Variety, representative batch, inspection items, sampling quantity, etc. Construction witness sampling.

Code for Acceptance of Construction Quality of Concrete Structure Engineering (GB50204-2002) has made it clear that local quality and safety supervision stations also have relevant regulations. Such as: cement, quantity to be delivered, location of use, representative quantity of sampling, including bulk packaging and bagging. The quantity, specification and grade of steel bars, parts used and sampling representatives shall be clearly distinguished. Welded joints and so on.

1, concrete and mortar

According to the gravel or pebble sieve analysis, the maximum particle size such as silt content and needle content is 3 1.5MM and not less than 50KG；; The maximum particle size is 40MM, not less than 60KG.

Uniformly distributed at the top, middle and bottom of the pile in different parts of 15. Take 15 roughly equal stones (remove the surface) to form a group of samples. 400M3 or 600T from the same place of origin, same specification and entering the site at the same time shall be regarded as an acceptance batch. The insufficient part is counted as a batch. If the inspection is unqualified, double sampling should be taken and the unqualified items should be reinspected.

Step 2 be specific

Mix design cement, sand, gravel are not less than 30 kg, 50 kg, 70 kg respectively. If you need to use additives or admixtures, you should send them together according to the expected dosage. ? Compressive strength: three test blocks in each group. When pouring concrete on site, random samples shall be taken, and each group of test blocks shall be sampled from the same plate of concrete.

3. Reinforcement for concrete: hot-rolled ribbed reinforcement: tensile tests such as yield point, tensile strength, elongation and cold bending performance. Bend two bars, cut two samples of 400MM and 600MM from each bar, and stretch and bend them respectively.

Extended data:

(1) witness sampling involves three parties: the constructor, the witness and the tester.

(2) Laboratory qualification management:

① Engineering quality supervision and inspection institutions at all levels (stamped with CMA seal, i.e. metrological certification, and reviewed once every 1 year).

(2) Construction enterprise laboratory-gradually transformed into enterprise internal control organization, 4 years 1 comment. (Not belonging to a third-party laboratory)

Third-party laboratory inspection:

(1) measurement certificate, CMA seal.

② Check the attachment and record the certificate.

CMA (China Metrology Certification/Accreditation) is a product quality inspection institution that provides fair data for the society according to the Metrology Law of People's Republic of China (PRC) and the National Metrology Law. Measurement certification is implemented at two levels: the first level is the national level, which is organized and implemented by the National Certification and Accreditation Administration Committee, and the first level is the provincial level, with the same effectiveness.

The witness must obtain the witness certificate and be authorized by the owner before undertaking the witness work of the authorized project. All building materials entering the construction site must undergo witness sampling and ex-factory test according to the specification requirements, and the test report should be included in the quality assurance data.

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