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AD01CTS AD01CTS ‐‐ADVANCED CONSTRUCTION ADVANCED CONSTRUCTION TECHNOLOGY AND SERVICES TECHNOLOGY AND SERVICES

Alfrendo Satyanaga

Lecture 2 Lecture 2 –– Concrete FrameConcrete Frame

Famous Concrete StructureFamous Concrete Structure

• Pantheon, Rome

• Plain concrete

• Construction was started in 118 AD

• Completed in 128 AD


• Coliseum, Rome

• Plain concrete

• Constructed in 70 AD

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• Three Gorges Dam, Yangtze River, China

• World’s heaviest concrete structureconcrete structure

• 144 billion pounds of concrete


• Trump international hotel and tower, Chicago, USA

• World’s tallestWorld s tallest concrete building

• 98th floor

• Completed in 2009


• Thomas Heatherwick’s learning hub in NTU, Singapore

• 12 staggered towers12 staggered towers

• 1000 concrete panels



• Bishan central condominium, Singapore

• 500 units500 units

• 38th story building

• 12,000 m2

• Part of sky habitat project in Singapore


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• The Interlace, condo residences in Alexandra Road, Singaporeg p

• It will be completed in 2018

• 24th storey building

• 23 blocks, 1040 units

Concrete ApplicationsConcrete Applications

• Residential and commercial buildings

• Bridges, flyovers, culverts

• Dams, tunnels, water tanks

• Swimming poolsSwimming pools

• Roads, runways, pipes

• Foundations, piles, sewers

• Offshore platforms

• Nuclear power stations, radiation shields etc.

• Fire and corrosion protection of steel structures

Concrete FactConcrete Fact

• The most used man‐made material

• The 2nd most used material

• Total value of concrete infrastructure > 17 trillion US dollars

• Annual consumption of concrete in the world

– 18 billion ton/year (as of 2015)

– About 3 tons per person

– More than 10x that of steel

Advantages of Advantages of ConcreteConcrete

• Ease of production from local materials(cost benefit)

• Good compressive strength

• Protection of embedded steel (fireresistance)

• Mouldability to achieve any shape andsize (flexibility of application)

• A durable material in principle

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Advantages of Advantages of ConcreteConcrete

• Require less energy to produce thanother construction materials

• Aesthetic possibilities through the useAesthetic possibilities through the useof color, texture and shape

• A material with tailorable properties

Disadvantages of Disadvantages of ConcreteConcrete

• A brittle material with very low tensilestrength and tensile ductility.

• Low strength‐to‐weight ratio (even incompression)compression)

• Prone to chemical attack

• Undergoes irreversible shrinkage due tomoisture loss

• Creep significantly under an appliedload

What is Concrete?What is Concrete?

• Concrete is made by mixing:

– Cement

– Fine aggregatesgg g

– Coarse aggregates

– Water

Concrete AdmixtureConcrete Admixture

• An additional material, known as admixture, is

sometimes added to modify certain properties of

concrete

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Concrete AdmixtureConcrete Admixture AbsorptionAbsorption

Internal impervious

Pores partially filled

Free moisture

Oven dry mass, WD

Air dry-moisture condition,

Wm

Saturated surface dry-

moisture condition,

WSSD = WD +WP

Moist-moisture condition,

Wm

AbsorptionAbsorption

• Absorption (A) is the moisture content

when the aggregates are in saturated

D

DSSD

W

WWA

surface dry condition (SSD)

Free MoistureFree Moisture

• Free moisture is the moisture content

(M) in excess of the SSD condition

D

Dm

W

WWM

AMmoistureFree

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Aggregates in Concrete Aggregates in Concrete Functions of Aggregates in Concrete Functions of Aggregates in Concrete

• Reduce costs

• Modify properties of concrete

• Reduce dry shrinkage

AdmixturesAdmixtures

• Admixtures are substances that are introduced into a batch of concrete during orof concrete, during or immediately before its mixing, in order to alter or improve the properties of the fresh or hardened concrete or both

Use of AdmixturesUse of Admixtures

• To improve the workability of the fresh concrete

• To reduce water content for a given workability thereby increasing the strengthworkability thereby increasing the strength

• To increase the durability of hardened concrete

• To retard setting time or to increase it

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Use of AdmixturesUse of Admixtures

• To impart colour to concrete

• To maintain volume stability by reducing or offsetting shrinkage during concreting

T i i f i• To increase concrete resistance to freezing and thawing

Reinforced Concrete Reinforced Concrete

• Basically made of two materials: plain concrete and steel bars embedded in concrete.

