7 manifestations of concrete compatibility

Admixtures can improve the working performance of fresh concrete, improve the construction environment, improve the mechanical properties and durability of hardened concrete, and at the same time save cement, reduce costs, and speed up construction. Therefore, concrete admixtures are widely used in various concrete projects. However, concrete raw materials are different across our country, and the production process and scale of the raw materials are quite different. This not only leads to the diversity and complexity of concrete raw materials, but also the great difference in quality. In the application of high-performance concrete, high-strength concrete, and pumped concrete, poor compatibility between concrete admixtures and concrete raw materials often occurs. Especially in terms of compatibility between cement and admixtures, under the same ratio, concrete admixtures of the same type and dosage often have greatly different application effects due to different cement types. The same kind of concrete admixture has a better effect in the application of a certain type of cement, but there is a big difference in the application of another type of cement, or even the opposite effect, and serious quality accidents may occur. For example, concrete admixtures mixed with “glycerin” or “sugar calcium” or “wood calcium” have ideal application effects in some cements, but the opposite effect may occur in some cements. When concrete has good compatibility with admixtures: the ratio of initial slump to flow expansion of concrete is around 0.4, and the slump loss is 20 to 30mm in one hour. The symptoms of poor compatibility of admixtures in concrete are:

(1) Cannot come out of the machine: dry, bean dregs-like, dry and hard concrete, and the concrete after the machine has no fluidity;

(2 ) Loss at extrusion: initial viscosity, flow disappears within 5 minutes;

(3) Cannot be maintained: initial condition is excellent, flow disappears within 15 minutes;

(4) Collapse loss is fast : Severe bleeding, high water reduction, but the loss is still fast, flow loss in 1 hour;

(5) Poor concrete cohesion state: high fluidity concrete exposed stone, segregation, bleeding, and sticky bottom. tank; low-fluidity concrete slurry is non-stick, divergent, astringent, and has poor wrapping properties;

(6) Sensitive: Use particularly adaptable cement and washed sand and gravel, and when the dosage of admixtures is low, The fluidity of concrete is lost too quickly; bleeding occurs after increasing the dosage;

(7) The fluidity increases with time: the concrete is just right when it comes out of the machine, but the fluidity increases when it arrives at the site, and there is local segregation after molding , bleeding, sand line phenomena, cracks and appearance problems.

Factors affecting the adaptability of admixtures

There are many factors that affect the adaptability of admixtures. From a broad perspective, they can be divided into factors of the admixture itself, glue materials and aggregates. Impact.

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