Concrete Construction(Week1&2)

7/29/2019 Concrete Construction(Week1&2)

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QUALITY CONTROL, ASSURANCE ANDMONITORING OF CONCRETE

CONSTRUCTION

ECM 754/752

MASTER OF SCIENCE IN CIVIL

ENGINEERING (CONSTRUCTION)


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DR. HAMIDAH MOHD. SAMANTEL : 03 5543 6432 (OFFICE)

019 236 1274 (H/P)

03 5511 5153 (HOUSE)

FAX : 03 5543 5275

Email : [email protected] OR

[email protected]

OFFICE : LEVEL 17, COMPLEX S & T
mailto:[email protected]:[email protected]


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PROG EDUCATIONAL OBJ. (PEO)

Having the ability to apply the advancedconcepts in design related to specialised fieldin civil engineering.

Having the ability to lead and coordinatemultidisciplinary teams.

Practice with professional ethics.


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COURSE OBJECTIVES (COs)

After taking the course, the student should be able to :

CO1: Acquire and apply the design concretemixes considering design criteria andsuitability factors (-PO1).

CO2: Demonstrate ability to solve the problemrelated concrete material specificationand testing conformance to relevant

standards for concrete (-PO2).


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COURSE OBJECTIVES (COs)(Contd)

CO3: Think critically on monitoring andassessment on concrete structures (-PO1).

CO4: Apply the advanced knowledge of science,engineering and or technology onmaterial specification, testing,monitoring, maintenance and repair ofdeteriorated concrete structures (-PO1).


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PROGRAMME OUTCOMES (POs)

PO1 : Ability to think critically and apply theadvanced knowledge of mathematics,science, engineering and technology.

PO2 : Ability to solve engineering problemsthrough independent research, andeffectively communicate the results multi-disciplinary teams.


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CONCRETE CONSTRUCTION

Concrete Material

Concrete Construction


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This 3 hour lecture will

cover : Introduction to concrete as a construction

material.

Constituent of concrete Hydration of Cement


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Learning outcomes of todays

lectureAfter todays lecture, the student will beable to understand and acquire knowledge

on the constituent of concrete and how thechemical and physical properties of thoseconstituent will affect the quality or

properties of concrete produced(CO2-PO2)

.


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Advantages of concrete

Economic Possess high compressive strength

High corrosive and weathering effectsresistance

Can easily be moulded into any shape or size Has equal coefficient thermal expansion with

steel

Can be sprayed on and filled into fine cracks

Durable and fire resistant Can be pumped and can be laid in the difficult

positions.


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Disadvantages of concrete

Low in tensile strength and cracks easily.

Shrinks on drying and expand onwetting/changes in temperature.

Not entirely impervious to moisture and salt

solutions. Liable to disintegrate by alkali and sulphate

attack.

Lack of ductility.

Undergoes creep resulting reduction of pre-stress in the pre-stressed concrete.


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Constituents of concrete :

Mixture of aggregate and paste

Paste 30% to 40 %

- Portland cement 7% to 15%- Water 14% to 21%

Aggregates 60% to 70%

- Coarse aggregate- Fine aggregate


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Aggregate are :

Cheap fillers

Hard material Provide for volume stability

Reduce volume changes

Provide abrasion resistance


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dry powder of very fine particles

forms a paste when mixed with water

chemical reaction especially hydration paste coats all the aggregates

together

hardens and forms a solid mass.

Cement are :


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Water is need for two

purposes :

chemical reaction with cement

(hydration)

workability


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Portland Cement

can be described as a material with adhesiveand cohesive properties which make itcapable of bonding mineral fragments into acompact hole.

Why Portland resemble the colour and

quality to Portland stone a limestonequarried in Dorset.


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History of cement development

Modern cement commissioned in 1756by John Smeaton understand thechemical properties of lime by burning a

mixture of clay and lime.

James Parker and Joseph Aspdin in

1824patented Portland Cement.

Prototyped by Issac Johnson in 1845.


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Historical development (contd)

Modern cement commissioned in 1756by John Smeaton understand thechemical properties of lime by burning amixture of clay and lime.

James Parker and Joseph Aspdin in1824patented Portland Cement.

Prototyped by Issac Johnson in 1845.


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Main Types of Portland Cement

British Description ASTM Description

Ordinary Portland Type 1

Modified Cement Type II

Rapid Hardening Portland Type III

Low Heat Portland Type IV

Sulphate Resistance

Portland

Type V

Extra Rapid Hardening

Portland

Not in ASTM

Description


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Types of cement

Portland cement Slag cements High alumina, BS 915

Pozzolanic

Main Types

Ordinary, BS 12

Rapid

hardening, BS12

SulphateResistance, BS4027

Others

Extra Rapidhardening

Ultra Rapidhardening

Low Heat, BS 1370

White andcoloured, BS 12

HydrphobicWaterproof andwater repellent

Air entraining

PortlandBlastfurnace,

BS 146Low heatPortlandBlastfurnace,BS 4246

Supersulphated BS4248


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Schematic representation of the formation and

hydration of Portland Cement

O2 Si Ca Al Fe

CaO SiO2 Al2O3 Fe2O3

C3S C2S C3A C4AF

Various types of Portland cement

Calcium-silicate hydrated gel Ca(OH)2

Component Elements

Component Oxide

Cement Compounds

Portland Cements

Hydration Products


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Matured paste withw/c = 0.5 andcapillary cavities20%

