The Causes and Solutions to the Problem of Slump Loss and Slump Unstable in Pumped Concrete

1. Reasons

(1) The admixture of concrete admixture with cement is not sufficient to cause a rapid loss of concrete slump.

(2) Inadequate mixing of concrete admixtures, delaying the effect of plasticization is not ideal.

(3) When the weather is hot, some admixtures will fail at high temperatures; moisture will quickly evaporate; foam overflow will cause rapid loss of fresh concrete.

(4) The initial concrete slump is too small and the unit water consumption is too small.

(5) The coordination with the mixing station is not good, so that the oil tank press and traffic jam are too long, resulting in excessive loss of concrete slump.

(6) The measurement error of the concrete mixing weighing system is large and unstable.

(7) Change in moisture content of coarse aggregates and fine aggregates.

(8) Cement mixing warehouse storage, mixed use.

2. Solution

(1) Adjust the concrete admixture formulation to suit the cement. Prior to construction, ensure concrete admixtures and cement suitability tests.

(2) Adjust the mixing ratio of the crucible, increase or decrease the sand rate and water consumption, and adjust the initial slump of concrete to 200 mm or more.

(3) Add an appropriate amount of fly ash to replace part of the cement.

(4) Appropriately increase the amount of concrete admixture, and adjust the delay components in the mixture (especially when the temperature is much higher than normal temperature).

(5) To prevent the water from evaporating too quickly, the air bubbles overflow too quickly.

(6) Use slag cement or pozzolan cement.

(7) Improve the water retention and cooling device of the concrete transporter.

(8) The accuracy of the metering equipment shall comply with relevant regulations, and shall have an effective certificate issued by the statutory measurement department, strengthen self-inspection, and ensure accurate measurement.

(9) Strengthen the measurement of the moisture content of aggregates, and adjust the mixing ratio in time when changes occur.

(10) Storage cement should be stored and used according to manufacturer, model and label.

3. Summarize experience

Concrete slump loss issues with pumped concrete, especially pumped concrete and underwater cast pile foundations. Through learning and experimentation, we have concluded a set of solutions to solve problems in light of actual conditions. Such as communication additive manufacturers to improve and adjust the flame retardant composition in the mixture; adjust the concrete construction time, try not to work under high temperature conditions; in the case of poor road conditions, the use of secondary feeding of the mixture; The thorny problem of slump loss in construction of large mixed fly ash concrete mixes is greatly alleviated. No matter what the reason, the slump becomes smaller and cannot be pumped or the slump of the construction requirements cannot be met. We can use the admixture to adjust to achieve the required slump, and eliminate the possibility of adding water to increase the slump. Habits fundamentally determine the quality of concrete!

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