Introduction of

Concrete

Prepared by: Akshay kumar

What is concrete Concrete is a composite material composed

of aggregate bonded together with a fluid cement which hardens over time.

Ingredients - Coarse aggregates - Fine aggregates - Cement - Water - Admixtures

Concrete chain

• Large aggregates:

–provide density (fill space)–provide strength

• Fine aggregates:– fill small voids between large aggregates– Increases strength of the cement binder

• Cement:– produces a crystalline structure– binds aggregates together

• Water– causes chemical reaction to occur – produces workability

Mixing• A concrete mixer is a device that homogeneously

combines cement, aggregate such as sand or gravel, and water to form concrete.

• Type of mixtures 1. Pan type 2.Drum type - Tilting - Non tilting - Reversing

Pan type concrete mixer

Tilting mixer Truck hoist mixer

History of concrete

• The time period during which concrete was first invented depends on how one interprets the term “concrete.” Ancient materials were crude cements made by crushing and burning gypsum or limestone. Lime also refers to crushed, burned limestone. When sand and water were added to these cements, they became mortar, which was a plaster-like material used to adhere stones to each other. Over thousands of years, these materials were improved upon, combined with other materials and, ultimately, morphed into modern concrete.

• Today’s concrete is made using Portland cement, coarse and fine aggregates of stone and sand, and water. Admixtures are chemicals added to the concrete mix to control its setting properties and are used primarily when placing concrete during environmental extremes, such as high or low temperatures, windy conditions, etc.

Transparent concrete

90-95% normal concrete

Ingredients +

5-10% fibers

Properties of Concrete

Fresh concrete 1. Workability 2. Segregation 3. Bleeding

Hardened Concrete

1. Strength 2. Creep 3. Shrinkage

Workability Effort required to manipulate a concrete mixture with

a minimum of segregation.

• Factors affecting 1. w/c ratio2. Size of aggregates3. Shape of aggregates4. Surface texture of aggregates5. w/c ratio

Test for determination of workability 1. Slump test 2. Compacting factor test 3. Vee Bee test 4. Flow test

Slump Test

SegregationSegregation is when the coarese and fine

aggregate , and cement paste, become seperated .

Segregation may happen when the concrete is mixed , transported, placed or compacted.

Bleeding• Water rising to the surface. • Typical of wet mixes.