This standard specifies the limit of ammonia release in concrete admixtures. This standard applies to all types of concrete admixtures for indoor use that can release ammonia, but does not apply to concrete admixtures for bridges, roads and other outdoor projects. GB 18588-2001 Limit of ammonia release in concrete admixtures GB18588-2001 standard download decompression password: www.bzxz.net

ICS 91. 100.30
National Standard of the People's Republic of China
GB185882001
Limit of ammonia emitted from the concrete admixtures2001-12-10 Issued
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
2002-01-01 Implementation
GB18588—2001
Chapter 4 of this standard is mandatory, and the rest are recommended. Appendix A of this standard is a normative appendix.
From January 1, 2002, the products produced by the production enterprises shall comply with this national standard, with a transition period of 6 months; from July 1, 2002, the products that do not meet this national standard shall be stopped from being sold on the market. This standard is proposed by China Building Materials Industry Association. This standard is under the jurisdiction of the National Technical Committee for Standardization of Cement Products. The responsible drafting unit of this standard is the Institute of Environmental Engineering, China Building Materials Science Research Institute. The participating drafting units of this standard are: Zhejiang Wulong Chemical Co., Ltd., Beijing Zhongyan Special Engineering Materials Co., Ltd., Jilin First Construction Group Co., Ltd., Beijing Urban Construction Group Component Factory, and Institute of Cement Science and New Building Materials, China Building Materials Science Research Institute. The main drafters of this standard are: Xiao Ying, Xie Yu, Song Zhihua, Ai Ping, Huang Huifang, Shen Xingen, and Nie Qing. 530
1 Scope
Limit of ammonia release in concrete admixtures
This standard specifies the limit of ammonia release in concrete admixtures. GB18588—2001
This standard applies to all types of concrete admixtures for indoor use that can release ammonia and are used in buildings, but not to concrete admixtures for bridges, roads and other outdoor projects. 2 Normative references
The clauses in the following documents become the clauses of this standard through reference in this standard. For any dated referenced document, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, parties to an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For any undated referenced document, the latest version shall apply to this standard. GB/T8075 Classification, naming and definition of concrete admixtures 3 Terms and definitions
The terms and definitions established in GB/T8075 and the following terms and definitions apply to this standard. Concrete admixtures are substances added during the mixing process of concrete to improve the performance of concrete. 4 Requirements
The amount of ammonia released in concrete admixtures is <0.10% (mass fraction). 5 Test method
5.1 Sampling and retention of samples
Randomly select 1kg sample from the admixture with the same number, mix well, and divide it into two parts, one of which is sealed and stored for three months, and the other is used as a test sample.
5.2 Test method
Follow Appendix A.
6 Inspection rules
6.1 The technical requirements listed in this standard are type inspection items. 6.1.1 Under normal production conditions, type inspection shall be carried out at least once a year. 6.1.2 Type inspection shall be carried out in the following cases: When a new product is trial-produced;
- When the product is produced in a different place;
~ When there are major changes in the production process and its raw materials; 6.2 Determination of test results
The test results are qualified if they meet the requirements of Chapter 4. 531
GB 18588—2001
A.1 Principle
Appendix A
(Normative Appendix)
Determination of released ammonia in concrete admixtures Titration after distillation Ammonia is distilled from an alkaline solution and absorbed with an excess sulfuric acid standard solution. The excess sulfuric acid is titrated with a sodium hydroxide standard titration solution using a methyl red-methylene blue mixed indicator as an indicator. A.2 Reagents
A.2.1 The water involved in this method is distilled water or water of equivalent purity. A.2.2 Unless otherwise specified, the chemical reagents involved in this method are all analytically pure chemical reagents. A.2.3 Hydrochloric acid: 1+1 solution.
A.2.4 Standard sulfuric acid solution: c(1/2H,SO.)=0.1mol/L. A.2.5 Standard sodium hydroxide titration solution: c(NaOH)=0.1mol/L. A.2.6 Methyl red-methylene blue mixed indicator solution: Mix 50mL methyl red ethanol solution (2g/L) and 50mL methylene blue ethanol solution (1g/L).
A.2.7 Wide range pH test paper.
Sodium hydroxide.
Instruments
Analytical balance: accuracy 0.001g.
500mL glass distiller.
300mL beaker.
A.3.4250mL measuring cylinder.
A.3.520ml pipette.
50mL basic burette.
1000W electric furnace.
A.4 Analysis steps
A.4.1 Sample treatment
Solid samples need to be placed in a desiccator for 24 hours before measurement, and liquid samples can be weighed directly. Stir the sample evenly, weigh two samples of about 5g each, accurate to 0.001g, put them into two 300mL beakers, add water to dissolve, if there is insoluble matter in the sample, use step A.4.1.2. A.4.1.1 Water-soluble samples
Add water to the 300mL beaker (A.3.3) containing the sample, transfer to a 500mL glass distiller (A.3.2), control the total volume to 200mL, and prepare for distillation.bZxz.net
A.4.1.2 Samples containing water-insoluble substances that may retain ammonia Add 20mL water and 10mL hydrochloric acid solution (A.2.3) to the 300mL beaker (A.3.3) containing the sample, stir evenly, let stand for 20 minutes, filter, collect the filtrate and transfer to a 500mL glass distiller (A.3.2), control the total volume to 200mL, and prepare for distillation. 532
A.4.2 Distillation
GB 18588—2001
Add several grains of sodium hydroxide (A.2.8) to the solution to be distilled, test with a wide range test paper (A.2.7), adjust the solution pH ≥ 12, and add several explosion-proof glass beads.
Accurately transfer 20mL of sulfuric acid standard solution (A.2.4) to a 250mL measuring cylinder (A.3.4), add 3~~4 drops of mixed indicator (A.2.6), and insert the glass tube of the distillate outlet of the distiller into the sulfuric acid solution at the bottom of the measuring cylinder. After checking that the distiller is connected correctly and ensuring that it is sealed, heat and distill. Stop heating after collecting 180mL of distillate, remove the distillation flask, rinse the condenser with water, and collect the washing liquid in the measuring cylinder. A, 4.3 Titration
Transfer the solution in the measuring cylinder into a 300mL beaker, wash the measuring cylinder, and add the washing liquid to the beaker. Use sodium hydroxide standard titration solution (A, 2.5) to back-titrate excess sulfuric acid standard solution until the indicator changes from bright purple to gray-green. The volume of sodium hydroxide standard titration solution consumed is Vi.
A.4.4 Blank test
At the same time as the determination, follow the same analysis steps, reagents and dosages, without adding test materials, and perform a parallel operation to determine the volume of sodium hydroxide standard titration solution consumed in the blank test (V,).
A.5 Calculation
The amount of ammonia released in the concrete admixture sample is expressed as the mass fraction of ammonia (NH:), calculated according to formula (1), Xx V. -V)c× 0. 017 03 × 100m
Where:
0. 017 03-
The amount of ammonia released from concrete admixture, in mass fraction (%); The exact value of the concentration of sodium hydroxide standard solution, in moles per liter (mol/L); The value of the volume of sodium hydroxide standard solution consumed by the titration sample solution, in milliliters (mL); The value of the volume of sodium hydroxide standard solution consumed by the blank test, in milliliters (mL); (1)
The mass of ammonia expressed in grams equivalent to 1.00mL of sodium hydroxide standard solution [c(NaOH)=1.000 mol/L]; The value of the mass of the sample, in grams (g). The arithmetic mean of the results of two parallel determinations is taken as the determination result. When the absolute difference between the results of two parallel determinations is greater than 0.01%, re-determination is required.
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