Concrete

• One of the very important and widely used material in construction

• The Grade of the concrete is specified by its 28 day’s cube strength (E.g. M20 means the cube strength is 20 N/sq.mm)

• Concrete used on works is specified according to IS 456 (2000).

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•Consists of Portland cement, water, and aggregate ( Fine& Coarse )

•Cement, water and fine aggregate – mortar

-Admixtures added for specific purposes like

– Entrain numerous microscopic air bubbles– Retard the initial set of the concrete– Waterproof the concrete , etc.

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Concrete chainCement supply sand supply Coarse aggregate

supplyWater supply

Transporting, unloading and stacking

Gauging

Mixing Slump test

Cube test

Transporting

Placing

Compaction Curing

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PROPORTIONING CONCRETE MIXTURES• For successful utilization, the mixtures must be properly

proportioned ( Mix design )

Concrete Mix Design-IS 10262

Designed to achieve a defined

• workability

• strength

• durability

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BATCHING AND MIXING OF CONCRETE MATERIALS

• Batching is weighing or volumetrically measuring and introducing into the mixer the ingredients for a batch of concrete

• A batch is the quantity of concrete mixed at one time

More accurate to measure by weight

• As per IS 4925 : 1968 - specification for concrete batching and mixing

Slump test to test workability

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Cube test to test the strength

It is a mold used to shape the concrete and support the

concrete until it attains sufficient strength to carry its

own weight.

Formwork system

Introduction No desirable structure can be built without the use of formworks.

Such is the importance of formwork that it constitutes 30% of Cost 60% of Time Construction Apart from that the quality of concrete finish and soundness of concrete depends very much on the formwork system.

Types of Formwork

Formwork can be divided into two approaches :

Traditional approach

Systematic approach (System formwork)

Traditional formwork system in Progress

Wooden posts (ballies)

A network of wooden beams to support the sheathing

System formwork in Progress

Collapsible type props (CT props)

A network of wooden H-beams to support the sheathing.

Pictures and sketches taken from L&T- DOKA formwork manuals

Column Formwork

Pictures and sketches taken from L&T- DOKA formwork manuals

Wall Formwork

Pictures and sketches taken from L&T- DOKA formwork manuals

Beam Forming Support

Pictures and sketches taken from L&T- DOKA formwork manuals