Types of concrete

Some common and main sorts of concrete are:

1. traditional concrete

2. High Strength Concrete

3. High Performance Concrete

4. Air Entrained Concrete

5. light-weight Weight Concrete

6. Self Compacting Concrete

7. Shotcrete

8. permeable Concrete

9. Roller Compacted Concrete

Normal Concrete:

·        The concrete in which common ingredients i.e. aggregate, water, cement are used is known as normal concrete. It is also called normal weight concrete or normal strength concrete.

·        It has a setting time of 30 - 90 minutes depending upon moisture in atmosphere, fineness of cement etc.

·        The development of the strength starts after 7 days the common strength values is 10 MPa (1450 psi) to 40 MPa (5800 psi). At about 28 days 75 - 80% of the total strength is attained.

·        Almost at 90 days 95% of the strength is achieved.

Properties of Normal Concrete

·        Its slump varies from 1 - 4 inches.

·        Density ranges from 140 pcf to 175 pcf.

·        It is strong in compression and weak in tension.

·        Air content 1 - 2 %.

·        Normal concrete is not durable against severe conditions e.g. freezing and thawing.

2. High strength concrete

Compressive strength of high strength concrete combine is typically bigger than vi,000 pounds per area unit.

High strength concrete is formed by lowering the water cement (W/C) quantitative relation to zero.35 or lower.

Often silicon oxide fume is added to forestall the formation of free slaked lime crystals within the cement, which could cut back the strength at the cement mixture bond.

Low w/c ratios and therefore the use of silicon oxide fume create concrete mixes considerably less possible, that is especially doubtless to be a drag in high-strength concrete applications wherever dense rebar cages area unit doubtless to be used. To atone for the reduced workability within the high strength concrete combine, super plasticizers area unit unremarkably added to high-strength mixtures.

Aggregate should be hand-picked rigorously for prime strength mixes, as weaker mixtures might not be robust enough to resist the masses obligatory on the concrete and cause failure to start out within the aggregate.

3.High Performance Concrete

This combine has the subsequent main properties:

High strength.

High workability.

High sturdiness.

Ease of placement.

Compaction while not segregation.

Early age strength.

Long-term mechanical properties.

Permeability.

Density.

Heat of association.

Toughness.

Volume stability.

Long life in severe environments.

Preparation

High strength concrete combine may be ready with careful choice of ingredients and improvement of combine style.

High workability is earned by super plasticizers, they lower the water cement quantitative relation to zero.25 that is that the quantity needed just for association method.

High sturdiness is attributed to ash and silicon oxide fume that modify the e geology of the cement; it enhances the compatibility of ingredients in concrete mass and reduces the CH quantity. ash conjointly causes bearing result increasing workability.

The admixture area unit 20-25% ash of partial replacement of cement and rest seventieth is standard cement.

As it isn't typically sturdy against chilling and thawing thus air entrained agents can even be used.

Properties of high performance concrete combine
Strength of high performance concrete ranges from ten thousand psi - 15000 psi

Water cement quantitative relation may be reduced to zero.25

4. Air Entrained Concrete

One of the best achievements in field of concrete technology is development of air entrained concrete. it's used wherever the concrete is at risk of phase change and thawing action.

It is used wherever the concrete is at risk of phase change and thawing action. it's ready by adding the air entraining admixture.

The air entrainment in concrete will the subsequent functions:.

It lowers the physical phenomenon of water and therefore bubbles area unit created.

Secondly the air entraining agents prevents coalescing i.e. the combining of bubbles. The diameter of those bubbles ranges kind ten micrometer to a thousand micrometer and in entrapped air the diameter of bubble is larger than 1mm.

Air entraining agents OR air entrained admixtures area unit used for the aim of constructing entrained air in concrete.

5. FREEZING AND THAWING:

There ar 2 phenomenon’s relating to the state change and thawing action on concrete.

when water within concrete mass freezes it expands 9-10% thanks to this increase within the size it exerts pressure on its encompassing and so making a tensile force thanks to that small cracks seem within the concrete. Thanks to state change these small cracks change into fissures which end in disruption of concrete.

When the air entrained agents ar gift, additional quantity of air is there as water expands these bubble offer them skinny house and therefore the effort of pressure is prevented.

Second is of diffusion pressure: in an exceedingly concrete structure there ar 2 elements, frozen and melted. Because the water content is higher within the frozen half, the pressure level is developed and water tends to flow towards the low tide concentration half. If capillaries aren't accessible, the water develops cracks.

Normal concrete cannot sustain 3-4 cycles of state change and thawing wherever because the AEA concrete will sustain one hundred cycles of it.

DRAW BACKS of Air Entrained Concrete:
It has low strength as compare to traditional concrete.

 6. LIGHT WEIGHT CONCRETE

The concrete that has well lower mass per unit volume then the concrete manufactured from normal ingredients is termed light-weight concrete. The aggregates used area unit lighter in weight.

Density of sunshine weight concrete is 240 kg/m³ (15pcf) -1850 kg/m³ (115 pcf).

Strength of sunshine weight concrete blocks varies from seven MPa (1000 psi) - forty MPa (5800 psi).

Some times Air Entrained Admixtures also are intercalary to that giving resistance to state change and thawing along side strength.

Uses of sunshine weight concrete:
Used wherever additional load isn't applied e.g. parapet wall, road lining etc. or to scale back load.

7.SELF COMPACTING CONCRETE

The concrete wherever no vibration is needed. The concrete is compacted because of its own weight. It’s conjointly referred to as self consolidated concrete or flowing concrete. It is conjointly classified as high performance concrete because the ingredients area unit a similar, however during this style of concrete workability is enlarged. This self-consolidating concrete is characterized by:

Extreme liquidity as measured by flow, usually between 650-750 millimeter on a flow table, instead of slump (height).

No want for vibrators to compact the concrete.

Placement being easier.

No bleed water, or mixture segregation.

Uses and Applications of Self Compacting Concrete:

It is employed in location unaccessible for vibrations. e.g. underground structure, deep wells or deep down of deep ocean.


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