• The tensile strength of concrete is only about• The tensile strength of concrete is only about 10 % of the compressive strength assumed does not resist any tensile forces.

• Reinforcement is designed to carry the tensile strength.

Reinforce Concrete Reinforce Concrete

• Proper bonding is required to prevent slip of the bars

• Proper concrete mixtures are needed to provide adequate impermeability of theprovide adequate impermeability of the concrete against water intrusion and bar corrosion

StressStress‐‐Strain RelationshipStrain Relationship

• As the load is applied, at first strain increases linearly with stress and the concrete behaves as an elastic material.

• After that the curve is no longer linear and• After that the curve is no longer linear and the concrete behaves more like plastic material.

• In the plastic range, if the load is removed, the deformation would not recover.

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StressStress‐‐Strain Curve for ConcreteStrain Curve for Concrete Concrete StrengthConcrete Strength

• Concrete generally increases its strength with age.

• A typical variation in strength of an adequately cured Portland Cement Conreteadequately cured Portland Cement Conrete as suggested by BS8110 is:

• BS 8110 does not permit the use of strengths greater than the 28‐day value in calculations

Duration 7 days 1 month 2 months 3 months 6 month 1 year

Strength (N/mm2)

20 30 33 35 36 37

Durability of ConcreteDurability of Concrete

The durability of concrete is influenced by:

• The exposure conditions

• The concrete quality

• The cover to the reinforcement

• The width of any cracks

Specification of ConcreteSpecification of Concrete

• Concrete of a given strength is identified by

its “grade”

• For example Grade 25 concrete has aFor example Grade 25 concrete has a

characteristic cube crushing strength of 25

N/mm2 after 25 days of curing.

• For normal dense aggregate reinforced

concrete use grades of 30, 35, 40

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Typical Properties of Structural ConcreteTypical Properties of Structural Concrete

Properties

Compressive strength (MPa) 35

Flexural strength (MPa) 6

Tensile strength (MPa) 3

M d l l ti it (GP ) 28Modulus elasticity (GPa) 28

Tensile strain at failure 0.001

Cofficient of thermal expansion (/oC) 10 x 10‐6

Ultimate shrinkage strain (%) 0.05 – 0.1

Density

Normal weight (kg/m3) 2300

Light weight (kg/m3) 1800

Environmental Impact of ConcreteEnvironmental Impact of Concrete

Enormous raw material and energy consumption

• Global concrete demand > 18 billion tons annually as of 2006

• 1 ton of cement clinker requires 1.7 tons of qnon‐fuel raw materials

• Cement production is 10x more energy intensive than general economy and is account for 2% of global primary energy use (4000‐7500 MJ per tonne of cement)

• Land scarring

Environmental Impact of ConcreteEnvironmental Impact of Concrete

CO2 emission and climate change

• Production of 1 ton of cement clinker generates equal amount of greenhouse gas

C d i f 5 10% f• Cement production accounts for 5‐10% of global CO2 emissions

Surface runoff

Urban heat island

ShrinkageShrinkage

• As concrete hardens there is a reduction in volume.

• This shrinkage is liable to cause cracking of the concreteconcrete.

• It also has the beneficial effect of strengthening the bond between the concrete and the steel reinforcement.

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Thermal ExpansionThermal Expansion

• Day‐to day thermal expansion of concrete can be greater than the movements caused by shrinkage.

• When the tensile stresses caused by shrinkage• When the tensile stresses caused by shrinkage or thermal movement exceed the strength of concrete, cracking will occur.

• To control the crack widths, steel reinforcement must be provided close to the concrete surface.

Workability & ConsistencyWorkability & Consistency

• It is desirable that freshly mixed concrete be relatively easy to transport, place, compact and finish without harmful segregation. A concrete mix satisfying these conditions is said to bemix satisfying these conditions is said to be workable.

