Concrete causes bleeding and segregation problems and solutions

1、the reason
(1) When the cement fineness is large, it is easy to leak water. The content of C3A in the cement is low and the bleeding is easy. The standard consistency of the cement is small and the volume of water is easily bleeding.
(2) The amount of cement is small and easy to bleeding.
(3) Low-grade cement is more prone to bleeding (with same amount) than high-grade cement concrete.
(4) Concrete of the same grade, high-grade cement concrete is more prone to bleeding than concrete of low-grade cement.
(5) The concrete with large water consumption is prone to bleeding and segregation.
(6) The temperature of the concrete mixture is too high, especially in summer, the temperature is high, the hydration reaction is fast, and the slump loss is large.
(7) Concrete with low strength grade is prone to bleeding.
(8) Concrete with small sand rate is prone to bleeding and segregation.
(9) The continuous particle size of gravel is smaller than that of single gravel.
(10) The water retention, thickening, and poor air-entraining properties of concrete admixtures tend to cause bleeding.
(11) Concrete with excess concrete admixture is prone to bleeding and segregation.
(12) The stirring performance of some models of mixing trucks is not good. After a certain distance of transportation, the concrete mixture will obviously float up when it is discharged.
(13) Concrete mixer trucks contain stagnant water in the mixing drum, and they are not drained before loading or during the transportation process, any water is added to the mixing container.
2、the solution
(1) The fundamental way is to reduce the unit water consumption.
(2) increase the sand rate, select a reasonable sand rate.
(3) In hot summer, take measures to reduce the temperature of the concrete mixture.
(4) Increase the amount of cement or add appropriate amount of Class I and II fly ash.
(5) Continuous grading of gravel with small needle-like content.
(6) Improve the performance of concrete admixtures to make them have better water retention and thickening, or reduce the amount of concrete admixture (only on site). If the admixture volume of the concrete admixture is reduced at the mixing station, concrete may be added. New problems with rapid slump loss.
(7) Before the concrete mixing truck is unloaded, the mixing drum should be rotated at medium and high speed so that the concrete mixture is unloaded evenly.
(8) Strengthen management. Before cleaning the trucks, they must be drained before they are filled. After loading, it is forbidden to add water to the mixing bowl.
3、 sum up experience
Concrete is prone to bleeding and segregation problems. Through learning and experimentation, we have concluded a set of solutions to solve problems in combination with actual conditions. Such as optimizing the mix ratio, strengthening the approach to raw material testing, and strengthening site management. Eliminating the phenomenon of arbitrarily increasing water consumption due to poor site management at the mixing plant.

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