Segregation of concrete is a phenomenon in which the cohesion between the components of the concrete mixture is insufficient to resist the sinking of the coarse aggregate, and the components of the concrete mixture are separated from each other, resulting in uneven internal composition and structure. It usually manifests as the separation of coarse aggregate and mortar from each other, for example, dense particles are deposited at the bottom of the mixture, or coarse aggregate is separated from the mixture as a whole.
but may be caused by improper pouring and vibrating, the maximum particle size of the aggregate is too large, the proportion of coarse aggregate is too high, the content of cementitious material and fine aggregate is low, and the coarse aggregate is smaller than the fine aggregate. The density of the material is too high, or the mixture is too dry or too wet, etc. The tendency to segregation can be reduced by using mineral admixtures or air-entraining agents.
1. The hazards of segregation
1.1 It affects the pumping construction performance of concrete, causes sticky tanks, blocked pipes, affects the construction period, etc., and reduces economic benefits.
1.2 Affects the appearance of concrete results, such as sand patterns, exposed aggregates, and exposed steel bars on the surface of the concrete.
1.3 The strength of concrete has dropped significantly, seriously affecting the load-bearing capacity of the concrete structure, damaging the safety performance of the structure, and in severe cases, causing rework and huge economic losses.
1.4 The uniformity of concrete is poor, resulting in inconsistent shrinkage of various parts of the concrete, and concrete shrinkage cracks are prone to occur. Especially when constructing concrete floor slabs, due to concrete segregation, the surface cement slurry layer thickens, shrinkage increases sharply, and serious cracks occur.
1.5 greatly reduces the durability properties of concrete such as concrete impermeability and frost resistance.
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