What additive should be added to concrete to make it pump easier?

• A. Hydrated lime
• B. Portland cement
• C. Fly ash
• D. Water

Answer: (A)

To enhance the performance of concrete during pumping, a common additive is hydrated lime. Hydrated lime serves as a filler and can improve the workability and cohesiveness of the concrete mix. This helps to prevent separation of the aggregate and the cement paste, allowing for a smoother flow through the pumping system.

While other additives such as water can make concrete more fluid, simply adding more water can also compromise the strength and durability of the concrete. Portland cement is the primary binding agent in concrete but does not specifically improve pumpability on its own. Fly ash is used as a supplementary cementing material that can enhance certain properties of concrete, like strength and durability, but it does not directly aid in pumping.

Using hydrated lime is particularly effective as it modifies the rheological properties of the concrete, reducing resistance as it flows through pumps, ensuring that it can be transported more easily and efficiently without compromising the final product.