Download - 2.13 Special Concretes
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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