TCD Materials A1 (2007)UNIT I SURVEYING AND CIVIL ENGINEERING MATERIALS Foundations: Types, Bearing capacity – Requirement of good foundations Superstructure: Brick masonry – stone

7/30/2019 TCD Materials A1 (2007)UNIT I SURVEYING AND CIVIL ENGINEERING MATERIALS Foundations: Types, Bearing capacity Requirement of good foundations Superstructure: Brick

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2E8 Materials (Civil Engineering Component)

Civil Engineering Materials

Department of Civil, Structural and

Environmental EngineeringTrinity 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, reinforcedconcrete and pre-stressed concrete

Tutorials:

Alternate weeks, weeks 4-9, Thursday 5-6pm, commencingGroups 1-20 in week 4 of term, in Joly Theatre

Concrete Laboratory:

Each laboratory group on either Monday or Thursday, forone 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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Concrete is a construction material composed ofcrushed rock or gravel and sand bound together witha hardened paste of cement and water.

Concrete is the most widely used construction materialin the world

What is Concrete?


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Concrete History


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Aquaducts

Concrete History


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Colleseum

Concrete History


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Pantheon

Concrete History


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Eddystone LighthouseJohn Smeaton (1756)

Concrete History


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Joseph Aspdin Patent (1824)

Concrete History


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Reinforced Concrete Flower Pot (Joseph Monier 1867)

Concrete History


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Weavers Mill Swansea (1898)

Concrete History


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Freysinnet

Concrete History


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Hoover Dam

Concrete History


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Astrodome

Concrete History


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Toronto Tower

Concrete History


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Section A.1 Basic Materials

1. Cement

2. Water

3. Aggregates

4. Admixtures


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1. Cement

Ordinary Portland Cement (OPC)

Sulphate Resistant Portland Cement (SRPC)

White Portland Cement (WPC)

Rapid Hardening Portland Cement (RHPC)

Masonry Portland Cement

Low Heat Portland Cement

Hydrophobic Portland Cement

Oil-well Portland Cement

Specialised Portland Cements:


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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 varyingproportions pre-blended


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Chemistry of OPC

1. Cement


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1. Cement

Manufacture


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1. Cement Manufacture


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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

1. Cement


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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

1. Cement


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Delivery & Storage

Usually packaged in 25kg bags or transported in bulk tankers

Retail price 5

1. Cement

Warehouse set


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Should be free from impurities

Sea water must not be used for reinforced concrete

2. Water

Unsuitable if it contains - sugars

- sulphates- chlorides


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Setting and hardening results from a chemical reaction between the

cement and the water, not from a drying process.

Hydration

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

harden

The reaction is exothermic and is irreversible. The heat produced is

known as the Heat of Hydration C3A and C3S are the compoundsprimarily responsible.

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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2. Cement paste strength gain


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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.

3. Aggregates


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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.

3. Aggregates


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Aggregate Types

Normal density - Most gravels and crushed rock

- Divided into coarse and fine

Lightweight - Weak porous solids

- Good thermal properties

3. Aggregates

High Density - radioactive screening


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Sieve Analysis

3. Aggregates


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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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4. Admixtures

Accelerators

Increases the rate of strength gain at an early age

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

Does not increase final strength

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


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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

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

Air Entraining Admixtures


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4. Admixtures Retarding Agents

Reduces the rate of evolution of heat

Necessary for very large concrete pours

Can improve impermeability of concrete in basements and

water retaining structures

No substitute for sound concrete

Water-repelling admixtures


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4. Admixtures


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4. Admixtures Foaming Agents

Produces highly flowing light concrete

SuperplasticiserProduces flowing normal concrete with highstrength

Self-compacting

Allows highly flowing cohesive mix with no needfor vibration. It can also be self-levelling.

Documents

TCD Materials A1 (2007)UNIT I SURVEYING AND CIVIL ENGINEERING MATERIALS Foundations: Types, Bearing capacity – Requirement of good foundations Superstructure: Brick masonry – stone