1. Basic Performance Testing of Water-Reducing Agents
This involves evaluating the physicochemical properties of the water-reducing agent itself to ensure it meets basic quality requirements.

1) Appearance and Physical Properties: Check the color, form (liquid or powder), and uniformity of the water-reducing agent. Liquid products should be free of stratification and sedimentation, and powders should be free of lumps. Simultaneously measure density, viscosity, and pH value to assess the suitability of its concentration and acidity/alkalinity.

2) Chemical Composition Analysis: Detect the content of the main active ingredients (such as polycarboxylic acids, naphthalene-based compounds, etc.) using methods such as high-performance liquid chromatography (HPLC), and strictly control chloride ion and alkali content to prevent steel corrosion or alkali-aggregate reaction. 2. Tests on the Impact of Water-Reducing Agents on Concrete Workability
These experiments directly verify the ability of water-reducing agents to improve the workability of concrete.

1) Water Reduction Rate Determination: Under the condition of maintaining a constant concrete slump, the percentage reduction in unit water consumption before and after adding the water-reducing agent is compared. This is the core indicator for measuring the water-reducing effect.

2) Slump and Slump Retention: The initial slump of the concrete and the slump loss over a certain period of time are measured to ensure that the water-reducing agent can effectively maintain the fluidity of the concrete and meet the requirements of construction operations.

3) Air Content Detection: The air bubble content introduced into the concrete by the water-reducing agent is measured. For air-entraining water-reducing agents, the air content needs to be controlled within a reasonable range (e.g., ≤3.0%) to avoid affecting the density of the concrete.

3. Evaluation of the Impact of Water-Reducing Agents on Concrete Strength and Durability
These experiments evaluate the contribution of water-reducing agents to the long-term performance of concrete.

1) Compressive Strength Ratio Test: After standard curing, the compressive strength of concrete is measured at 3 days, 7 days, and 28 days. The strength ratio is calculated to that of the reference concrete to ensure that the water-reducing agent does not reduce the concrete strength.

2) Durability Test: This includes freeze-thaw cycle tests (to assess strength retention), impermeability tests (to test density), and carbonation resistance tests (to assess long-term durability) to verify the adaptability of the water-reducing agent to concrete in harsh environments.

4. Compatibility and Stability Tests: These tests ensure that the water-reducing agent can be well-matched with local cement, admixtures, and other materials.

1) Compatibility Test: The water-reducing agent is mixed with different brands of cement or admixtures to observe whether segregation, bleeding, or excessive retardation occurs, avoiding construction problems.

2) Stability Test: The performance stability of the water-reducing agent during storage or use is evaluated, such as whether the solid content and viscosity change over time. 5. Environmental Protection and Safety Performance Testing
Modern engineering increasingly emphasizes the environmental impact of water-reducing agents.

1) Hazardous Substance Testing: Analyzing the content of harmful substances such as formaldehyde and heavy metals in water-reducing agents to ensure compliance with environmental standards.

2) Biodegradability: For specific projects, it may be necessary to test the biodegradability of water-reducing agents to reduce environmental burden.

In actual engineering, these experiments must be conducted according to national standard methods, and test blocks must be cured under constant temperature and humidity conditions to ensure the reliability of the results. Concrete mixing plants typically need to regularly test key indicators such as bleeding rate and air content as a basis for selecting water-reducing agent brands.

What is the role of test blocks in concrete experiments?

In concrete experiments, test blocks mainly play a crucial role in evaluating and controlling concrete quality. Specific functions include the following:

1. Strength Verification: Through compressive strength testing, determining whether the concrete meets the design strength standards is fundamental to ensuring structural safety. 2. Quality Control: Test blocks are used to monitor the entire construction process (such as batching, mixing, vibration, and curing) to promptly identify and correct problems (such as segregation, honeycombing, and surface roughness) and ensure the uniformity and stability of the concrete.

3. Acceptance Basis: Standard-cured test blocks are used for project acceptance to assess whether the concrete mix proportions meet the specifications; test blocks cured under the same conditions reflect the strength development of the actual structure and serve as the basis for decision-making in key processes such as formwork removal and prestressing.

4. Problem Tracing and Handling: When concrete quality fails to meet standards, test block data can help pinpoint the problem area (such as improper mix proportions or insufficient curing) and guide remedial measures (such as remaking test specimens or structural testing).

Test blocks are typically made according to standard methods (such as cubic shape, with sides of 15 cm or 20 cm) and strictly cured to ensure the accuracy and representativeness of the test results. In actual projects, a sufficient number of test blocks must be retained according to specifications to meet statistical evaluation requirements.