Recently, the implementation rules of cement product quality supervision and spot check of Guangzhou Municipal Market Supervision and Administration (revised in August 2023) have made detailed explanations on sampling methods, inspection basis, judgment rules and matters needing attention.
1 Sampling method
1.1 Sampling
in the field of production is to randomly select recently produced products with product quality inspection certificates or other forms of qualified products from the products to be sold in enterprises. It shall be carried out
according to GB 12573-2008 Methods of Sampling Cement. The base number of random samples shall meet the requirements of sampling quantity.
Bagged cement is extracted from the trestle of the enterprise. Determine the cement with one factory number, and take the same amount of samples from more than 20 bags of bagged cement in the cement with this number. The sampling quantity is 24 kg, which is divided into two equal parts. Samples of
bulk cement shall be taken at intervals of more than 20 times within the specified ex-factory number tonnage range from the bulk warehouse unloading or cement conveying machines and tools. The sampling quantity is 24 kg, and the samples shall be divided into two equal parts. Of the two equal samples after
division, one is the inspection sample and the other is the standby sample. Take one bag for each bagged cement product with
factory number, and take a card with the same content as the bagged mark for bulk cement. The packaging bag and card shall have no missing corner, and the content of the mark shall be clear.
Random numbers can generally be generated using a random number table, random number dice, or playing cards. 1.2 Sampling
in the
circulation field shall be conducted in the form of random sampling from the products to be sold of the sampled market entities. Generally, the
random number can be generated by using a random number table or the like.
Sample quantity: 2 groups of samples are taken for each product, the first group is used for inspection, and the second group is used for sample preparation. The specific sampling quantity is as follows:
2 Inspection basis
See Table 1-2 for the inspection items and inspection method basis of this spot check. 2.1 Inspection Items
of
General Portland Cement 2.2 Inspection Items
of Masonry Cement 3 Judgment Rules
3.1 Standard
GB 175-2007 General Purpose Portland Cement
GB 6566-2010 Limit
of Radionuclides in Building Materials GB 31893-2015 Limit and Determination of Water Soluble Chromium (Ⅵ) in Cement
GB/T The
current effective enterprise standards, group standards, local standards and product express quality requirements
of 3183-2017 Masonry Cement 3.2 Judgment principle
After inspection, all the inspection items meet the standard requirements, and it is judged that the sampled products are not found to be unqualified; If any one or more of the inspection items is unqualified, the product to be sampled shall be judged as unqualified. When the product is unqualified in Class A items, it is seriously unqualified.
If the expressed quality requirements of the inspected products are higher than standard requirements on which the inspection items are based in the Detailed Rules, the judgment shall be made according to the expressed quality requirements of the inspected products.
If the expressed quality requirements of the inspected products are lower than requirements of the mandatory standards on which the inspection items are based in the Detailed Rules, they shall be judged according to the requirements of the mandatory standards.
If the expressed quality requirements of the inspected products are lower than or include the requirements of the recommended standards on which the inspection items in the Rules are based, the expressed quality requirements of the inspected products shall be used to judge, but it shall be explained in the remarks of the inspection report.
If the expressed quality requirements of the inspected products lack the mandatory standard requirements on which the inspection items in the Detailed Rules are based, the mandatory standard requirements shall be followed.
If the expressed quality requirements of the inspected products lack the requirements of the recommended standards on which the inspection items in the Detailed Rules are based, the items shall not be involved in the judgment, but shall be explained in the remarks of the inspection report.
4 Precautions
4.1 When receiving the samples, the inspection agency must carefully check whether the sample sealing sheet is complete and whether the samples are in good condition. 4.2 When there are reference method and substitution method in the
method standard, the result of reference method shall prevail when the test result is the critical value. 4.3
When the content of magnesium oxide in Portland cement and ordinary Portland cement exceeds 5%, autoclave soundness test shall be carried out. After the autoclave soundness test is qualified, the content of magnesium oxide in cement is allowed to be relaxed to 6%. 4.4
When the content of magnesium oxide in A-type slag Portland cement, pozzolana Portland cement, fly ash Portland cement and composite Portland cement exceeds 6%, the autoclave soundness test shall be carried out and qualified. 4.5
When the samples are stored improperly and get damp during the delivery process, it should be considered to take samples again. 4.6 The soundness test of the cement
shall be completed within 10 days from the date of sampling.
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