• It is determined to a large extent by measuring the “consistency” of the mix. Consistency is the fluidity or degree of wetness of concrete.

Factors Affecting WorkabilityFactors Affecting Workability

• Method and duration of transportation.

• Quantity and characteristics of cementingmaterials.

A di h d f• Aggregate grading, shape and surface texture.

• Quantity and characteristics of chemicaladmixtures.

• Amount of water.

• Amount of entrained air.

• Concrete & ambient air temperature.

BleedingBleeding

• Bleeding is the tendency of water to rise to the surface of freshly placed concrete.

• It is caused by the inability of solid constituents of the mix to hold all of theconstituents of the mix to hold all of the mixing water as they settle down.

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Working Life of Concrete StructureWorking Life of Concrete Structure Concrete Structural FormConcrete Structural Form

• Flat slab

• Ribbed slab

• Waffle slab

• Band beam and slab

• Deep beam and slab

• Hybrid concrete construction

• Precast

• Tunnel form

Flat SlabFlat Slab

• A reinforced concrete slab supported directly by concrete column without the use of beams

Flat SlabFlat Slab

• Common used in construction

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Flat Slab with Drop Panels & Column HeadsFlat Slab with Drop Panels & Column Heads

Use of drop panels:

• Increase shear strength of slab

• Increase negative moment capacity of slab

Stiff th l b d h d d fl ti• Stiffen the slab and hence reduce deflection

Use of column heads:

• Increase shear strength of slab

• Reduce the moment in the slab by reducing the clear or effective span

Benefit of Flat SlabBenefit of Flat Slab

• Flexibility in room layout

• Saving in building height; most economic forms of construction

• Shorter construction time• Shorter construction time

• Ease of installation of M & E services

• Prefabricated welded mesh

• Buildable score

• Can incorporate all edge protection and provide robust working platform (health & safety)

Waffle SlabWaffle Slab

• A type of slab that has two‐directional reinforcement on the outside of the material, giving it the shape of the pockets on a waffle.

Ribbed SlabRibbed Slab

• A pre‐stressed concrete flat half slab with concrete up strands (rib) that are purposely designed to provide the necessary stiffness to the slab for handling

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Construction with Waffle SlabConstruction with Waffle Slab

LodytelLodytelCommunication Communication

Development Centre, Development Centre, SpainSpain

It was the first building to use the Holedeck pods for waffle sytem.

ChattrapatiChattrapati ShivajiShivajiTerminal,IndiaTerminal,India

It is recognized for its innovative column design which also

consists waffle design.

Metropol Metropol Parasol,ItalyParasol,Italy

It is the world’s largest structure which is made up of waffle

system.

Advantages of Ribbed and Waffle SlabAdvantages of Ribbed and Waffle Slab

• Flexible

• Relatively light, therefore less foundation costs and longer spans are economic

• Speed of construction

• Fairly slim floor depths

• Robustness

• Excellent vibration control

• Thermal mass

• Good for services integration

• Durable finishes

• Fire resistance

Disadvantages of Ribbed and Waffle SlabDisadvantages of Ribbed and Waffle Slab

• Construction requires strict supervision and skilled labour.

• The casting forms or moulds required for pre‐cast units are very costly and hence only economical when large scale production of similar units are desired.

• Headroom is reduced , hence increased storey height.

• Due to waffle ceiling , it creates problem in lighting facilities and hanging pipes or ducts.

Ribbed and Waffle SlabRibbed and Waffle Slab

• Commonly used as both ceiling and floor slab. They are used in the areas which has huge spans.

• It is often used for industrial, commercial buildings, airports, parking garages, bridges, residences and th t t i i t t bilitother structures requiring extra stability.

• The main purpose of employing this technology is for its strong foundation characteristics of crack and sagging resistance. Waffle slab also holds a greater amount of load compared with conventional concrete slabs.

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Construction TechniqueConstruction Technique

1. 2. 3.

