Concrete segregation is a serious problem for concrete in the curing stage. Unfortunately, many people fail to recognize the dangers posed by segregation. Whether you interested in the construction industry or are simply an amateur that's curious about this substance, if you would like to learn more about concrete segregation, read on. This article will provide a helpful overview of this problem.

What Segregation Means

Segregation, at its simplest, refers to the phenomenon whereby the ingredients that make up concrete become separated as the concrete settles. Most commonly, segregation involves the aggregate or gravel chunks sinking down to the bottom of the concrete, rather than remaining suspended in an even matrix. Once segregation has begun to take place, it is very difficult to reverse. The result is often concrete that is much weaker and more prone to degradation over time.

Causes Of Segregation

Segregation may occur for a variety of different reasons. Perhaps the most common is that the concrete mixture has not been properly proportioned. This usually has to do with too much water being added during the mixing process. As a result, the aggregate settles downward through the excessively diluted concrete. Likewise, the use of poorly graded aggregate—in other words, aggregate that is larger and heavier than it should be—tends to increase the risk of segregation.

Another frequent cause of concrete segregation is excessive pour height. This refers to the distance between the chute leading from the concrete mixer to the area into which the concrete is being poured. The greater the distance between chute and slab location, the greater the velocity of the concrete as it hits the ground. This causes heavier elements to sink deeper into the wet concrete, thus forcing water upward toward the surface.

Effects Of Segregation

Segregated concrete leads to a variety of different problems down the line. For one thing, the strength of the fully cured concrete is much weaker. This increases its susceptibility to cracking, spalling, and other forms of damage. It also leads to different depths of the concrete having different levels of strength. For instance, the upper layers will generally be much weaker, since a large proportion of the aggregate has sunk down to the bottom.

The non-homogenous nature of segregated concrete also increases the likelihood of plastic shrinkage cracks forming during the curing process. Such cracks are the result of the drying concrete pulling apart from itself in places. Normally the aggregate embedded in the concrete helps to keep it from separating, but segregated concrete loses this important structural benefit. 

Share