Which components of the delivery system are most critical in preventing segregation during discharge?

• A. The water system and engine horsepower
• B. The driver’s training and truck color
• C. The mixing drum with proper blade action, uniform rotation, and the discharge chute/gate
• D. The concrete supplier's location

Answer: (C)

The key idea is keeping the concrete uniformly mixed up to the moment it leaves the truck and controlling how it flows out. The mixing drum does the essential work: with proper blade action, it mechanically shears and re-suspends the aggregates so the paste and aggregates stay evenly distributed. When the drum rotates uniformly, there are no stagnant areas, so heavier pieces don’t settle out or separate from the rest of the mix as it moves toward the discharge.

The discharge path—specifically the chute or gate—is critical to how the mix exits. A well-designed chute and properly adjusted gate shape and control the flow rate, reducing turbulence and avoiding velocity differences that can cause segregation. This keeps the mix flow steady and uniform as it leaves the truck, which is essential for consistent placement.

Other aspects listed don’t directly affect how the concrete behaves during discharge. The water system and engine horsepower influence pumping or mobility, not the likelihood of segregation once the concrete is in motion. Driver training and truck color don’t impact the physical separation of materials, and the supplier’s location isn’t a factor in how the mix discharges.