Excessive slump loss during concrete pumping is an indicator of?

Excessive slump loss during concrete pumping is an indicator of?

• A. Using river rock
• B. Using crushed rock
• C. Inadequate presoaking
• D. Excessive mixing

Answer: (C)

Excessive slump loss during pumping points to inadequate moisture already present in the aggregates. Slump measures how workable the concrete is, and as the mix is pumped through hoses and elbows, water can be drawn out of the paste by dry aggregates and by shear and friction in the lines. If the aggregates are prewetted to their absorption capacity (presoaked), they carry moisture with them and pull less water from the cement paste, so the slump doesn’t drop as much. So the best explanation is that not enough presoaking allows the aggregates to absorb paste water during pumping, causing a greater loss of slump. The other factors—rock type or excessive mixing—aren’t the primary cause of slump loss in pumping, though aggregate properties can influence water demand; the moisture state of the aggregates is the key.

Excessive slump loss during pumping points to inadequate moisture already present in the aggregates. Slump measures how workable the concrete is, and as the mix is pumped through hoses and elbows, water can be drawn out of the paste by dry aggregates and by shear and friction in the lines. If the aggregates are prewetted to their absorption capacity (presoaked), they carry moisture with them and pull less water from the cement paste, so the slump doesn’t drop as much. So the best explanation is that not enough presoaking allows the aggregates to absorb paste water during pumping, causing a greater loss of slump. The other factors—rock type or excessive mixing—aren’t the primary cause of slump loss in pumping, though aggregate properties can influence water demand; the moisture state of the aggregates is the key.