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

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

• A. Crushed Gravel
• B. #57 Gravel
• C. Sand
• D. Hydrated Lime

Answer: (D)

The key idea here is pumpability, which comes from how workable and flowable the concrete paste is. Hydrated lime acts as a plasticizing extender in the mix, making the cement paste smoother and more lubricious. This improves the concrete’s workability so it can flow more easily through a pump and hose without needing extra water that would weaken the mix. In practice, adding hydrated lime reduces friction within the paste and around aggregates, helping it move through the pumping system more readily. The other options are mostly aggregates. Adding more crushed gravel, #57 gravel, or sand changes the size distribution and internal friction of the mix and can increase the risk of blockages or segregation in a pump line, rather than making pumping easier. Hydrated lime is the additive that commonly improves pumpability in this context, even though it changes strength and curing characteristics.

The key idea here is pumpability, which comes from how workable and flowable the concrete paste is. Hydrated lime acts as a plasticizing extender in the mix, making the cement paste smoother and more lubricious. This improves the concrete’s workability so it can flow more easily through a pump and hose without needing extra water that would weaken the mix. In practice, adding hydrated lime reduces friction within the paste and around aggregates, helping it move through the pumping system more readily.

The other options are mostly aggregates. Adding more crushed gravel, #57 gravel, or sand changes the size distribution and internal friction of the mix and can increase the risk of blockages or segregation in a pump line, rather than making pumping easier. Hydrated lime is the additive that commonly improves pumpability in this context, even though it changes strength and curing characteristics.