Matured paste withw/c = 0.3 and

capillary cavities 7%


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OXIDE COMPOSITION OF CEMENT


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MAIN COMPOUNDS

Name of Compound Oxide Composition Abbreviation

Tricalcium silicate 3CaO.SiO2 C3S

Dicalcium silicate 2CaO.SiO2 C2S

Tricalcium

aluminate

3CaO.Al2O3 C3A

Tetracalcium

aluminoferrite

4CaO.Al2O3.Fe2O3 C4AF


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HYDRATION OF CEMENT

The reactions of which Portland cementbecomes a bonding agent take place in a water-cement paste.

In the presence of water, the silicates andaluminates in cement form products of

hydration which in time produce a firm and hardmass the hydrated cement paste.


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TWO MECHANISMS OF HYDRATION OF

CEMENT

Hydration

Hydrolysis


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DEVELOPMENT OF STRENGTH OF

COMPOUNDS


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HEAT OF LIBERATION


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Contribution of the compound to

the strength development and

heat hydrationC3S Contributes to early and later strengthdevelopment. It contributes to heat

hydration.

C2S Contributes to later strength but does not

contribute to heat of hydration.

C3A Does not contribute to early and later

strength but contribute to heat hydration.C4AF Does not contribute to early and later

strength and does not contribute to heat

hydration.


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Aggregates

describe the gravels, crushed stones andother materials which are mixed with cementand water to make concrete.

form about 75% of the volume of concrete therefore the selection of suitable aggregate is

important.


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Standards related to aggregate

BS MS Description

812 30 : 1995 Testing aggregates

882 : 1992 29 : 1995 Spec. for aggregates from

natural sources for concrete

3797 :

1990

Spec. for lightweight

aggregates for masonry units

and structural concrete

410 : 1986 Spec. for test sieve


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Natural

Aggregates

Artificial

Aggregates

Artificial

Aggregates

Natural

Aggregates

Crushed rock Sand and Gravel

Heavy Aggregate Normal Aggregates

Types of Aggregate

LightweightAggregates

Classification of Aggregate


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Normal Density Aggregate

Aggregate having a specific gravitybetween about 2.5 and 3.0 and a bulkdensity in the range 1, 450 to 1,750 kg/m3.

Can coarse or fine aggregate.


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Normal density aggregate can

be classified as :

Coarse aggregate Fine aggregate


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Coarse aggregate

are materials retained on 5 mm BS410 test sieve.

can be classified into threecategories :

- uncrushed- crushed


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Fine Aggregate

is a material which passed through a 5 mm BS410 test sieve. Sand is generally considered to

have a lower size limit of about 0.07 mm,material between 0.06 mm and 0.002 mm isclassified as silt, and smaller particles are called

clay.


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Heavy/High Density Aggregate

having high specific gravity ranges

from 2.8 to 2.9 and bulk density from

2,800 to 2,900 kg/m3

.

i.e magnetite, hematite and barytes.

are not suitably graded.


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Lightweight aggregate

a particle density of less than 2,000 kg/m3.

subdivided into two groups :

- naturali.e (pumice, foamed lava, porous

limestone)

- artificiali.e (fly ash, steel slag, sintered slate)


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Physical Properties of

Aggregate

Strength

Deformation/modulus of elasticity

Toughness Hardness

Volume change

Porosity

Relative density


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Commonly the strength of aggregate

is in the range of 70 to 360 N/mm

2

.

Igneous rock are much stronger than

sedimentary and metamorphic rocks.

Strength of Aggregate


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Strength of Aggregate (contd)

The strength can be determined by :

Aggregate crushing value (ACV)

Aggregate impact value (AIV)

Ten percent fines value


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Deformation/Modulus of

Elasticity Can be determined by running the

compression test on specimen from

the parent rock.

Modulus of elasticity of concrete

increases with the increase ofaggregate modulus.


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Toughness of Aggregate

Defined as resistance to failure by impact.

Determined by Aggregate Impact Test.

Important for concrete used in roadpavement.


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Hardness

defined as resistance of an aggregate

to wear, load or applied pressure.

determined by an abrasion test.

important for concrete used in roadpavement


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Volume Change

change in the volume of the aggregate.

it is due to moisture movements inaggregates.

may result in a considerable shrinkageof the concrete.


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Relative Density

it is defined as the ratio of the

aggregates unit weight to that ofwater mix design.

it is important factor affecting thedensity of the resulting concrete.


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Porosity of aggregate

porosity of aggregate contributes to

the overall porosity of concrete.

Porosity = 100 WGs / (W+100) %where :

W is the water absorption (%)

Gs is the specific gravity on SSD


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Shape and Surface Texture

Shape and surface texture of aggregatescan affect the properties of concrete.

The external characteristics can be assessedby observation.


