the analysis of content of three phases, namely soluble anhydrite (AIII), hemihydrate gypsum (HH) and dihydrate gypsum (DH) in calcined gypsum powder prepared by calcination of dihydrate gypsum (natural gypsum or industrial by-product gypsum).
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 6682 Water for analytical laboratory use - Specification and test methods
3 Principle
3.1 Soluble anhydrite (AIII) in calcined gypsum
Soluble anhydrite (AIII) is hygroscopic and may convert to hemihydrate gypsum (HH) by absorbing water in the air, so soluble anhydrite (AIII) and attached water will not be present in the sample at the same time. Soluble anhydrite (AIII) can be hydrated to hemihydrate gypsum in 95% aqueous ethanol, but under the same conditions hemihydrate gypsum (HH) cannot be hydrated to dihydrate gypsum (DH), so the content of the soluble anhydrite (AIII) may be calculated by determining the increment of dydrated soluble anhydrite in 95% aqueous ethanol. The hydration reaction formula is as follows:
CaSO4+0.5H2O=CaSO4·0.5H2O
Calculate the content of soluble anhydrite (AIII) using the chemical reaction formula.
If no soluble anhydrite (AIII) is present in the sample, the mass fraction of the attached water may be calculated based on the mass by which the sample mass before drying is greater than that after constant weight drying.
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3.2 Hemihydrate gypsum (HH) in calcined gypsum
Hemihydrate gypsum (HH) and soluble anhydrite (AIII) may all be hydrated to dihydrate gypsum (DH) in pure water, and the content of dihydrate gypsum (DH) may be calculated by determining the increment of calcined gypsum due to hydration in pure water, i.e., determining the total amount of dihydrate gypsum (DH) fromed by hemihydrate gypsum (HH) and soluble anhydrite (AIII), minus the content of soluble anhydrite (AIII) determined by the principle in 3.1 (where there is no anhydrite (AIII) phase, the mass loss due to drying of attached water shall be added). The hydration reaction formula is as follows:
CaSO4·0.5H2O+1.5H2O＝CaSO4·2H2O
CaSO4+2H2O=CaSO4·2H2O
3.3 Residual dihydrate gypsum (DH) in calcined gypsum
When calcined gypsum is heated to 200°C or above, dihydrate gypsum (DH) is dehydrated into soluble anhydrite (AIII), and the total amount of dehydration is the sum of those of dihydrate gypsum (DH), hemihydrate gypsum (HH) and attached water, which subtract the dehydration of hemihydrate gypsum (HH) and attached water is the content of residual dihydrate gypsum (DH). The thermal dehydration reaction formula is as follows:
CaSO4·2H2O CaSO4+2H2O
CaSO4·0.5H2O CaSO4+0.5H2O
4 Reagents and materials
In the analysis, Class-III water or above according to GB/T 6682 shall be used, and the ethanol solution shall be analytical reagent with a concentration of 95%.
5 Apparatus
5.1 Electronic balance, with a division of 0.0001 g.
5.2 electrically heated drying oven (baking oven), with the temperature capable of reaching 230℃ and temperature controlling accuracy of ±3℃, and equipped with automatic temperature controller.
5.3 Moisture analyzer, with a division of not less than 0.001g; usage temperature control range: 50℃~200℃; temperature control accuracy: ±1℃.
5.4 Vessel: weighing bottle with cover, with specification of Φ50 mm×30 mm.
5.5 Desiccator: contained with dried color changing silica gel.
6 Test conditions
The temperature and relative humidity of the laboratory shall be 23℃±2℃ and 50%±5%, respectively.
7 Sampling and preparation of specimens
The sample shall be taken quickly by quartering method, the amount of sample shall be about 150 g, which is put into the dried ground bottle, tightly closed, and put into the desiccator for 24 h and then immediately carried out the test.
For the test, control the weighing time within 2 min, put the remaining sample back into the desiccator immediately after covering.
Foreword i
Introduction ii
1 Scope
2 Normative references
3 Principle
4 Reagents and materials
5 Apparatus
6 Test conditions
7 Sampling and preparation of specimens
8 Oven method (Method A)
9 Moisture analyzer method (Method B)
10 Test report
