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2.13 SPECIAL CONCRETES Low Cost

Light Weight

Heavy Weight

Underwater

Ultra High Strength

Ultra Durable Architectural

Low Noise

Reduced environmental impact

Fast setting Placing without formwork

Bulk fill

Self compacting

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Low Cost

Cement replacement with PFA - also helpsdurability and workability.

Cement replacement with GGBS - helpsdurability but may increase bleeding.

Water (and cement) reduction with a water

reducer - helps with durability. Cementitious content reduction with CSF -

do not do it.

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2.13 SPECIAL CONCRETES Low Cost

Light Weight

Heavy Weight

Underwater

Ultra High Strength

Ultra Durable Architectural

Low Noise

Reduced environmental impact

Fast setting Placing without formwork

Bulk fill

Self compacting

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Light Weight

Light weight aggregate - some

strength reduction, good

thermal properties.

Foamed concrete - very low

strength.

No-fines concrete

Fig.2.13.1 Shows routes to

producing light weight

concrete and fig.2.13.2 shows

the achievable densities.Foamed concrete

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Lightweight

aggregates

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Lightweight concrete and mortar

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2.13 SPECIAL CONCRETES Low Cost

Light Weight

Heavy Weight

Underwater

Ultra High Strength

Ultra Durable Architectural

Low Noise

Reduced environmental impact

Fast setting Placing without formwork

Bulk fill

Self compacting

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Heavy weight (for shielding)

Heavy weight aggregate

Steel shot - high cost and segregation.

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2.13 SPECIAL CONCRETES Low Cost

Light Weight

Heavy Weight

Underwater

Ultra High Strength

Ultra Durable Architectural

Low Noise

Reduced environmental impact

Fast setting Placing without formwork

Bulk fill

Self compacting

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Underwater concrete

CSF - OK to use it for this - good cohesive

mix.

Non dispersal admixtures.

Note that any concrete may be placed under

water if precautions are used to avoid

washout.

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2.13 SPECIAL CONCRETES Low Cost

Light Weight

Heavy Weight

Underwater

Ultra High Strength

Ultra Durable Architectural

Low Noise

Reduced environmental impact

Fast setting Placing without formwork

Bulk fill

Self compacting

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Ultra high Strength

Superplasticisers (high range water

reducers)

CSF

In-situ de-watering (for slabs)

Must have strong aggregate

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Ultra high performance concrete

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Advantages of High Strength Concrete (HSC)

High durability (e.g. abrasion and carbonation

resistance) High strength to weight ratio, particularly for

lightweight HSC

High early strength allows faster construction andformwork reuse

Increased elastic modulus and lower creep

Very tall buildings become feasible

Lower column costs for concrete and steel Smaller columns allow for more floor space

Box girder and solid girder bridge spans may beincreased and designs simplified

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Disadvantages of HSC

Increased cost per unit volume

More stringent quality control of materials and constructionneeded

CSF mixes may self-desiccate giving failure at day joints.

Workability difficult to define and often declines rapidly with

time after mixing Timing of concrete delivery and addition of admixtures

becomes critical.

High heat evolution may necessitate use of low heat binders(e.g. PFA) and cooling measures.

Stiffness (modulus) does not increase in proportion to strength.

More than 28 days may be required to reach specified strength

Structural members may exhibit brittle failure.

Use of HSC not covered by codes

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2.13 SPECIAL CONCRETES Low Cost

Light Weight

Heavy Weight

Underwater

Ultra High Strength

Ultra Durable Architectural

Low Noise

Reduced environmental impact

Fast setting

Placing without formwork

Bulk fill

Self compacting

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Ultra durable concrete

Ultra high strength with good curing

Controlled permeability formwork

Coated or stainless rebar

Silanes or siloxanes

(Glass fibre in surface)

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Fragmentation resistance with

glass fibre

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2.13 SPECIAL CONCRETES Low Cost

Light Weight

Heavy Weight

Underwater

Ultra High Strength

Ultra Durable Architectural

Low Noise

Reduced environmental impact

Fast setting

Placing without formwork

Bulk fill

Self compacting

C i h d

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Concrete with good appearance

(Architectural concrete)

Avoid plain surfaces Exposed aggregate: Surface retarded,

Bush hammered,

Worked before final set,

Hand placed aggregate

Board finish

Brush finish

Ribbed finish Imprints etc.

White cement, pigments etc.

Note that a highly textured surface may collect dirtand moss.

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Needs a feature to hide colour change

C t ith d

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Concrete with good appearance

(Architectural concrete)

Avoid plain surfaces Exposed aggregate: Surface retarded,

Bush hammered,

Worked before final set,

Hand placed aggregate

Board finish

Brush finish

Ribbed finish Imprints etc.

White cement, pigments etc.

Note that a highly textured surface may collect dirtand moss.

