Recently, the National Standardization Management Committee officially approved and issued the National Standard Announcement No.29 of 2024, which contains 290 national standards and four important amendments. Among them, the cement industry is particularly concerned about the following standards: GB/T 45002-2024 "Determination of Water Retention of Cement Mortar", which is the first issue of the new standard and will be implemented on June 1, 2025; Amendment No.1 to the national standard GB/T 1596-2017 Fly Ash for Cement and Concrete, which will come into effect on June 1, 2025.
1. GB/T 45002-2024 "Determination of Water Retention Rate of Cement Mortar" is the first standard issued and will be implemented on June 1, 2025; Water retention rate is a very important quality index in the mortar industry, which mainly affects the construction performance of mortar. Water retention rate directly affects the plasticity and fluidity of mortar, which can effectively control the moisture content of mortar, so as to keep it in a suitable state, easy to use and improve the construction efficiency, and ensure the strength and durability of mortar products. Because the main components of mortar contain cement raw materials, and because of the improvement of national requirements for cement quality, it is necessary to issue national standards and unify the standards of determination methods. It is necessary for cement enterprises to regularly test their own factory cement according to the standards.
II. Amendment No.1 of GB/T 1596 — 2017 Fly Ash Used in Cement and Concrete mainly includes the following amendments:
1. The requirements for ammonium ions in fly ash are added. Article 6.6 is
added: the content of ammonium ion in fly ash is not more than 210 mg/kg; the content of ammonium ion inspection is included in the type inspection of Article 8.3; the requirement of ammonium ion content is added in the judgment rules of Article 8.4, and if the ammonium ion exceeds the standard, it is judged as unqualified products.
2. The sampling method of fineness is revised.
7.1 The test method for fineness shall be changed to: the test specimen shall be representative and uniform. Divide the sample to about 100 G by quartering or divider, pass the sample through a 0.9 mm square-hole sieve, remove impurities, and mix. Before determination, dry the sample in a drying oven at 105 ℃, 105 ℃ and 110 ℃ to a constant volume, cover the sample bottle, and place it in a dry exploder to cool to room temperature for determination. If the sieve residue contains more large particles or caking phenomenon, it shall be stated in the report. The fineness test was carried out according to the 45 um negative pressure sieve analysis method in GB/T1345, and the total sieve analysis time was 3 min. In the process of sieving and analysis, stop the machine for observation after sieving and analysis for 2min. If there is caking, use a spoon to gently crush the fine particles or use a brush to gently brush the fine particles, and gently knock the spoon or brush on the edge of the sieve frame to make the sample adhered to the spoon or brush fall into the sieve. Cover the sieve and continue sieving and analysis for 1min. The standard sample of fly ash fineness conforming to the provisions of GSB 08-4014 shall be used for the sieve. The sieve shall be corrected by analyzing not more than 100 samples, and the result treatment shall be the same as the provisions of GBTT 1345.
The simple understanding is to sift for two minutes, then use a brush to gently brush the caked material, and then sift for one minute.
3. Added ammonium ion detection method and standard sample.
2.1 GB/T Limitation and Test Method of Ammonium Ion Content in 39701 Fly Ash is added, "GSB 08-2506 Standard Sample of Fly Ash Fineness" is changed into "GSB 08-4014 Standard Sample of Fly Ash Physical Properties for Cement and Concrete".
Added "7.10 Ammonium ion content shall be in accordance with GB/T 39701, and can be corrected by using series standard samples of fly ash ammonium ion content conforming to GSB 08-3912 or other standard samples of the same level.".
The simple understanding is to stipulate the specific test method and new standard sample of the newly added detection method of ammonium ion in fly ash.
In general, the main reason for the addition of Amendment No.1 to GB/T 1596-2017 Fly Ash Used in Cement and Concrete is that the environmental protection policy has become stricter in recent years, and the desulfurization and denitrification process has been added to power plants, resulting in excessive ammonium ions in some fly ash on the market. Excessive ammonium ions in fly ash, whether applied to cement or concrete, will ultimately affect the concrete, on the one hand, ammonia odor appears in the construction, which will cause personal injury to the site construction personnel; II. The concrete will produce a large number of bubbles. After vibration, there are still a large number of bubbles on the surface of the concrete, which will affect the appearance of the concrete, cause poor compactness of the concrete and reduce the strength of the concrete. In order to ensure the quality of the concrete, this amendment is issued.
