What is Witnessed Sampling and Testing?

Witnessed Sampling and Testing in the Construction Inspection Industry refers to a quality control activity where sampling personnel from the construction unit, under the supervision of qualified witnessing personnel from the construction unit or supervision unit, collect or prepare samples of test blocks, test pieces, and materials related to structural safety at the construction site. These samples are then jointly sent to a qualified testing institution for testing.

Purpose and Significance

The purpose of the witnessed sampling and testing system is to ensure the authenticity and representativeness of the samples submitted for testing, prevent fraudulent practices by the construction unit, and thus ensure the quality of the building structure. It is an important means of ensuring that inspection work is scientific, fair, and accurate, and provides direct evidence for the supervision unit's acceptance and evaluation of project quality.

Materials and Projects Involved

Witnessed sampling and testing typically involve materials and projects crucial to the structural safety of the project, including concrete test blocks, masonry mortar test blocks, steel bars and their connection joint test pieces, bricks and concrete small blocks used for load-bearing walls, cement, concrete admixtures, waterproofing materials, and other test blocks, test pieces, and materials stipulated by the state.

Key Requirements

The key requirements for witnessed sampling include:

• Witnessing Ratio: For materials related to structural safety, the witnessed sampling ratio should not be less than 30% of the specified quantity.

• Personnel Qualifications: Witnessing personnel must be professional technical personnel with relevant knowledge from the construction unit or supervision unit.

• Identification and Sealing: Samples must be identified and sealed, indicating relevant information, and jointly signed and confirmed by the witnessing personnel and sampling personnel.

• Testing Unit Qualifications: Samples must be sent to a qualified testing institution for testing.

• Responsibility: Witnessing personnel and sampling personnel are responsible for the authenticity and representativeness of the samples. The testing unit is responsible for the fairness, authenticity, and accuracy of the test report.

Process Overview

The process of witnessed sampling and testing typically includes planning, sampling under witness supervision, identifying and sealing the samples, sending the samples to a qualified testing institution, testing by the testing institution, and finally issuing a test report with a special seal. If the test results are unsatisfactory, they must be reported promptly.