• HISTORY OF CONCRETE

• INTRODUCTION TO CONCRETE

• TYPES OF CONCRETE

• HIGH STRENGHT CONCRETE

• GUIDLINES FOR THE SELECTION OF MATERIALS

• DIFFERENCE B/W NSC AND HSC

• APPLICATION OF HSC

HISTORY OF CONCRETE:

• The word concrete comes from the Latin word "concretus" Which means compact or condensed.

• German archaeologist Heinrich Schliemann found concrete floors, which were made of lime and pebbles, in the royal palace of Tiryns, Greece, which dates roughly to 1400-1200 BC.

Outer view of the Roman Pantheon Dom

INTRODUCTION TO CONCRETE:

• A building material made from a mixture of broken stone or gravel, sand, cement, and water,which can be poured into moulds and forms a stone-like mass on hardening.

• It is strong in compression and very weak in tension.

TYPES OF CONCRETE:• Normal concrete

• High Strength Concrete

• High Performance Concrete

• Air Entrained Concrete

• Light Weight Concrete

• Self Compacting Concrete

• Shotcrete

HIGH STRENGHT CONCRETE:

• High-strength concrete has a compressive strength greater than 40 MPa.

• High strength concrete is made by lowering the water cement (W/C) ratio to 0.35 or lower.

• Due to low w/c ratio it causes problem of placing ,to overcome from this superplasticizer used.

Materials for High-Strength Concrete: Cement:

•Almost any ASTM portland cement type can be used to

obtain concrete with compresive strength up to 60 MPa.

• In order to obtain higher strength mixtures while maintaining good

workability, it is necessary to study carefully the cement composition

and fineness.

Aggregate:

• In high-strength concrete, the aggregate plays an important role on the strength

of concrete.

• The low-water to cement ratio used in high strength concrete causes densification in both the matrix and interfacial transition

zone, and the aggregate may become the weak link in the development of the mechanical strength

Methods Of Making HSC:

• Use of admixture

• Use of cementitious agg

• Seeding

• High speed slurry mixing

Guidelines for the selection of materials:

• The higher the targeted compressive strength, the smaller the maximum size of coarse aggregate.

• Up to 70 MPacompressive strength can be produced with a good coarse aggregate of a maximum size ranging from 20 to 28 mm. •

• To produce 100 MPacompressive strength aggregate with a maximum size of 10 to 20 mm should be used.

Differences Between NSC and HSC:• In normal strength concrete, the

microcracks form when the compressive stress reaches ~ 40% of the strength. The cracks interconnect when the stress reaches 80-90% of the strength

• The fracture surface in NSC is rough.The fracture develops along the transition zone between the matrix and aggregates. Fewer aggregate particles are broken.

• The fracture surface in HSC is smooth.

APPLICATION OF HSC:

• Use of HSC in column section decreases the column size.

• Use of HSC in column decreases amount of steel required for same column.

• In high rise building, use of HSC increases the floor area for rental purpose.

• In bridges,use of HSC reduces the number of beams supporting the slab.

Example of use of HSC in bridges

Vidya Sagar Setu Bridge,Kolkatta,India

Joingy Bridge,Paris

• In joingy bridge,NSC is replaced by HSC because of which volume of concrete decreases by 30%.

• In vidhya sagar setu bridge,because of use of HSC instead of NSC increases the span between two column and strenght.

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