CONCRETE

Concrete Construction material Mixture of Portland cement, water, aggregates, and in some cases, admixtures. The cement and water form a paste that hardens and bonds the aggregates together.

Concrete is one of the most commonly used building materials.

Concrete is a composite material made from several readily available constituents (aggregates, sand, cement/lime, water).

Concrete is a versatile material that can easily be mixed to meet a variety of special needs and formed to virtually any shape.

Concrete

Can be placed or molded into virtually any shape and reproduce any surface texture.

The most widely used construction material in the world.

The ready-mix concrete producer has made concrete an appropriate construction material for many applications.

Basic ingredients of concrete

Binding materials: lime, cement. Fine aggregates: sand, surkhi etc Coarse aggregates: crushed stones,

broken bricks, gravel and so on.

Advantages

EconomicalDurableFire resistantEnergy efficientOn-site fabrication

Characteristics/Qualities of Concrete

Concrete’s properties make it the building material of choice for most purposes. The most important features are:

Strength and Durability Versatility Low maintenance Affordability Fire-resistance Thermal mass Locally produced and used Compactness

Strength and Durability

Used in the majority of buildings, bridges, tunnels and dams for its strength

Not weakened by moisture or mould Concrete structures can withstand

natural disasters such as earthquakes and hurricanes Roman buildings over 1,500 years old such as the Coliseum are living examples of the strength and durability of concrete

Versatility (usefulness)

Concrete is used in buildings, bridges, dams, tunnels, sewerage systems pavements, runways and even roads

Low maintenance Concrete, being , compact and non-

porous, does not attract mould or lose its key properties over time

Affordability

Compared to other comparable building materials, concrete is less costly to produce and remains extremely affordable

Fire-resistanceBeing naturally fire-resistant

concrete forms a highly effective barrier to fire spread

Thermal mass

Concrete walls and floors slow the passage of heat moving through, reducing temperature swings

This reduces energy needs from heating or air-conditioning.

Locally produced and used

Very little cement and concrete is traded and transported internationally

This saves significantly on transport.

Compactness(Density)

Concrete must be sufficiently dense Compacted Minimum shrinkage Economical for desired strength Sophisticated appearance

CementWater

Fine Agg.Coarse Agg.admixtures

Main Ingredients of concrete

AGGREGATES Aggregates occupy 60 to

80 percent of the

volume of concrete.

Sand, gravel and crushed stone are the

primary aggregates used.

All aggregates must be essentially free

of silt and/or organic matter.

PROPERTIES OF FRESH CONCRETE

WorkabilityConsistencyBleedingSetting TimeUniformity

WATER

Good water is essential for quality concrete. should be good enough to drink--free

of trash, organic matter and excessive

chemicals and/or minerals. The strength and other properties of

concrete are highly dependent on the

amount of water and the water-cement ratio.

TYPES OF CONCRETE AND ITS USESCLASSIFICATION ACCORDING TO BINDING

MATERIAL:

concrete is classified into two major types.(1)Cement concrete (2) lime concrete.

1-CEMENT CONCRETEThe concrete consisting of cement, sand/fine aggregate and coarse aggregates mixed in a suitable proportions in addition to water is called cement concrete. In this type of concrete cement is used as a binding material, sand as fine aggregates and gravel, crushed stones as coarse aggregates.

USEScement concrete is commonly used in buildings and other important architectural as well as engineering works where strength and durability is of prime importance

2-LIME CONCRETE

The concrete consisting of lime, fine aggregates, and coarse aggregates mixed in a suitable proportions with water is called lime concrete.In this type of concrete hydraulic lime is generally used as a binding material, sand and cinder are used as fine aggregates and broken bricks, gravel can be used as coarse aggregates.

PLACING OF LIME CONCRETE :Placing of concrete shall be completed within three hours of adding water in case of concrete is prepared with hydraulic lime. lime Concrete should be well cured for a period of at least 10 days.

USES:Lime concrete is generally used for the sake of economy in foundation works, under floors, over roof and where cement is not cheaply and easily available in required quantity.

TYPES OF CONCRETE AND ITS USESCLASSIFICATION ACCORDING TO

DESIGN OF CONCRETE

(1)Plain cement concrete.(2) Reinforced cement

concrete(RCC).(3) Pre-stressed cement

concrete(PCC).

PLAIN CEMENT CONCRETE

The cement concrete in which no reinforcement is provided is called plain cement concrete or mass cement concrete.This type of concrete is strong in taking compressive stresses but weak in taking tensile stresses.

USES: Plain cement concrete is commonly used in for foundation work and flooring of buildings.

REINFORCED CEMENT CONCRETE(RCC)

The cement concrete in which

reinforcement is embedded for taking tensile stress is called reinforced cement concrete.In this type of concrete the steel reinforcement is to be used generally in the form of round bars,6mm to 32mm dia. This concrete is equally strong in taking tensile, compressive and shear stresses. USES: RCC is commonly used for construction of slabs, beams, columns, foundation, precast concrete.

REINFORCED CEMENT CONCRETE(RCC)

CURING OF CONCRETE

The process of keeping concrete wet to enable it to attain full strength is known as curing.

The objective of curing is to prevent loss of moisture from concrete due to evaporation or because of any other reasons.

Curing should be done for a period of three weeks but not less then 10 days.

CURING OF CONCRETE

To do curing, any one of the following method can be used.

i. The surface of concrete is coated with a layer of bitumen or similar other waterproofing compound which gets into the pores of concrete and prevent loss of water from concrete.

ii. Concrete surface is covered with waterproof paper or with a layer of wet sand. It could also be covered with gunny bags.

CURING OF CONCRETE

Mixing machine