What is witness sampling?

Witness sampling and inspection refers to the fact that under the witness of the construction unit or the project supervision unit personnel, the on-site test personnel of the construction unit sample the test blocks, test pieces and materials involving structural safety in the project and send it to the provincial level. The above-mentioned administrative department of construction shall test the qualification appraisal and the quality and technical supervision department of its quality certification testing unit (hereinafter referred to as the “inspection unit”).

The "Sampling and Inspection Regulations for Witnessing" is explained as follows:

Witness sampling and inspection: refers to the test blocks and test pieces that are involved in the safety of the project in the construction site by the test personnel of the construction unit in accordance with the relevant technical standards and specifications of the State under the witness of the construction unit or the supervision unit personnel. The materials are sampled and sent to the testing organization that has the appropriate testing qualifications for testing.

The supervising unit seals the sample of the witness test sample, and the witness certificate is stamped on the test letter of entrustment and sent to the testing organization with the appropriate testing qualification to carry out the test.

Witness sampling means that some of the incoming materials on the construction site need to be retested (retested) in the laboratory. The test specimens used at the site must be taken for experimentation. When these samples are taken, the construction unit cannot sample the samples themselves to prevent fraud. Therefore, it is required that Party A and the supervisor present the sampling process on the spot when sampling, and send it to the laboratory for testing. It is called the witness sampling test.