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Particle Shape Classification

(BS 812 : Part 1 : 1975)

Classification Description ShapesRounded Fully water-worn or

completely shaped

by attrition

River or seashore

gravel, desert,

seashore and wind-

blown sand.Irregular Naturally irregular or

partly shaped by

attrition and having

rounded edges

Other gravels, land

or dug flint

Flaky Material which the

thickness is small

relative to the other

two dimensions

Laminated rock


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Particle Shape Classification (contd)

(BS 812 : Part 1 : 1975)

Classification Description ShapeAngular Possessing well-defined

edges formed at the

intersection of roughly

planar faces

Crushed rocks of all

types, talus, crushed

slag.

Elongated Material usually angular,

in which the length is

considerably larger than

the other two dimensions

-

Flaky andelongated

Material having thelength considerably

larger than the width,

considerably larger than

the thickness

-

Source : Neville, A.M. (2002). Properties of Concrete, Prentice Hall,

S f T f A


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Surface Texture of Aggregates

Classification Description Examples

Glassy Conchoidal Fracture Black Flint, Vitreous

Slag

Smooth Water-worn, or

smooth due to thefracture of laminated

or fine-grained rock

Gravels, chert,

slate, marble, somerhyolites

Granular Fracture showingmore or less uniform

rounded grains

Sandstones, oolite

Source : Neville, A.M. (2002). Properties of Concrete, Prentice Hall,

England


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Water Absorption of Aggregate

(BS 812, ASTM C 127, EN 1097-6)

Water absorption of aggregate

as the weight of water absorbed

by an oven dry aggregate in

reaching the saturated andsurface dry condition.

is expressed as percentage of

the weight of the dry aggregate.


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Moisture content

is expressed as a percentage of the

weight increased of the saturated

surface dry aggregate.

water absorption represent the water

contained in the aggregate in the SSDcondition.


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Moisture content

moisture content is the water in

excess of that, the total water content

of a moist aggregate is equal to the

sum of absorption and moisture

content.


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Oven dry or bone dry

Four (4) conditions of moisture content

Air dryWet and damp

Moisture

Aggregate

Saturated and surface dry


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Grading of aggregate

can have considerable effect on theworkability and stability of concretemix.

The particle size distribution ofaggregate should be such that the

smaller particles fill the voidsbetween the larger particles.


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Particle size distribution

Dense andstrong

Unpacked andloose

Uneconomic


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Grading curve

(derived from BS 882)


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What happen if the grading

curve Lower than the specified grading

curve, the aggregate is coarser and

segregation of mix might take place.

Lies well above the specified curve,

the aggregate is finer and more waterwill be required, thus increasing the

cement content.


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What happen if the grading

curve . (contd) is steeper than the specified, it

indicates an excess of middle-size

particles and leads to harsh mix.

is flatter than the specified grading

curve, the aggregate will be deficientin middle size particles.


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Durability of Aggregate

Soundness of Aggregate

Alkali-aggregate reaction

Thermal properties

Deleterious substance (clay, silt,

decayed vegetable, salt, unsound

particles, etc.)


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Admixtures

as materials or substances other thanaggregates, cement and water whichare added to the concrete batchimmediately before or during mixing.

it is used to modify or improve one or

more of its properties in the plastic orhardened state.


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Types of admixture

Chemical Admixtures

Mineral Admixtures

Bonding Admixtures

Water-Repellent Admixtures


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Chemical admixtures

Retarders

Accelerators

Water reducers or plasticisers

Air entraining

Ch i l d i t


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Chemical admixtures

(Retarders)

retarders delay the setting andhardening of concrete.

it is used in hot weather concreting.

calcium sulphate (gypsum) is addedduring the manufacture of cement toretard the setting.

Chemical admixtures


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Chemical admixtures

(Accelerator)

The chemicals used to accelerate the settingand hardening of concrete.

The most commonly used accelerator iscalcium chloride.

The disadvantages of using accelerators isthat it may lead to corrosion of steelreinforcement.

Effect of Accelerator on the


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Effect of Accelerator on thecompressive strength

Ch i l d i


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Chemical admixtures

(Water Reducers or Plasticisers)

It is used to increase the workability of

concrete without increasing water content.

A typical water reducing admixture is

made from the metallic salts,

lignosulphonic acids, carbohydrates andorganic acids.


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Chemical admixtures

(Superplasticisers) will impart very high workability or allows a largedecrease in water content for a given workability.

as a means of producing flowing concrete withoutundesirable seggregation.

useful to place concrete where the reinforcement isheavily congested.


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Chemical admixtures

(Air entrained) used to entrain air in the form of very small

disconnected air bubbles in concrete.

It increases the workability and decreases

the bleeding and seggregation.

It improves the resistance of concrete to

frost under cold climatic conditions.


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Mineral admixtures

fly ash

silica fume

slag


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Other admixtures

bonding admixture

water-repellent admixtures

curing agent


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HOMEWORK

Search the standard procedures to conductAIV, ACV and ten percent fine tests todetermine the strength of aggregate.

a. Briefly elaborate the procedures.

b. Compare and contrast the three(3)

tests.

Concrete Construction(Week1&2)

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