Civil Engineering Materials

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Civil Engineering Materials

• Department of Civil, Structural and Environmental
  Engineering
• Trinity College Dublin

Dr. Roger P. West (TCD) And Mr. Peter Flynn (Arup)
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Schedule

• Lectures
• Weeks 1-3(Wed 3-5) Timber, aluminium, glass and
  pre-cast
• Weeks 4-9(Mon 10-11, Fri 3-4) Concrete,
  reinforced concrete and pre-stressed concrete
• Tutorials
• Alternate weeks, weeks 4-9, Thursday 5-6pm,
  commencing Groups 1-20 in week 4 of term, in Joly
  Theatre
• Concrete Laboratory
• Each laboratory group on either Monday or
  Thursday, for one week only, as per timetable

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• Section A Concrete

• A1 Basic Materials

• A2 Fresh Concrete Properties

• A3 Hardened Concrete Properties

• A4 Concrete Mix Design

• A5 Reinforced Concrete

• A6 Pre-stressed Concrete

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• What is Concrete?

• Concrete is the most widely used construction
  material in the world

• Concrete is a construction material composed of
  crushed rock or gravel and sand bound together
  with a hardened paste of cement and water.

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• Concrete History

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• Concrete History

• Aquaducts

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• Concrete History

• Colleseum

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• Concrete History

• Pantheon

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• Concrete History

• Eddystone Lighthouse John Smeaton (1756)

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• Concrete History

• Joseph Aspdin Patent (1824)

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• Concrete History

• Reinforced Concrete Flower Pot (Joseph Monier
  1867)

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• Concrete History

• Weavers Mill Swansea (1898)

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• Concrete History

• Freysinnet

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• Concrete History

• Hoover Dam

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• Concrete History

• Astrodome

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• Concrete History

• Toronto Tower

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• Section A.1 Basic Materials

1. Cement
2. Water
3. Aggregates
4. Admixtures
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• Section A.1 Basic Materials

1. Cement

• Ordinary Portland Cement (OPC)

• Rapid Hardening Portland Cement (RHPC)

• Sulphate Resistant Portland Cement (SRPC)

• White Portland Cement (WPC)

Specialised Portland Cements

• Masonry Portland Cement

• Low Heat Portland Cement

• Hydrophobic Portland Cement

• Oil-well Portland Cement

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Alternative Cement Replacement Materials

• Blastfurnace Slag Cement (GGBS)
• Pulverised-fuel Ash Cement (PFA)
• Metakaolin
• Rice Husk Ash
• Silica Fume
• Cements in Europe are classed as CEM1 (OPC or
  RHPC), CEM2-4 (OPC with limestone, PFA or GGBS)
  in varying proportions pre-blended

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• Section A.1 Basic Materials

1. Cement

• Chemistry of OPC

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• Section A.1 Basic Materials

1. Cement

• Manufacture

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• Section A.1 Basic Materials

1. Cement Manufacture
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• Section A.1 Basic Materials

1. Cement

• Sulphate Resistant Portland Cement

• Low triacalcium aluminate content (C3A)

• Achieved by adding Iron oxide to decrease
  aluminate proportions

• Resistant to sulphates but not resistant to
  strong acids

• Reduced early heat

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• Section A.1 Basic Materials

1. Cement

• Pulverised-fuel ash cements (latent hydraulic
  binder)

• From burning pulverised coal in power station
  furnaces

• Reacts with calcium hydroxide (lime) to from
  cementitious material

• Resistant to sulphates but not resistant to
  strong acids

• Reduced early heat of hydration

• Reduced early age strength

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• Section A.1 Basic Materials

1. Cement

• Blastfurnace Slag Cements (latent hydraulic
  binder)

• By-product of iron smelting, quenched slag forms
  granuels

• Generally blended with OPC up to 35

• Reduced early age strength

• Reduced early heat of hydration

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• Section A.1 Basic Materials

