Quality control in construction management is a crucial aspect to ensure that the construction project meets the required standards and specifications. It involves various activities such as sampling, examination, field testing, skill levels of labor, testing specimens in the laboratory, and measurement and proportioning of materials.

1. Sampling, examination, and field testing of all materials of construction:
- This step involves taking samples of various construction materials, such as concrete, steel, aggregates, etc., from different sources or batches. These samples are then examined and tested to ensure that they meet the specified requirements and standards.
- For example, concrete samples may be tested for compressive strength, workability, and durability. Steel samples may undergo tests for tensile strength and chemical composition.
- Field testing involves performing tests on-site to verify the quality of materials during construction. This may include conducting slump tests for concrete, moisture content tests for aggregates, or checking the dimensions of structural elements.

2. Skill levels of labor:
- The skill levels of the labor force involved in construction play a significant role in ensuring quality control. Adequately trained and skilled workers are essential to carry out construction activities accurately and efficiently.
- Skilled laborers are knowledgeable about construction techniques, proper handling of materials, and adherence to safety guidelines. Their expertise helps in minimizing errors and maintaining the desired quality.

3. Testing the specimens in the laboratory:
- Some construction materials require laboratory testing to ensure their quality and adherence to standards. Samples collected from the construction site are taken to the laboratory for comprehensive analysis.
- Testing in the laboratory allows for more detailed and accurate assessments of material properties. It helps in identifying any defects, impurities, or deviations from the specified requirements.

4. Measurement and proportioning of materials:
- Accurate measurement and proportioning of construction materials are crucial for achieving the desired quality in the final product. This includes ensuring the correct ratios of cement, aggregates, water, and other components in concrete mixes, as well as proper sizing and placement of structural elements.
- Deviations in material proportions can lead to issues such as reduced strength, poor workability, or inadequate durability. Therefore, careful measurement and proportioning are essential to ensure quality control.

In conclusion, quality control in construction management is ensured through a combination of sampling, examination, field testing, labor skill levels, laboratory testing, and accurate measurement and proportioning of materials. These activities help in identifying any deviations or defects in construction materials and ensure that the final product meets the required standards and specifications.