When must concrete samples from a truck mixer be obtained in relation to the addition of water or admixtures?

Obtaining concrete samples from a truck mixer before any additions of water or admixtures is critical to ensure the integrity and representativeness of the sample. This procedure allows for accurate testing and evaluation of the concrete's initial properties without the influence of additional materials that could alter its composition, water-to-cement ratio, and overall performance characteristics.

Sampling at this stage provides a baseline that reflects the concrete mix as designed, which is essential for quality control and compliance with specified requirements. Testing samples obtained after additions could yield results that do not accurately represent the original mix, leading to misunderstandings about the concrete's performance and potentially compromising structural integrity.