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• Section A.1 Basic Materials

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• Section A.1 Basic Materials

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• Section A.1 Basic Materials

1. Cement

• Delivery Storage

• Usually packaged in 25kg bags or transported in
  bulk tankers

• Retail price 5

• Warehouse set

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• Section A.1 Basic Materials

2. Water

• Should be free from impurities

• Unsuitable if it contains - sugars
• - sulphates
• - chlorides

• Sea water must not be used for reinforced
  concrete

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• Section A.1 Basic Materials

Hydration

• Setting and hardening results from a chemical
  reaction between the cement and the water, not
  from a drying process.

• The reaction is exothermic and is irreversible.
  The heat produced is known as the Heat of
  Hydration C3A and C3S are the compounds
  primarily responsible.

• The paste is usually workable up to two hours
  before it begins to harden

• Strength gain is initially rapid becoming
  progressively less rapid

• Strength gain continues indefinitely provided
  moisture is present.Curing

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• Section A.2 Fresh Concrete Properties

2. Cement hydration
Cement H2O Calcium Silicate Hydrate (C-S-H)
Ca (OH)2 H2O
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• Section A.2 Fresh Concrete Properties

2. Cement hydration and heat generation
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• Section A.1 Basic Materials

2. Cement paste strength gain
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• Section A.1 Basic Materials

3. Aggregates

• Gravels, crushed rock and sands that are mixed
  with cement and water to produce concrete.

• Coarse aggregates are those that do not pass
  through a 5mm sieve.

• Fine aggregates are those that pass through a 5mm
  sieve.

• Generally make from 50 to 80 of the concrete
  mix.

• Used to reduce cost and modify and imporve
  properties like strength and drying shrinkage.

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• Section A.1 Basic Materials

3. Aggregates

• Quality Requirements

• Durability - Hard
• - Adequate Strength
• - No deletrious material

• Cleanliness - free from chemical impurities
• - free from organic material
• - free from dust
• - excessive washing is not the answer
• - avoid silica acid aggregates.

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• Section A.1 Basic Materials

3. Aggregates

• Aggregate Types

• Normal density - Most gravels and crushed rock
• - Divided into coarse and fine

• Lightweight - Weak porous solids
• - Good thermal properties

• High Density - radioactive screening

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• Section A.1 Basic Materials

3. Aggregates

• Sieve Analysis

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• Section A.1 Basic Materials

4. Admixtures

• Additives to the concrete mix to improve certain
  properties

• Must be used with care as excessive amounts can
  have adverse effects on the concrete

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• Section A.1 Basic Materials

4. Admixtures

• Accelerators

• Increases the rate of strength gain at an early
  age

• Most common is calcium chloride (CaCl) but may
  corrode steel

• Most common is calcium chloride (CaCl) but may
  corrode steel

• Does not increase final strength

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• Section A.1 Basic Materials

4. Admixtures

• Water Reducing Admixtures (Plasticisers)

• Reduces the amount of water required for a given
  workability

• Most common is calcium ligno-sulphate

• Reduces the risk of evaporation cracks

• Air Entraining Admixtures

• Generates evenly dispersed air bubbles in the mix

• Improves durability against frost and marine
  environments

• Volume or air entrainment should not exceed 13
  of cement paste

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• Section A.1 Basic Materials

4. Admixtures

• Retarding Agents

• Reduces the rate of evolution of heat

• Necessary for very large concrete pours

• Water-repelling admixtures

• Can improve impermeability of concrete in
  basements and water retaining structures

• No substitute for sound concrete

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• Section A.1 Basic Materials

4. Admixtures
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Section A.1 Basic Materials

• Admixtures
• Foaming Agents
• Produces highly flowing light concrete
• Superplasticiser
• Produces flowing normal concrete with high
  strength
• Self-compacting
• Allows highly flowing cohesive mix with no
  need for vibration. It can also be
  self-levelling.