It is true or false that concrete samples from a truck mixer must be obtained before water or admixtures are added at the job site?

The assertion is true because obtaining concrete samples from a truck mixer prior to the addition of water or admixtures is essential for ensuring accurate testing and assessment of the material's properties. When concrete is mixed, its characteristics—including strength, workability, and setting time—are determined by the specific blend of materials used during the mixing process.

If water or admixtures are added at the job site, this can alter the original mix design, potentially affecting the concrete's performance. It is crucial that the samples taken for testing reflect the actual mix being used, which means they must be collected before any modifications are made. This practice helps maintain the integrity of testing procedures, ensuring that the results accurately reflect the intended concrete properties as specified in project designs and standards.

This procedure is particularly important in quality assurance and quality control processes within the construction industry where adherence to specifications is critical for safety and durability.