Slide 1

We all know the strength, stability, and durability of concrete depends upon the degree of compaction. So it is so important that the fresh concrete can be properly compacted easily. It must be easily mixed, transported, placed compacted and finish it.

Slide 2

The useful internal work is the work or energy required to overcome the internal friction b/w the individual particles in the concrete. But in practice additional energy is required to overcome the surface friction between concrete and the formwork or the reinforcement. Also, wasted energy is consumed by vibrating the form and in vibrating the concrete which has already been compacted. “consistency” often used loosely for workability - It is a general term to indicate the degree of fluidity or the degree of mobility. but concretes of the same consistence may vary in workability. A concrete which is considered workable for concrete foundation is not workable for roof construction, or even in roof construction, concrete considered workable when vibrator is used, is not workable when concrete is to be compacted by hand. Similarly a concrete considered workable when used in thick section is not workable when required to be used in thin sections. So the word workability assumes full significance of the type of work, thickness of section, extent of reinforcement and mode of compaction.

Slide 3

Slide 4

Water content is a main factor, since by simply adding water the inter-particle lubrication increases and flow of the concrete increases so workability increases. In sites its common tendency to add water to make the mix loose hence workable. But it is not advisory becoz it will cause segregation, bleeding and directly effect the strength and durability. It can be done if all the other correction methods such as aggregate type and grading fails.. With adding cement along with water so that water cement ratio remains constant.

Slide 5

The higher the aggregate/cement ratio, the leaner is the concrete, Less quantity of paste is available for providing lubrication, hence the mobility of aggregate is restrained. It won’t be that much easy to mix and pour it.

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Slide 7

finer particles require more water to wet their larger specific surface, whilst the irregular shape and rougher texture of an angular aggregate demand more water than, say, a rounded aggregate.the total surface area of rough textured aggregate is more than the surface area of smooth rounded aggregate of same volume.

Slide 8

A well graded aggregate is the one which has least amount of voids in a given volume.

Slide 9

Air – entraining agents reduces internal friction – Since air bubbles act as a sort of ball bearing b/w particles to slide each other so better mobility to particles.the fine glassy pozzolanic materials, offer better lubricating effects for giving better workability.

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