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Exposed

aggregate finish

C t ith d

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Concrete with good appearance

(Architectural concrete)

Avoid plain surfaces Exposed aggregate: Surface retarded,

Bush hammered,

Worked before final set,

Hand placed aggregate

Board finish

Brush finish

Ribbed finish Imprints etc.

White cement, pigments etc.

Note that a highly textured surface may collect dirtand moss.

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Boardfinish

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Patterned

board finish

C t ith d

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Concrete with good appearance

(Architectural concrete)

Avoid plain surfaces Exposed aggregate: Surface retarded,

Bush hammered,

Worked before final set,

Hand placed aggregate

Board finish

Brush finish

Ribbed finish Imprints etc.

White cement, pigments etc.

Note that a highly textured surface may collect dirtand moss.

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Brush Finish

C t ith d

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Concrete with good appearance

(Architectural concrete)

Avoid plain surfaces Exposed aggregate: Surface retarded,

Bush hammered,

Worked before final set,

Hand placed aggregate

Board finish

Brush finish

Ribbed finish Imprints etc.

White cement, pigments etc.

Note that a highly textured surface may collect dirtand moss.

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Profiled (ribbed) finish

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Profiles to hide day joints

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Deep profiles

on wall

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Ribbed (profiled)finished spoiled by

unevenly appliedmould release oil.

Concrete with good appearance

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Concrete with good appearance

(Architectural concrete)

Avoid plain surfaces Exposed aggregate: Surface retarded,

Bush hammered,

Worked before final set,

Hand placed aggregate

Board finish

Brush finish

Ribbed finish Imprints etc.

White cement, pigments etc.

Note that a highly textured surface may collect dirtand moss.

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Imprintedconcrete

Concrete with good appearance

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Concrete with good appearance

(Architectural concrete)

Avoid plain surfaces Exposed aggregate: Surface retarded,

Bush hammered,

Worked before final set,

Hand placed aggregate

Board finish

Brush finish

Ribbed finish Imprints etc.

White cement, pigments etc.

Note that a highly textured surface may collect dirtand moss.

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Pigmented Concrete

Concrete with good appearance

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Concrete with good appearance

(Architectural concrete)

Avoid plain surfaces Exposed aggregate: Surface retarded,

Bush hammered,

Worked before final set,

Hand placed aggregate

Board finish

Brush finish

Ribbed finish Imprints etc.

White cement, pigments etc.

Note that a highly textured surface may collect dirt

and moss.

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2.13 SPECIAL CONCRETES Low Cost

Light Weight Heavy Weight

Underwater

Ultra High Strength

Ultra Durable Architectural

Low Noise

Reduced environmental impact

Fast setting

Placing without formwork

Bulk fill

Self compacting

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Low noise concrete for roads

Random grooves

Exposed aggregate

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2.13 SPECIAL CONCRETES Low Cost

Light Weight Heavy Weight

Underwater

Ultra High Strength

Ultra Durable Architectural

Low Noise

Reduced environmental impact

Fast setting

Placing without formwork

Bulk fill

Self compacting

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Concrete with reduced environmental impact

Cement replacements such as PFA or GGBS save

850kg of CO2 for every tonne of portland cementsaved

No-fines concrete is also known as "pervious"

concrete and can reduce or eliminate run-off fromroads and prevent flooding and pollution.

A bright white concrete surface with GGBS will

reduce the "heat island" effect of cities in hot

climates.

Magnesia or Alumina Cements to replace calcium

silicate

Placing pervious concrete

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Placing pervious concrete

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2.13 SPECIAL CONCRETES Low Cost

Light Weight Heavy Weight

Underwater

Ultra High Strength

Ultra Durable Architectural

Low Noise

Reduced environmental impact

Fast setting

Placing without formwork

Bulk fill

Self compacting

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Fast Setting Concrete for Precasting

Superplasticisers to reduce the water

content are often as effective as

accelerators. High temperature curing - but this can cause

delayed ettringite formation

Autoclaved concrete (high temperature andpressure) for rapid production but the

hydration products are very different.

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2.13 SPECIAL CONCRETES Low Cost

Light Weight Heavy Weight

Underwater

Ultra High Strength

Ultra Durable Architectural

Low Noise

Reduced environmental impact

Fast setting

Placing without formwork

Bulk fill

Self compacting

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Bulk Fill

Foamed concrete

Controlled Low Strength Material (CLSM)

is a flowable fill

Below about 1MPa it can be re-excavated

with a hydraulic excavator

Can be made without cement

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2.13 SPECIAL CONCRETES Low Cost

Light Weight Heavy Weight

Underwater

Ultra High Strength

Ultra Durable Architectural

Low Noise

Reduced environmental impact

Fast setting

Placing without formwork

Bulk fill

Self compacting

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Self Compacting Concrete

Requires viscosity modifier to prevent

segregation

Reduces labour required

Reduces noise

Reduces risk of white-finger

Costs about 30/m3 more