Arranging the Framework

Fixing the Connectors

Fixing the Framework

4.Providing a horizontal

connector

5.Placing the

Pods

Construction TechniqueConstruction Technique

6. 7. 8.6.Fixing pods to the connectors

7.Removing framework

8.Removing connectors

9.Removing pods

10.Providing stacking

Band Beam and SlabBand Beam and Slab

• Beam and slab construction involves the use of one or two way spanning slabs onto bems spanning in one or two directions

• Band beams are shallow, wide beams thatBand beams are shallow, wide beams that minimise the overall structural depth.

Deep Beam and SlabDeep Beam and Slab

• Deep beam provide a stiff floor capable of long spans, and able to resist lateral loads.

• To limit the formation of flexural cracks along the sidesthe sides

• Beam can be designed as T or L beams using the slab as a flange

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Advantages & Disadvantages of Beam and Advantages & Disadvantages of Beam and Slab ConstructionSlab Construction

Advantages:

• Traditional effective solution.

• Long spans.

• Fast lead time as formwork can be made on siteFast lead time as formwork can be made on site.

Disadvantages:

• Penetrations through beams for large ducts difficult to handle.

• Slow construction.

• Greater floor‐to‐floor height.

PosPos‐‐Tensioned SlabTensioned Slab

Wedge action producing a frictional grip on the wires. Direct bearing from rivet or bolt heads formed at the end of the wiresat the end of the wires. Looping the wires around the concrete.

PosPos‐‐Tensioned SlabTensioned Slab UnbondedUnbonded TendonTendon

• Unbonded tendons are protected by a layer of grease inside a plastic sheath.

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UnbondedUnbonded TendonTendon

• Single strand coated with corrosion inhibiting grease and encased in polyethylene sheathing

• PT force is transferred to the concrete by the anchors provided at the ends

StrandStrand

• Strand is made from seven cold drawn high carbon steel wires.

• Seven individuals wires, with six wires helically wound to a long y gpitch around a centre wire.

• All strands should be grade 1860 Mpa

• Strand is mostly available in two nominal size 12.7mm&15.7mm diameter

Unbonded Tendon Unbonded Tendon

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Bonded TendonBonded Tendon

• Bond is achieved throughout the length of the tendon by a cementitious matrix called grout

• Post‐tension force along the tendon is a function of the deformation of the concrete

Advantages of Bonded TendonAdvantages of Bonded Tendon

• Higher flexural capacity.• Good flexural crack distribution.• Good corrosion protection.• Flexibility for later cutting of penetrationsFlexibility for later cutting of penetrations.• Easier demolition.

Bonded Tendon Advantages of PostAdvantages of Post‐‐Tension SlabTension Slab

Longer span Overall structural cost Reduced floor to floor height. Deflection &cracks controlDeflection &cracks control Waterproof slabs Early formwork stripping Materials handling Fast construction

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Cost Saving of PostCost Saving of Post‐‐Tension SlabTension Slab Disadvantages of PostDisadvantages of Post‐‐Tension SlabTension Slab

Since there are a number of tendons and wires spread inside the post tension slab, it can result in corrosion.

Complexity of work.

Poor workmanship can lead to accidents.

Application of PostApplication of Post‐‐Tension SlabTension Slab

It used to fabricate large members, such as long –span bridge decks of the box – girder type by prestressing together a number of smaller precast unitsprecast units The chief merit of post –tensioning is that it allows the use of curved and stopped‐off cables Post‐tensioning is variably used for strengthening concrete dams, circular prestressing of large concrete tanks & biological shields of nuclear reactors.

Application of PostApplication of Post‐‐Tension SlabTension Slab

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Application of PostApplication of Post‐‐Tension SlabTension Slab Hybrid Concrete ConstructionHybrid Concrete Construction

A method of construction which integrates precast concrete and cast in‐situ concrete to make best advantage of their different i h t liti Th d dinherent qualities. The accuracy, speed and high‐quality finish of precast components can be combined with the economy and flexibility of cast in‐situ concrete

Hybrid Concrete ConstructionHybrid Concrete Construction

Hybrid concrete construction can incorporate all the benefits of precasting, (e.g. form, finish, colour, speed, accuracy,

t i hi h lit dprestressing, high‐quality, assured covers and dense and properly cured covercrete) with all the benefits of in‐situ construction (e.g. economy, flexibility, moulability, continuity and robustness).

