Florida DOT Concrete Batchman/Operator Practice Exam

What issue can arise from an accumulation of hardened concrete in a mixer drum?

1. Enhanced mixing efficiency

2. Inadequate mixing

3. Increased wear on mixer blades

4. Improved concrete strength

The correct answer is: Inadequate mixing

The presence of hardened concrete within a mixer drum can significantly hamper the efficiency of concrete mixing. When concrete hardens, it occupies volume within the drum that would otherwise be utilized for mixing fresh ingredients. This creates an obstruction that can lead to inadequate blending of the components—cement, aggregates, and water—resulting in a less uniform mixture. Proper mixing is essential for achieving the desired consistency and properties of the concrete. If the concrete cannot move freely due to hardened accumulations, the mixing action is diminished, leading to parts of the mix potentially being too wet while others could be too dry. This inconsistency directly affects the yield and performance of the final concrete product, which may not meet the required specifications for strength and workability. While other options suggest positive impacts, they do not reflect the reality of what occurs with hardened concrete accumulation. Enhanced mixing efficiency and improved concrete strength are not outcomes of such hindrances, and while increased wear on mixer blades could indeed be a consequence, it is more of a secondary issue compared to the direct impact on mixing quality.