Which statement about ready-mix concrete is correct?

• A. Ready-mix provides centralized batching with QA/QC; site-mixed is generally less controlled with greater variability.
• B. Site-mixed always achieves higher strength.
• C. QA/QC is not required for ready-mix.
• D. There is no difference in quality control.

Answer: (A)

Ready-mix concrete comes from a plant where materials are batched precisely and mixed under controlled conditions, with QA/QC checks to verify each batch meets the specified performance. This centralized batching and testing ensure consistent strength, workability, and air content from one delivery to the next, and it helps manage temperature and curing considerations so the concrete behaves predictably on site.

Site-mixed concrete, by contrast, is mixed on the job site with looser control over proportions, mixing time, and conditions. Small errors in measuring materials, variations in mixing efficiency, and on-site adjustments (like adding extra water) introduce greater variability in the final strength and performance.

That’s why the statement highlighting centralized batching with QA/QC for ready-mix, and less control and more variability for site-mixed, is the accurate one. The other choices contradict common practice: QA/QC is essential for ready-mix; site-mixed does not reliably guarantee higher strength; and there is a measurable difference in quality control between the two.