Hybrid Concrete ConstructionHybrid Concrete Construction

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Tunnel FormTunnel Form

A formwork system that allows the contractor to cast walls and slabs in a ll l t t fcellular structure form

The end walls and facades are easily completed with thermally insulated units that can be clad as required.

Tunnel FormTunnel Form

Tunnels can be between 8 – 11 m long and 2.4 – 6.8 m width.

Advantages of Tunnel FormAdvantages of Tunnel Form

Fast and economic construction. Example: earthquake recovery housing

project in Turkey 40,000 units completed in 5 months.

Advantages of Tunnel FormAdvantages of Tunnel Form

Easy to use Smooth concrete surface Doors, windows, electrical pipes ready in

place Wide range of building types No height limitations

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Innovations in ConcreteInnovations in Concrete

Ultra‐high performance concrete

Flowing concrete

Self compacting concreteSelf compacting concrete

Fibre reinforced concrete

Nano concrete

UltraUltra‐‐high Performance Concretehigh Performance Concrete

High strength, ductile material formulated

by combining portland cement, silica fume,

quartz flour fine silica sand high‐rangequartz flour, fine silica sand, high range

water reducer, water and steel or organic

fibers.

UltraUltra‐‐high performance concretehigh performance concrete Flowing ConcreteFlowing Concrete

Economical ready mix concrete that allow

maximum flowability without sacrificing

strength by adding water at the jobsitestrength by adding water at the jobsite.

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Self Compacting ConcreteSelf Compacting Concrete

Flowing concrete mixture that is able to

consolidate under its own weight.

It is suitable for difficult conditions and inIt is suitable for difficult conditions and in

sections with congested reinforcement.

It can minimize hearing‐related damages on

the worksite that are induced by vibration of

concrete.

Self Compacting ConcreteSelf Compacting Concrete

FibreFibre‐‐Reinforced ConcreteReinforced Concrete

Concrete containing fibrous material which

increases its structural integrity. It contains

short discrete fibres that are uniformlyshort discrete fibres that are uniformly

distributed and randomly oriented. Fibers

include steel fibers, glass fibers, synthetic

fiber and natural fibers – each of which lend

varying properties to the concrete.

FibreFibre‐‐Reinforced ConcreteReinforced Concrete

Welded wire mesh fiber reinforced

concrete

Glass fiberreinforced concrete

Steel fiberreinforced concrete

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NanoNano ConcreteConcrete

A concrete made with portland cement particles that are less than 500nm as a cementing agent.

Currently cement particle sizes range from a f i ffew nano‐meters to a maximum of about100 micro meters.

Benefits of Benefits of NanoNano ConcreteConcrete

Lower cost per building site.

Concrete with high initial and final

compressive and tensile strengthscompressive and tensile strengths.

Concrete with good workability.

Tutorial QuestionsTutorial Questions

1. Concrete has been used as construction materials

from small to major projects in the world. Define the

composition of concrete. What is its different from

concrete admixture? State the advantages and

disadvantages of concrete as construction materials.


2. A sample of sand has the following properties:

SSD mass = 1533.74 g

Moist mass = 625.2 gg

Dry mass = 589.9 g

Determine: (a) total moisture content, (b) absorption

rate, (c) free moisture content

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3. Reinforced concrete is used as beam, column and slab

in construction.What is reinforced concrete and

what is the purpose to use this material? Describe

three stress‐strain curve of concrete material. What

are factors affecting the durability of concrete?


4. Concrete is commonly used in slab construction.

Describe 3 different types of concrete slabs including

the advantages, disadvantages and the usage of each

slab type. Define the bleeding in concrete

construction.


5. The floor of the boat on top of the Marina Bay Sand

Hotel is constructed using post‐tension slab. Describe

the advantages and disadvantages of this system.

Explain 2 different types of tendons that are used in

post‐tension slabs


6. The latest trend of construction technology using

concrete are hybrid concrete construction and tunnel

form. Describe briefly how both systems are being

constructed. Explain 3 innovations in concrete

technologies.

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